Understanding the fundamental nature of dark matter (DM) — its cosmological origin, constituents, and interactions — is one of the most important questions in fundamental science today. In this thesis, I present two novel and highly complementary approaches to cover the gaps in sensitivity of current DM searches. The searches are enabled by a first-of-its-kind reconstruction technique to search for hidden-sector particles using the Compact Muon Solenoid (CMS) and by new advances in quantum sensing technology to search for axions and hidden-sector DM.
\r\n\r\nIn the first part of this thesis, I present a search for long-lived hidden sector particles, predicted by many extensions of the SM, using a novel technique to reconstruct decays of long-lived particles (LLPs) in the CMS muon detector. The innovative LLP reconstruction technique is sensitive to a broad range of LLP decays and to LLP masses below GeV. The search yields competitive sensitivity for proper lifetime 0.1 - 1000 m with the full Run 2 dataset recorded at the LHC between 2016 - 2018 at √s = 13 TeV. To extend the physics reach of this novel muon detector shower (MDS) signature, I present the model-independence of MDS and the reinterpretation of the search to a large number of LLP models, demonstrating its complementarity with proposed and existing dedicated LLP experiments. Finally, I present a new dedicated MDS trigger that improves the trigger efficiency by at least an order of magnitude and was deployed in 2022, at the start of Run 3 of the LHC operations.
\r\n\r\nIn the second part of the thesis, I present for the first time, the use of a novel quantum sensor, the low-noise and single-photon sensitive superconducting nanowire single photon detectors (SNSPDs), to directly detect dark matter. The low detection threshold and ultra-low dark count rate of SNSPDs can close the gap in DM discovery reach due to the current limitations in detector sensitivity. I will present my work on the development and characterization of SNSPDs for two entirely new experiments to directly detect axions via absorption and hidden-sector DM via electron scattering. The search for axions employs a novel broadband reflector technique with the Broadband Reflector Experiment for Axion Detection (BREAD). A unique parabolic mirror is then used to focus axion-converted photons to the SNSPDs, extending the reach to axion masses of 0.04 - 1 eV. On the other hand, by coupling the SNSPDs with gallium arsenide, a bright cryogenic scintillator well matched to SNSPD detection, a prototype sensing system can be built as a basis of new direct DM detection experiments capable of extending the discovery to DM masses as low as 1 MeV.
", "doi": "10.7907/ta74-mz22", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16290", "collection": "thesis", "collection_id": "16290", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02092024-210936211", "type": "thesis", "title": "Quantum Measurements with Superconducting Nanowire Single Photon Detectors", "author": [ { "family_name": "Mueller", "given_name": "Andrew Sterling", "orcid": "0000-0002-6598-9732", "clpid": "Mueller-Andrew- Sterling" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Shaw", "given_name": "Matthew D.", "clpid": "Shaw-M-D" } ], "thesis_committee": [ { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Shaw", "given_name": "Matthew D.", "clpid": "Shaw-M-D" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Superconducting Nanowire Single-Photon Detectors (SNSPDs) are high-performance photon counting detectors, typically operated just a few degrees above absolute zero. Comprising a current-biased nanowire transitioning between superconducting and resistive states upon photon absorption, SNSPDs generate voltage pulses for precise photon arrival time measurement. Initially demonstrated in the 1990s, SNSPDs are now mature devices widely employed in various fields, including space communication, biological imaging, and quantum technology. This\u00a0thesis\u00a0explores techniques to enhance usable count rate, dark count rate, timing resolution, and photon number resolution for both emerging and established SNSPD designs. We introduce a free space optical filtering method to minimize SNSPD dark count rates which is competitive with the state-of-the-art for fiber coupled SNSPDs, and especially impactful for space communication applications. We go on to study dynamics that limit SNSPD maximum count rates, presenting a calibration and in-situ correction procedure to significantly reduce jitter at high rates without additional hardware or offline processing. With an eye towards space communication applications beyond NASA's Deep Space Optical Communication (DSOC) project, we present a high-rate Pulse Position Modulation communication demo with SNSPDs. In the process we uncover a rich photon-number dependent response in these detectors and devise methods to properly leverage and manage it. Finally, we employ low-jitter SNSPDs in a high-rate entanglement distribution system, achieving high entanglement visibilities, and distillable entanglement rates. \u00a0As this work focuses on optimizing SNSPD usage and analysis rather than device physics or fabrication, it is broadly applicable to any users of this single photon detection technology.
", "doi": "10.7907/tneb-9z27", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16290", "collection": "thesis", "collection_id": "16290", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02092024-210936211", "type": "thesis", "title": "Quantum Measurements with Superconducting Nanowire Single Photon Detectors", "author": [ { "family_name": "Mueller", "given_name": "Andrew Sterling", "orcid": "0000-0002-6598-9732", "clpid": "Mueller-Andrew- Sterling" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Shaw", "given_name": "Matthew D.", "clpid": "Shaw-M-D" } ], "thesis_committee": [ { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Shaw", "given_name": "Matthew D.", "clpid": "Shaw-M-D" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Superconducting Nanowire Single-Photon Detectors (SNSPDs) are high-performance photon counting detectors, typically operated just a few degrees above absolute zero. Comprising a current-biased nanowire transitioning between superconducting and resistive states upon photon absorption, SNSPDs generate voltage pulses for precise photon arrival time measurement. Initially demonstrated in the 1990s, SNSPDs are now mature devices widely employed in various fields, including space communication, biological imaging, and quantum technology. This\u00a0thesis\u00a0explores techniques to enhance usable count rate, dark count rate, timing resolution, and photon number resolution for both emerging and established SNSPD designs. We introduce a free space optical filtering method to minimize SNSPD dark count rates which is competitive with the state-of-the-art for fiber coupled SNSPDs, and especially impactful for space communication applications. We go on to study dynamics that limit SNSPD maximum count rates, presenting a calibration and in-situ correction procedure to significantly reduce jitter at high rates without additional hardware or offline processing. With an eye towards space communication applications beyond NASA's Deep Space Optical Communication (DSOC) project, we present a high-rate Pulse Position Modulation communication demo with SNSPDs. In the process we uncover a rich photon-number dependent response in these detectors and devise methods to properly leverage and manage it. Finally, we employ low-jitter SNSPDs in a high-rate entanglement distribution system, achieving high entanglement visibilities, and distillable entanglement rates. \u00a0As this work focuses on optimizing SNSPD usage and analysis rather than device physics or fabrication, it is broadly applicable to any users of this single photon detection technology.
", "doi": "10.7907/tneb-9z27", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:15230", "collection": "thesis", "collection_id": "15230", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302023-084739008", "type": "thesis", "title": "A Deep Dive into the Connections Between the Renormalization Group and Deep Learning in the Ising Model", "author": [ { "family_name": "Taylor", "given_name": "Kelsie", "orcid": "0009-0001-7510-2306", "clpid": "Taylor-Kelsie-Reed" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Lykken", "given_name": "Joseph", "orcid": "0000-0002-0090-9439", "clpid": "Lykken-J" } ], "thesis_committee": [ { "family_name": "Libbrecht", "given_name": "Kenneth George", "orcid": "0000-0002-8744-3298", "clpid": "Libbrecht-K-G" }, { "family_name": "Politzer", "given_name": "Hugh David", "orcid": "0000-0002-4983-6621", "clpid": "Politzer-H-D" }, { "family_name": "Alicea", "given_name": "Jason F.", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Filippone", "given_name": "Bradley W.", "orcid": "0000-0002-2618-2688", "clpid": "Filippone-B-W" }, { "family_name": "Frautschi", "given_name": "Steven C.", "clpid": "Frautschi-S-C" }, { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" }, { "family_name": "Chatziioannou", "given_name": "Katerina", "orcid": "0000-0002-5833-413X", "clpid": "Chatziioannou-K" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "The renormalization group (RG) is an essential technique in statistical physics and quantum field theory, which considers scale-invariant properties of physical theories and how these theories\u2019 parameters change with scaling. Deep learning is a powerful computational technique that uses multi-layered neural networks to solve a myriad of complicated problems. Previous research suggests the possibility that unsupervised deep learning may be a form of RG flow, by being a layer-by-layer coarse graining of the original data. We examined this connection on a more rigorous basis for the simple example of Kadanoff block renormalization of the 2D nearest-neighbor Ising model, with our deep learning accomplished via Restricted Boltzmann Machines (RBMs). We developed extensive renormalization techniques for the 1D and 2D Ising model to provide a baseline for comparison. For the 1D Ising model, we successfully used Adam optimization on a correlation length loss function to learn the group flow; yielding results consistent with the analytical model for infinite N. For the 2D Ising model, we successfully generated Ising model samples using the Wolff algorithm, and performed the group flow using a quasi-deterministic method, validating these results by calculating the critical exponent \\nu. We then examined RBM learning of the Ising model layer by layer, finding a blocking structure in the learning that is qualitatively similar to RG. Lastly, we directly compared the weights of each layer from the learning to Ising spin renormalization, but found quantitative inconsistencies for the simple case of nearest-neighbor Ising models.", "doi": "10.7907/ztpg-z092", "publication_date": "2023", "thesis_type": "senior_major", "thesis_year": "2023" }, { "id": "thesis:15019", "collection": "thesis", "collection_id": "15019", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09132022-001004681", "primary_object_url": { "basename": "olmo_cerri_2023_thesis.pdf", "content": "final", "filesize": 18734075, "license": "other", "mime_type": "application/pdf", "url": "/15019/1/olmo_cerri_2023_thesis.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "New Physics Tools for Discovery, a New Era of Timing Detector, and Lepton Flavor Universality Test at CMS", "author": [ { "family_name": "Cerri", "given_name": "Olmo", "orcid": "0000-0002-2191-0666", "clpid": "Cerri-Olmo" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" }, { "family_name": "Cheung", "given_name": "Clifford W.", "orcid": "0000-0002-9983-9425", "clpid": "Cheung-Clifford" }, { "family_name": "Patterson", "given_name": "Ryan B.", "orcid": "0000-0002-5787-9517", "clpid": "Patterson-R-B" }, { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "The field of particle and fundamental physics finds itself now in a peculiar situation. The established Standard Model accurately predicts most of the observations, but several compelling reasons motivate a need for an extension of the current theory. In this thesis, I focus my research on facing the current situation of the field in a diversified threefold manner.
\r\n\r\nFirst, I develop methods based on physics-driven machine learning algorithms, with a particular focus on developing a model-independent tagger for unexpected events using artificial neural networks. This study shows how model-independent new physics triggers, possibly trained on real data, can select a low rate stream of events able to explore new physics processes up to a 10-100 pb cross section and can create a special dataset of rare unexpected events. Other important results from this body of work include the first application of the proposed anomaly detection strategy to real data, the use of graph neural networks to improve current pileup mitigation algorithms, the development of jet taggers based on the interaction network, and analysis-specific fast simulation.
\r\n\r\nSecond, I focus on the methodological and hardware development of the MIP Timing Layer that is expected to upgrade CMS in preparation for HL-LHC. My seminal study demonstrates the possibility of using time-of-flight information to perform particle identification, which has a significant impact on heavy stable charged particle searches. This work introduces how to measure time-of-flight at CMS, a strategy for particle identification, and an algorithm to locate vertices in space and time. I also participated in the sensor testing and test beam operation. In particular, I conducted a study about the design and prototype of the detector modules' thermal behavior that shows how different geometries could lead to cooling differences of a few K.
\r\n\r\nLast, I direct my attention towards CMS's first lepton flavor universality tests with B meson decays. Using a dataset acquired thanks to a custom design trigger, I independently develop the measurement of the R(D*) ratio, a parameter whose tensions between the predictions and observation have drawn remarkable attentions. I oversaw the complete mature state of the analysis, from the Monte Carlo simulation to the fitting procedure. Further collaboration-wide efforts are still required, but I demonstrate the expected sensitivity of about 15% using an Asimov dataset.
", "doi": "10.7907/bqsn-sp82", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15034", "collection": "thesis", "collection_id": "15034", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09252022-195535688", "type": "thesis", "title": "Rare Higgs Processes at CMS and Precision Timing Detector Studies for HL-LHC CMS Upgrade", "author": [ { "family_name": "Dutta", "given_name": "Irene", "orcid": "0000-0003-0953-4503", "clpid": "Dutta-Irene" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Patterson", "given_name": "Ryan B.", "orcid": "0000-0002-5787-9517", "clpid": "Patterson-R-B" }, { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" }, { "family_name": "Filippone", "given_name": "Bradley W.", "orcid": "0000-0002-2618-2688", "clpid": "Filippone-B-W" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis describes the search for two rare Higgs processes. The first analysis describes the CMS Run 2 search for
The second analysis describes the CMS Run 2 search for
Finally, this thesis also discusses the planned MIP Timing Detector (MTD) upgrade for CMS at the HL-LHC. The MTD will be a time-of-flight (TOF) detector, designed to provide a precision timing information for charged particles using SiPMs + LYSO scintillating crystals, with a time resolution of ~30 ps. This thesis describes several R&D tests that have been performed for characterizing the sensor properties (time resolution, light yield, etc.) and optimizing the sensor design geometry. This thesis also contains a description of mock test setups for cooling the sensors, since it is known to be an effective way of mitigating the increased dark current rates in the sensors due to radiation damage.
", "doi": "10.7907/tmt4-nq20", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15237", "collection": "thesis", "collection_id": "15237", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302023-234037855", "type": "thesis", "title": "Search for Supersymmetry Using Higgs Boson to Diphoton Decays and Search for Long-Lived Particles Using Out-of-Time Trackless Jets at \u221as = 13 TeV", "author": [ { "family_name": "Mao", "given_name": "Jiajing", "orcid": "0009-0002-8988-9987", "clpid": "Mao-Jiajing" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" }, { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "The thesis describes two searches conducted at the Large Hadron Collider with a center-of-mass energy of 13 TeV, using proton-proton collison data collected by the CMS experiment. The supersymmetry (SUSY) search focus on the production of at least one Higgs boson that decays into two photons in the decay chains of pair-produced SUSY particles. The data used has an integrated luminosity of 77.5 fb\u207b\u00b9. The events are classified into different search regions based on charged leptons, Higgs boson candidates, and kinematic variables to make them sensitive to different SUSY scenarios. The results reveal no statistically significant excess of events compared to the standard model predictions. The searches exclude bottom squark pair production for bottom squark masses below 510 GeV and a lightest SUSY particle mass of 1 GeV. The wino-like chargino-neutralino production in gauge-mediated SUSY breaking (GMSB) is excluded for chargino and neutralino masses below 235 GeV, with a gravitino mass of 1 GeV. Furthermore, the higgsino-like chargino-neutralino production in GMSB, where the neutralino decays exclusively to a Higgs boson and a gravitino, is excluded for neutralino masses below 290 GeV. The thesis also reports a search for long-lived particles that decay in the outer regions of the CMS silicon tracker or in the calorimeters. The search uses data with an integrated luminosity of 138 fb\u207b\u00b9. The identification of long-lived particle decays utilizes a novel technique that combines nearly trackless and out-of-time jet information into a deep neural network discriminator. The results are interpreted using a simplified GMSB model of chargino-neutralino production, where the neutralino is the next-to-lightest supersymmetric particle that decays to a gravitino and either a Higgs or Z boson. The search achieves the highest sensitivity for neutralino proper decay lengths of approximately 0.5 meters and excludes masses up to 1.18 TeV at a 95\\% confidence level. This search represents the most stringent constraint to date in the mass range from the kinematic limit imposed by the Higgs boson mass up to 1.8 TeV.
", "doi": "10.7907/pwpe-ef70", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:16065", "collection": "thesis", "collection_id": "16065", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022023-203550284", "type": "thesis", "title": "Measuring Fundamental Symmetry Violation in Polyatomic Molecules", "author": [ { "family_name": "Jadbabaie", "given_name": "Arian", "orcid": "0000-0002-7606-5586", "clpid": "Jadbabaie-Arian" } ], "thesis_advisor": [ { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" } ], "thesis_committee": [ { "family_name": "Filippone", "given_name": "Bradley W.", "orcid": "0000-0002-2618-2688", "clpid": "Filippone-B-W" }, { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" }, { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Open questions in fundamental physics, such as the cosmological origins of the observed imbalance of matter and antimatter, motivate the search for fundamental symmetry violating physics beyond the Standard Model (BSM). Recent measurements of heavy, polar, diatomic molecules constrain the existence of new, Parity (P) and Time-reversal (T) violating physics at 10-50 TeV energy scales, exceeding the reach of particle colliders. The power of existing molecular measurements motivates us to pursue the next-generation of searches for symmetry violation. By adopting polyatomic molecules as an experimental platform, we can generically combine laser-cooling and trapping, BSM sensitivity, and exquisite quantum control over P and/or T violating energy shifts. These improvements are projected to increase the sensitivity of measurements to the PeV energy scale. In this thesis, we develop the foundations for new physics searches using cold and ultracold, linear triatomic molecules. These molecules have long-lived vibrational bending modes with closely spaced, opposite parity doublets, a key structure that aids polarizability, molecule control, state engineering, and systematic suppression. We produce a cryogenic buffer gas beam of cold YbOH molecules, using laser-enhanced chemical reactions to increase molecular yield by an order of magnitude. As a prerequisite for precision measurements, we perform high-resolution spectroscopic characterization of both the ground and excited bending modes of YbOH. Next, we present detailed tests of quantum state preparation and readout protocols in a YbOH beam, successfully demonstrating Ramsey interferometry using two-photon transitions. Finally, as part of the PolyEDM collaboration, we illustrate the power of polyatomic molecules by combining laser cooling and optical trapping with quantum state engineering to perform proof-of-principle measurements of P,T violating physics in magnetically-insensitive states of ultracold CaOH molecules at Harvard University. Our results open the door to a wide range of quantum-enhanced symmetry violation searches benefiting from the unique structural features of polyatomic molecules.
", "doi": "10.7907/2jry-1s28", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:14995", "collection": "thesis", "collection_id": "14995", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08062022-012526440", "primary_object_url": { "basename": "Pilgram_Nickolas_2023.pdf", "content": "final", "filesize": 19380483, "license": "other", "mime_type": "application/pdf", "url": "/14995/1/Pilgram_Nickolas_2023.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Production and Characterization of Ytterbium Monohydroxide (YbOH) for Next-Generation Parity and Time-Reversal Violating Physics Searches", "author": [ { "family_name": "Pilgram", "given_name": "Nickolas Hovanec", "orcid": "0000-0002-5467-3783", "clpid": "Pilgram-Nickolas-Hovanec" } ], "thesis_advisor": [ { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" } ], "thesis_committee": [ { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" }, { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Filippone", "given_name": "Bradley W.", "orcid": "0000-0002-2618-2688", "clpid": "Filippone-B-W" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "New sources of parity (P) and time-reversal (T) violating physics are motivated by several unanswered questions in fundamental physics, including the observed imbalance between matter and anti-matter in the universe. P,T-violating effects can induce permanent electric dipole moments (EDMs) in atoms and molecules, allowing them to act as sensitive probes of new physics. The linear, triatomic molecule ytterbium monohydroxide (YbOH) has emerged as a promising candidate for next-generation molecular EDM searches, because it possesses both an electronic structure amenable to optical cycling and parity doublets in the bending mode. These features enable laser cooling, highly polarizable science states, and internal comagnetometry which promises an order-of-magnitude improvement to current EDM sensitivities. Additionally, different isotoplogues of YbOH offer sensitivity to different sources of P,T-violating physics: leptonic sources via a measurement of the electron\u2019s EDM in 174YbOH and hadronic sources via a measurement of the nuclear magnetic quadrupole moment (NMQM) of the 173Yb nucleus in 173YbOH. In this dissertation, I describe the design, construction, and optimization of a YbOH cryogenic buffer gas beam (CBGB) source, including the implementation of laser-enhanced chemical reactions for increased molecular production. Direct and frequency modulated (FM) absorption spectroscopy and laser-induced fluorescence measurements (LIF) were implemented in the CBGB source, and LIF and separated field pump/probe microwave optical double resonance spectroscopy was conducted in a supersonic molecular beam source. Additionally, laser-enhanced chemical reactions were utilized to develop a novel spectroscopic technique critical to the observation of the spectrum of the odd isotopologues. FM absorption spectroscopy in the CBGB source allowed the observation of the previously unobserved, weak Ã2Π1/2(1,0,0)-X̃2Σ+(3,0,0), [17.68], and [17.64] vibronic bands. The X̃2Σ+(0,0,0) ground state has been characterized at high precision and the Ã2Π1/2(1,0,0)-X̃2Σ+(3,0,0) band of 174YbOH and the Ã2Π1/2(0,0,0)-X̃2Σ+(0,0,0) band of the odd 171,173YbOH isotopologues have been characterized for the first time. This work provides much of the spectroscopic knowledge needed to implement next-generation P,T-violating physics searches in YbOH.", "doi": "10.7907/05m0-4g74", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15230", "collection": "thesis", "collection_id": "15230", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302023-084739008", "type": "thesis", "title": "A Deep Dive into the Connections Between the Renormalization Group and Deep Learning in the Ising Model", "author": [ { "family_name": "Taylor", "given_name": "Kelsie", "orcid": "0009-0001-7510-2306", "clpid": "Taylor-Kelsie-Reed" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Lykken", "given_name": "Joseph", "orcid": "0000-0002-0090-9439", "clpid": "Lykken-J" } ], "thesis_committee": [ { "family_name": "Libbrecht", "given_name": "Kenneth George", "orcid": "0000-0002-8744-3298", "clpid": "Libbrecht-K-G" }, { "family_name": "Politzer", "given_name": "Hugh David", "orcid": "0000-0002-4983-6621", "clpid": "Politzer-H-D" }, { "family_name": "Alicea", "given_name": "Jason F.", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Filippone", "given_name": "Bradley W.", "orcid": "0000-0002-2618-2688", "clpid": "Filippone-B-W" }, { "family_name": "Frautschi", "given_name": "Steven C.", "clpid": "Frautschi-S-C" }, { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" }, { "family_name": "Chatziioannou", "given_name": "Katerina", "orcid": "0000-0002-5833-413X", "clpid": "Chatziioannou-K" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "The renormalization group (RG) is an essential technique in statistical physics and quantum field theory, which considers scale-invariant properties of physical theories and how these theories\u2019 parameters change with scaling. Deep learning is a powerful computational technique that uses multi-layered neural networks to solve a myriad of complicated problems. Previous research suggests the possibility that unsupervised deep learning may be a form of RG flow, by being a layer-by-layer coarse graining of the original data. We examined this connection on a more rigorous basis for the simple example of Kadanoff block renormalization of the 2D nearest-neighbor Ising model, with our deep learning accomplished via Restricted Boltzmann Machines (RBMs). We developed extensive renormalization techniques for the 1D and 2D Ising model to provide a baseline for comparison. For the 1D Ising model, we successfully used Adam optimization on a correlation length loss function to learn the group flow; yielding results consistent with the analytical model for infinite N. For the 2D Ising model, we successfully generated Ising model samples using the Wolff algorithm, and performed the group flow using a quasi-deterministic method, validating these results by calculating the critical exponent \\nu. We then examined RBM learning of the Ising model layer by layer, finding a blocking structure in the learning that is qualitatively similar to RG. Lastly, we directly compared the weights of each layer from the learning to Ising spin renormalization, but found quantitative inconsistencies for the simple case of nearest-neighbor Ising models.", "doi": "10.7907/ztpg-z092", "publication_date": "2023", "thesis_type": "senior_major", "thesis_year": "2023" }, { "id": "thesis:14380", "collection": "thesis", "collection_id": "14380", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10012021-210141406", "type": "thesis", "title": "Searches for Nonresonant Higgs Boson Pair Production and Long-Lived Particles at the LHC and Machine-Learning Solutions for the High-Luminosity LHC Era", "author": [ { "family_name": "Nguyen", "given_name": "Thong Quang", "orcid": "0000-0003-3954-5131", "clpid": "Nguyen-Thong-Quang" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Cheung", "given_name": "Clifford W.", "orcid": "0000-0002-9983-9425", "clpid": "Cheung-Clifford" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis presents two physics analyses using 137 fb\u22121 proton-proton collision data collected by the CMS experiment at \u221as = 13 TeV, along with a series of machine-learning solutions to extend the physics program at the LHC and to address the computational challenges in the High-Luminosity LHC era. The first analysis searches for nonresonant Higgs boson pair production in final states with two photons and two bottom quarks, with no significant deviation from the background-only hypothesis observed. The observed (expected) upper limit on the product of the Higgs boson pair production cross section and branching fraction into bb̅\u03b3\u03b3 is 0.67 (0.45) fb, corresponding to 7.7 (5.2) times the Standard Model prediction. The modifier of the Higgs trilinear self-coupling is constrained within the range -3.3 < \u03ba\u03bb < 8.5. The modifier for coupling between a pair of Higgs bosons and a pair of vector bosons, along with the 2-dimensional constraint of the modifiers of Higgs self-coupling and Yukawa coupling, are also reported. A graph-based algorithm to identify boosted H \u2192 bb̅ jets to improve future Higgs search is presented. The second analysis searches for long-lived supersymmetry particles decaying to photons and gravitinos in the context of gauge-mediated supersymmetry breaking model. Results are presented in terms of 95% confidence level expected exclusion limits on the masses and proper decay lengths of the neutralino, which exceed the limits from the previous searches by up to 100 GeV for the neutralino mass and by five times for the neutralino proper decay length. A strategy for model-independent new physics searches is presented with an anomaly trigger based on unsupervised learning algorithms that can be deployed in both the high-level trigger and the Level-1 trigger in CMS. Three other machine-learning solutions are presented to address the computational challenges in the HL-LHC era: a layer based on multi-modal deep neural networks that can reduce the false-positive events selected by the trigger by over one order of magnitude while retaining 99% of signal events, a full-event simulation algorithm based on recurrent generative adversarial networks that has potential to replace traditional simulation method while being five orders of magnitude faster, and a fast simulation algorithm for specific analyses based on encoder-decoder architecture that would result in about an order-of-magnitude reduction in computing and storage requirements for the collision simulation workflow.
", "doi": "10.7907/knfz-q495", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:15035", "collection": "thesis", "collection_id": "15035", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09272022-143825909", "primary_object_url": { "basename": "Senior_thesis.pdf", "content": "final", "filesize": 4758015, "license": "other", "mime_type": "application/pdf", "url": "/15035/1/Senior_thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Quantum Computing for Machine Learning and Physics Simulation", "author": [ { "family_name": "Zlokapa", "given_name": "Alexander", "orcid": "0000-0002-4153-8646", "clpid": "Zlokapa-Alexander" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Libbrecht", "given_name": "Kenneth George", "orcid": "0000-0002-8744-3298", "clpid": "Libbrecht-K-G" }, { "family_name": "Kapustin", "given_name": "Anton N.", "orcid": "0000-0003-3903-5158", "clpid": "Kapustin-A" }, { "family_name": "Alicea", "given_name": "Jason F.", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Kimble", "given_name": "H. Jeff", "clpid": "Kimble-H-J" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Quantum computing is widely thought to provide exponential speedups over classical algorithms for a variety of computational tasks. In classical computing, methods in artificial intelligence such as neural networks and adversarial learning have enabled drastic improvements in state-of-the-art performance for a variety of tasks. We consider the intersection of quantum computing with machine learning, including the quantum algorithms for deep learning on classical datasets, quantum adversarial learning for quantum states, and variational quantum machine learning for improved physics simulation.
\r\n \r\nWe consider a standard deep neural network architecture and show that conditions amenable to trainability by gradient descent coincide with those necessary for an efficient quantum algorithm. Considering the neural network in the infinite-width limit using the neural tangent kernel formalism, we propose a quantum algorithm to train the neural network with vanishing error as the training dataset size increases. Under a sparse approximation of the neural tangent kernel, the training time scales logarithmically with the number of training examples, providing the first known exponential quantum speedup for feedforward neural networks. Related approximations to the neural tangent kernel are discussed, with numerical studies showing successful convergence beyond the proven regime. Our work suggests the applicability of the quantum computing to additional neural network architectures and common datasets such as MNIST, as well as kernel methods beyond the neural tangent kernel.
\r\n \r\nGenerative adversarial networks (GANs) are one of the most widely adopted machine learning methods for data generation. We propose an entangling quantum GAN (EQ-GAN) that overcomes some limitations of previously proposed quantum GANs. EQ-GAN guarantees the convergence to a Nash equilibrium under minimax optimization of the discriminator and generator circuits by performing entangling operations between both the generator output and true quantum data. We show that EQ-GAN has additional robustness against coherent errors and demonstrate the effectiveness of EQ-GAN experimentally in a Google Sycamore superconducting quantum processor. By adversarially learning efficient representations of quantum states, we prepare an approximate quantum random access memory and demonstrate its use in applications including the training of near-term quantum neural networks.
\r\n \r\nWith quantum computers providing a natural platform for physics simulation, we investigate the use of variational quantum circuits to simulate many-body systems with high fidelity in the near future. In particular, recent work shows that teleportation caused by introducing a weak coupling between two entangled SYK models is dual to a particle traversing an AdS-Schwarzschild wormhole, providing a mechanism to probe quantum gravity theories in the lab. To simulate such a system, we propose the process of compressed Trotterization to improve the fidelity of time evolution on noisy devices. The task of learning approximate time evolution circuits is shown to have a favorable training landscape, and numerical experiments demonstrate its relevance to simulating other many-body systems such as a Fermi-Hubbard model. For the SYK model in particular, we demonstrate the construction of a low-rank approximation that favors a shallower Trotterization. Finally, classical simulations of finite-N SYK models suggest that teleportation via a traversable wormhole instead of random unitary scrambling is achievable with O(20) qubits, providing further indication that such quantum gravity experiments may realizable with near-term quantum hardware.
", "doi": "10.7907/q75q-zm20", "publication_date": "2021", "thesis_type": "senior_major", "thesis_year": "2021" }, { "id": "thesis:14051", "collection": "thesis", "collection_id": "14051", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01122021-051424539", "primary_object_url": { "basename": "Zhang_Zhicai_2021.pdf", "content": "final", "filesize": 32035046, "license": "other", "mime_type": "application/pdf", "url": "/14051/1/Zhang_Zhicai_2021.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "First Observation of the Production of Three Massive Vector Bosons and Search for Long-Lived Particles using Delayed Photons in pp Collisions at \u221as = 13 TeV", "author": [ { "family_name": "Zhang", "given_name": "Zhicai", "orcid": "0000-0002-1630-0986", "clpid": "Zhang-Zhicai" } ], "thesis_advisor": [ { "family_name": "Newman", "given_name": "Harvey B.", "orcid": "0000-0003-0964-1480", "clpid": "Newman-H-B" } ], "thesis_committee": [ { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" }, { "family_name": "Newman", "given_name": "Harvey B.", "orcid": "0000-0003-0964-1480", "clpid": "Newman-H-B" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Filippone", "given_name": "Bradley W.", "orcid": "0000-0002-2618-2688", "clpid": "Filippone-B-W" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis presents the first observation of the production of three massive vector bosons (VVV with V= W, Z) in proton-proton collisions at the LHC at \u221as = 13 TeV. The search was performed in final states with two same-sign charged leptons (electrons or muons) plus one or two jets, and three, four, five, or six leptons from WWW, WWZ, WZZ and ZZZ decays, with a data sample corresponding to an integrated luminosity of 137 fb-1 collected by the CMS experiment during 2016-2018. The observed (expected) significance of the combined VVV production is 5.7 (5.9) standard deviations, and the production cross section is measured to be 1010+210-200(stat)+150-120(syst) fb, corresponding to a signal strength of 1.02+0.26-0.23. We also found evidence for WWW and for WWZ production, with observed significances of 3.3 and 3.4 standard deviations, respectively. The measured production cross sections for individual VVV processes are also reported. The establishment of VVV production opens a new program of many standard model studies (such as gauge-gauge and Higgs-gauge couplings), and provides a new tool for many new physics searches (such as anomalous gauge coupling searches, new resonance searches). This thesis also reports a search for long-lived supersymmetry particles decaying to photons in proton-proton collisions at the LHC at \u221as = 13 TeV, with a data sample corresponding to an integrated luminosity of 77.4fb-1 collected by CMS during 2016-2017. Results are interpreted with a gauge-mediated supersymmetry breaking model, where the long-lived particle is a neutralino and the lightest supersymmetry particle is a gravitino. For neutralino proper decay lengths of 0.1, 1, 10, and 100 m, masses up to 320, 525, 360, and 215 GeV are excluded at 95% confidence level, respectively. This result extends the limits from previous searches by one order of magnitude for the neutralino proper decay length and up to 100 GeV more for the neutralino mass. Motivated by the need for precision timing measurements for long-lived particle searches, as well as for improvements in general object reconstruction performance, the timing performance of two types of sensors are studied in this thesis: one with a Cerium doped Lutetium Yttrium Orthosilicate (LYSO:Ce) crystal as the scintillator and a silicon photomultiplier (SiPM) as the photodetector, another with a Cadmium-Telluride sensor as the active material for a sampling calorimeter. Both setups have been demonstrated with test beams to be able to provide timing measurements of particles with a resolution below 30 ps.
", "doi": "10.7907/vnec-zj29", "publication_date": "2021-01", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:15035", "collection": "thesis", "collection_id": "15035", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09272022-143825909", "primary_object_url": { "basename": "Senior_thesis.pdf", "content": "final", "filesize": 4758015, "license": "other", "mime_type": "application/pdf", "url": "/15035/1/Senior_thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Quantum Computing for Machine Learning and Physics Simulation", "author": [ { "family_name": "Zlokapa", "given_name": "Alexander", "orcid": "0000-0002-4153-8646", "clpid": "Zlokapa-Alexander" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Libbrecht", "given_name": "Kenneth George", "orcid": "0000-0002-8744-3298", "clpid": "Libbrecht-K-G" }, { "family_name": "Kapustin", "given_name": "Anton N.", "orcid": "0000-0003-3903-5158", "clpid": "Kapustin-A" }, { "family_name": "Alicea", "given_name": "Jason F.", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Kimble", "given_name": "H. Jeff", "clpid": "Kimble-H-J" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Quantum computing is widely thought to provide exponential speedups over classical algorithms for a variety of computational tasks. In classical computing, methods in artificial intelligence such as neural networks and adversarial learning have enabled drastic improvements in state-of-the-art performance for a variety of tasks. We consider the intersection of quantum computing with machine learning, including the quantum algorithms for deep learning on classical datasets, quantum adversarial learning for quantum states, and variational quantum machine learning for improved physics simulation.
\r\n \r\nWe consider a standard deep neural network architecture and show that conditions amenable to trainability by gradient descent coincide with those necessary for an efficient quantum algorithm. Considering the neural network in the infinite-width limit using the neural tangent kernel formalism, we propose a quantum algorithm to train the neural network with vanishing error as the training dataset size increases. Under a sparse approximation of the neural tangent kernel, the training time scales logarithmically with the number of training examples, providing the first known exponential quantum speedup for feedforward neural networks. Related approximations to the neural tangent kernel are discussed, with numerical studies showing successful convergence beyond the proven regime. Our work suggests the applicability of the quantum computing to additional neural network architectures and common datasets such as MNIST, as well as kernel methods beyond the neural tangent kernel.
\r\n \r\nGenerative adversarial networks (GANs) are one of the most widely adopted machine learning methods for data generation. We propose an entangling quantum GAN (EQ-GAN) that overcomes some limitations of previously proposed quantum GANs. EQ-GAN guarantees the convergence to a Nash equilibrium under minimax optimization of the discriminator and generator circuits by performing entangling operations between both the generator output and true quantum data. We show that EQ-GAN has additional robustness against coherent errors and demonstrate the effectiveness of EQ-GAN experimentally in a Google Sycamore superconducting quantum processor. By adversarially learning efficient representations of quantum states, we prepare an approximate quantum random access memory and demonstrate its use in applications including the training of near-term quantum neural networks.
\r\n \r\nWith quantum computers providing a natural platform for physics simulation, we investigate the use of variational quantum circuits to simulate many-body systems with high fidelity in the near future. In particular, recent work shows that teleportation caused by introducing a weak coupling between two entangled SYK models is dual to a particle traversing an AdS-Schwarzschild wormhole, providing a mechanism to probe quantum gravity theories in the lab. To simulate such a system, we propose the process of compressed Trotterization to improve the fidelity of time evolution on noisy devices. The task of learning approximate time evolution circuits is shown to have a favorable training landscape, and numerical experiments demonstrate its relevance to simulating other many-body systems such as a Fermi-Hubbard model. For the SYK model in particular, we demonstrate the construction of a low-rank approximation that favors a shallower Trotterization. Finally, classical simulations of finite-N SYK models suggest that teleportation via a traversable wormhole instead of random unitary scrambling is achievable with O(20) qubits, providing further indication that such quantum gravity experiments may realizable with near-term quantum hardware.
", "doi": "10.7907/q75q-zm20", "publication_date": "2021", "thesis_type": "senior_major", "thesis_year": "2021" }, { "id": "thesis:11491", "collection": "thesis", "collection_id": "11491", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05022019-001421335", "type": "thesis", "title": "Searching for Gravitational Waves from Compact Binary Coalescences in Advanced LIGO Data", "author": [ { "family_name": "Sachdev", "given_name": "Surabhi", "orcid": "0000-0002-0525-2317", "clpid": "Sachdev-Surabhi" } ], "thesis_advisor": [ { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" } ], "thesis_committee": [ { "family_name": "Kasliwal", "given_name": "Mansi M.", "orcid": "0000-0002-5619-4938", "clpid": "Kasliwal-Mansi-M" }, { "family_name": "Reitze", "given_name": "David H.", "orcid": "0000-0002-5756-1111", "clpid": "Reitze-D-H" }, { "family_name": "Teukolsky", "given_name": "Saul A.", "orcid": "0000-0001-9765-4526", "clpid": "Teukolsky-S-A" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Advanced LIGO's first observing run marked the birth of gravitational-wave astronomy through the first detection of gravitational waves from coalescing black holes-GW150914. Advanced LIGO's second and Advanced Virgo's first observing run marked the birth of multimessenger astronomy with first joint observations of gravitational and electromagnetic radiation associated with coalescing neutron stars-GW170817. The electromagnetic observations included detection of a burst of gamma rays produced by the merger, and a kilonova powered by the radioactive decay of r-process nuclei synthesized in the neutron star coalescence ejecta. Gravitational waves from compact binary coalescences carry fingerprints of the sources that generated them. Studying them allows us to test Einstein\u2019s general relativity in the strongest regimes, where it has never been tested before, and study matter at densities beyond reach of the most powerful laboratories on our planet. Moreover, we can gain insight about the evolution of stars, galaxies and even the Universe as a whole by studying the merger rate of compact objects. Joint electromagnetic and gravitational-wave observations help develop our understanding of the physical processes that occur in such systems, and provide a new method of probing cosmological parameters.
\r\n\r\nGW170817 was detected by the GstLAL pipeline in low-latency making the extensive electromagnetic followup possible. The GstLAL pipeline is a matched filtering pipeline that uses compact binary coalescence waveform models to filter the data from gravitational-wave detectors in the time-domain. It can detect gravitational waves from coalescing compact binaries in near real time and provide point estimates for binary parameters. This thesis describes the methods, developments, and the results from the GstLAL pipeline over the course of the first two observing runs of Advanced LIGO, focusing on the contributions made by the author. We also present a study about the prospects of observing a cosmological stochastic background which is expected to be buried under the astrophysical background from the population of coalesceing compact binaries with third-generation gravitational-wave detectors.
", "doi": "10.7907/XNPA-PN03", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11576", "collection": "thesis", "collection_id": "11576", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302019-200300602", "type": "thesis", "title": "Light and Heat: Nonlocal Aspects in Conformal Field Theories", "author": [ { "family_name": "Kolo\u011flu", "given_name": "Murat", "orcid": "0000-0002-5082-8434", "clpid": "Kolo\u011flu-Murat" } ], "thesis_advisor": [ { "family_name": "Simmons-Duffin", "given_name": "David", "orcid": "0000-0002-2937-9515", "clpid": "Simmons-Duffin-D" } ], "thesis_committee": [ { "family_name": "Ooguri", "given_name": "Hirosi", "orcid": "0000-0001-6021-3778", "clpid": "Ooguri-H" }, { "family_name": "Simmons-Duffin", "given_name": "David", "orcid": "0000-0002-2937-9515", "clpid": "Simmons-Duffin-D" }, { "family_name": "Gukov", "given_name": "Sergei", "orcid": "0000-0002-9486-1762", "clpid": "Gukov-S" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis is dedicated to certain nonlocal aspects of conformal quantum field theories (CFTs). Two main directions are the study of CFTs on a particular globally-nontrivial spacetime corresponding to finite temperature, and the study of particular nonlocal CFT observables localized on light-rays. Specifically, we introduce bootstrap techniques for determining finite-temperature data of CFTs, and make novel predictions for the 2+1-dimensional Ising model. We propose the \u201cstringy equivalence principle\u201d, stating that coincident gravitational shocks commute, as a generalization of the strong equivalence principle of Einstein\u2019s General Relativity that must hold in all consistent theories of gravity. We prove it in Anti-de Sitter (AdS) spacetimes by studying light-ray operators in the holographically dual CFT. We also derive an operator product expansion (OPE) for light-ray operators in CFT, by which two light-ray operators on the same light-sheet can be expanded as a sum of single light-ray operators. Light-ray operators model detectors \u2014 such as calorimeters. We use the light-ray OPE to compute energy event shape observables suitable for conformal collider physics.
\r\n\r\nAn additional part of this thesis determines the low-energy vacua of two-dimensional maximal super-Yang-Mills theory, which describes the dynamics of stacks of D-strings in Type IIB string theory. By computing an invariant of the renormalization group (RG) flow from high to low energy \u2014 a modified thermal partition function named the refined elliptic genus \u2014 we prove the existence of multiple vacua, and identify the superconformal field theories capturing their dynamics. The vacua correspond to bound states of (p,q)-strings in Type IIB string theory. Our computation serves as a check of the strong-weak S-duality of the Type IIB string.
", "doi": "10.7907/DJ2W-AF45", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11019", "collection": "thesis", "collection_id": "11019", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06042018-162115007", "type": "thesis", "title": "The Effective Field Theory of Fermi Surfaces in the Vicinity of Van Hove Singularities", "author": [ { "family_name": "McKinney", "given_name": "Tristan James", "orcid": "0000-0003-2365-1810", "clpid": "McKinney-Tristan-James" } ], "thesis_advisor": [ { "family_name": "Kapustin", "given_name": "Anton N.", "orcid": "0000-0003-3903-5158", "clpid": "Kapustin-A" } ], "thesis_committee": [ { "family_name": "Kapustin", "given_name": "Anton N.", "orcid": "0000-0003-3903-5158", "clpid": "Kapustin-A" }, { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Motrunich", "given_name": "Olexei I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" } ], "local_group": [ { "literal": "Walter Burke Institute for Theoretical Physics" }, { "literal": "div_pma" } ], "abstract": "The use of effective field theories to attack new and seemingly disparate problems has proliferated in the past several decades. In this thesis, we develop effective field theories for systems of fermionic quasiparticles possessing Fermi surfaces, with a particular focus on Fermi surfaces proximal to Van Hove singularities. Such systems are a fruitful source of complex and novel behavior in condensed matter physics. We begin with an overview of the renormalization group procedure at the heart of effective field theory by analyzing a simple example. We emphasize the concept that the RG relates the observables of one theory to those of another theory with precisely the same form but different numerical parameters. We also note the generality and extensibility of these concepts. We then apply this perspective to the study of quasiparticles with a round Fermi surface, employing the technique of binning the quasiparticle fields in momentum space to translate previous treatments into a more modern form. We next develop an effective field theory describing the excitations of modes around a Fermi surface with a Van Hove singularity. We resolve lingering questions about the presence of nonlocal interactions in similar models. We find a rich and complicated theory capable of describing deviations from typical Fermi liquid behavior that nonetheless displays some universal dependence on the interactions involving modes in the vicinity of the Van Hove point. We close with an analysis of the instabilities of this Van Hove effective field theory.
", "doi": "10.7907/8VWF-V806", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10902", "collection": "thesis", "collection_id": "10902", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05162018-153827333", "primary_object_url": { "basename": "anderson_dustin_2018_thesis.pdf", "content": "final", "filesize": 18535499, "license": "other", "mime_type": "application/pdf", "url": "/10902/1/anderson_dustin_2018_thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Inclusive Searches for Supersymmetry at \u221as = 13 TeV Using Razor Kinematic Variables, and Data Scouting Using the CMS Trigger System", "author": [ { "family_name": "Anderson", "given_name": "Dustin James", "orcid": "0000-0001-8173-3182", "clpid": "Anderson-Dustin-James" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Cheung", "given_name": "Clifford W.", "orcid": "0000-0002-9983-9425", "clpid": "Cheung-Clifford" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "We present two searches for supersymmetric particles using proton-proton collision data collected by the CMS experiment at \u221as = 13 TeV. The searches use razor kinematic variables for signal discrimination and target the pair production of heavy gluinos and squarks in R-parity conserving supersymmetry. The first search is performed on 2.3 fb\u22121 of data collected by CMS in 2015. Two complete, independent background predictions are made: one based on fits using a parameterized functional form, and the other based on Monte Carlo simulation corrected via control samples in data. The second search is an expanded version of the first search, and is performed using the Monte Carlo-based background prediction method on 35.9 fb\u22121 of data collected in 2016. Both searches obtain results compatible with standard model background expectations. The null results are interpreted as limits on the masses and cross sections of gluinos, squarks, and higgsinos in the context of simplified models of supersymmetry. We discuss the outlook for the fit-based search strategy and explore how the technique of gaussian process regression may be useful as a tool to combat the challenges of this analysis methodology.
\r\n\r\nWe also describe a new paradigm for trigger-level collider data analysis, which we refer to as data scouting. In this paradigm, searches for new physics are performed using event information reconstructed within the experiment\u2019s trigger software. This circumvents traditional event rate constraints, such as disk space and the latency of offline reconstruction. We provide details on the implementation of a framework for data scouting in the CMS High-Level Trigger system and its successful use in Run II of the LHC. We discuss the impact of scouting on the physics program of CMS and demonstrate that it enables searches for new physics that would not otherwise be possible due to trigger constraints, such as hadronic resonance searches at low mass and searches for leptonic decays of dark photons.
", "doi": "10.7907/BHGN-VY70", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:11056", "collection": "thesis", "collection_id": "11056", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06082018-171453167", "type": "thesis", "title": "A Dark Matter Search Using the Final SuperCDMS Soudan Dataset and the Development of a Large-Format, Highly-Multiplexed, Athermal-Phonon-Mediated Particle Detector", "author": [ { "family_name": "Cornell", "given_name": "Brett Durcan", "clpid": "Cornell-Brett-Durcan" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Cheung", "given_name": "Clifford W.", "orcid": "0000-0002-9983-9425", "clpid": "Cheung-Clifford" }, { "family_name": "Schwab", "given_name": "Keith C.", "orcid": "0000-0001-8216-4815", "clpid": "Schwab-K-C" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Over the past eighty years, numerous complementary observations of our universe have indicated that our current description of physics is far from complete. The \"ordinary matter\", such as electrons, protons, photons and neutrons, that constitutes the bulk of all human physical experiences is actually only a minority (about 16%) of the total mass of the universe. The remaining 84% is very poorly understood, but has profound effects on the dynamics and evolution of our universe. Because it does not interact with light, and is not observable in telescopes on earth, this extra mass is usually referred to as \"dark matter\". Although the dark matter is poorly understood, Weakly Interacting Massive Particles (WIMPs) are a well-motivated candidate that can be directly detected via a non-gravitational interaction with normal matter, potentially allowing for direct terrestrial detection and characterization of this dark matter. This dissertation is focused on this direct WIMP detection and will be broken into two main parts.
\r\n\r\nThe first part focuses on the blinded analysis of roughly three years of data collected from March 2012 to November 2015 by the SuperCDMS Soudan experiment. SuperCDMS Soudan consists of an array of 15, 0.6-kg, cryogenic, Ge iZIP particle detectors situated in a decommissioned iron mine in remote northern Minnesota. This analysis is optimized to be sensitive to theoretical WIMP masses above 10 GeV/c2. This result set the strongest limits for WIMP--germanium-nucleus interactions for WIMP masses greater than 12 Gev/c2.
\r\n\r\nThe second part focuses on the development new kind of particle detector in the style of a SuperCDMS iZIP, designed to simplify fabrication and readout, improve phonon-based position reconstruction, and help to scale to larger target arrays. These detectors replace the TES-based phonon sensors of the iZIP with Microwave Kinetic Inductance Detectors (MKIDs).
", "doi": "10.7907/M297-J716", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:9896", "collection": "thesis", "collection_id": "9896", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07282016-144651775", "primary_object_url": { "basename": "Saberi_Ingmar_2016.pdf", "content": "final", "filesize": 1992686, "license": "other", "mime_type": "application/pdf", "url": "/9896/1/Saberi_Ingmar_2016.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Knots, Trees, and Fields: Common Ground Between Physics and Mathematics", "author": [ { "family_name": "Saberi", "given_name": "Ingmar Akira", "clpid": "Saberi-Ingmar-Akira" } ], "thesis_advisor": [ { "family_name": "Gukov", "given_name": "Sergei", "orcid": "0000-0002-9486-1762", "clpid": "Gukov-S" } ], "thesis_committee": [ { "family_name": "Gukov", "given_name": "Sergei", "orcid": "0000-0002-9486-1762", "clpid": "Gukov-S" }, { "family_name": "Schwarz", "given_name": "John H.", "orcid": "0000-0001-9861-7559", "clpid": "Schwarz-J-H" }, { "family_name": "Marcolli", "given_name": "Matilde", "orcid": "0000-0002-2045-2907", "clpid": "Marcolli-M" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "Caltech Theory" }, { "literal": "div_pma" } ], "abstract": "One main theme of this thesis is a connection between mathematical physics (in particular, the three-dimensional topological quantum field theory known as Chern-Simons theory) and three-dimensional topology. This connection arises because the partition function of Chern-Simons theory provides an invariant of three-manifolds, and the Wilson-loop observables in the theory define invariants of knots. In the first chapter, we review this connection, as well as more recent work that studies the classical limit of quantum Chern-Simons theory, leading to relations to another knot invariant known as the -polynomial. (Roughly speaking, this invariant can be thought of as the moduli space of flat connections on the knot complement.) In fact, the connection can be deepened: through an embedding into string theory, categorifications of polynomial knot invariants can be understood as spaces of BPS states.
\r\n\r\nWe go on to study these homological knot invariants, and interpret spectral sequences that relate them to one another in terms of perturbations of supersymmetric theories. Our point is more general than the application to knots; in general, when one perturbs any modulus of a supersymmetric theory and breaks a symmetry, one should expect a spectral sequence to relate the BPS states of the unperturbed and perturbed theories. We consider several diverse instances of this general lesson. In another chapter, we consider connections between supersymmetric quantum mechanics and the de Rham version of homotopy theory developed by Sullivan; this leads to a new interpretation of Sullivan's minimal models, and of Massey products as vacuum states which are entangled between different degrees of freedom in these models.
\r\n\r\nWe then turn to consider a discrete model of holography: a Gaussian lattice model defined on an infinite tree of uniform valence. Despite being discrete, the matching of bulk isometries and boundary conformal symmetries takes place as usual; the relevant group is , and all of the formulas developed for holography in the context of scalar fields on fixed backgrounds have natural analogues in this setting. The key observation underlying this generalization is that the geometry underlying AdS3/CFT2 can be understood algebraically, and the base field can therefore be changed while maintaining much of the structure. Finally, we give some analysis of -polynomials under change of base (to finite fields), bringing things full circle.
", "doi": "10.7907/Z9VX0DHZ", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10193", "collection": "thesis", "collection_id": "10193", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05222017-201555383", "primary_object_url": { "basename": "thesis_2017_EnricoHerrmann_final.pdf", "content": "final", "filesize": 2716844, "license": "other", "mime_type": "application/pdf", "url": "/10193/7/thesis_2017_EnricoHerrmann_final.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Scattering in N=4 Super Yang Mills and N=8 Supergravity", "author": [ { "family_name": "Herrmann", "given_name": "Enrico", "orcid": "0000-0002-3983-2993", "clpid": "Herrmann-Enrico" } ], "thesis_advisor": [ { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Trnka", "given_name": "Jaroslav", "clpid": "Trnka-Jaroslav" } ], "thesis_committee": [ { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Cheung", "given_name": "Clifford W.", "orcid": "0000-0002-9983-9425", "clpid": "Cheung-Clifford" }, { "family_name": "Trnka", "given_name": "Jaroslav", "clpid": "Trnka-Jaroslav" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "Caltech Theory" }, { "literal": "div_pma" } ], "abstract": "The scattering amplitudes of planar N = 4 super-Yang-Mills theory (sYM) exhibit a number of remarkable analytic structures, including dual conformal symmetry, logarithmic singularities of integrands, and the absence of poles at infinite loop momentum. None of these properties are apparent from our usual formulation of quantum field theory in terms of Lagrangians and Feynman rules. In the past years, the hidden features inspired a dual formulation for scattering amplitudes that is not built on the two pillars of locality and unitarity. Instead, a new geometric formulation in terms of Grassmannians and the amplituhedron emerged, which is based on the key analytic properties of scattering amplitudes in the planar sector of $\\N=4$ super-Yang-Mills theory. Starting from geometric concepts, the amplituhedron geometry derives all properties of scattering amplitudes in said theory, including locality and factorization. From a practical perspective, expanding the amplitude in terms of a local diagrams, the amplituhedron construction implies that scattering amplitudes in planar N=4 super-Yang-Mills are fully specified by a surprisingly simple subset of all unitarity cuts. Concretely, integrands are uniquely (up to an overall constant) fixed by demanding their vanishing on all spurious singularities.
\r\n\r\nExtending an initial proposal by Arkani-Hamed, Bourjaily, Cachazo, and Trnka, we conjecture that the same analytic structures extend beyond the planar limit of N=4 super-Yang-Mills. Furthermore we show that the $\\dlog$ and \\emph{no pole at infinity} constraints give the key integrand level analytic information contained in dual conformal symmetry in the planar sector. While it is presently unclear how to extend either dual conformal symmetry or the amplituhedron picture beyond the planar sector, our results suggest that related concepts might exist and await discovery.
\r\n\r\nIn order to support our conjectures, we have analyzed several nontrivial multi-loop multi-leg amplitudes. For the nonplanar three-loop four-point and two-loop five point $\\N = 4$ super-Yang-Mills amplitudes, we explicitly construct a complete basis of diagram integrands that has only logarithmic singularities and no poles at infinity. We also give examples at three loops showing how to make the logarithmic singularity properties manifest by writing explicit dlog forms. We give additional evidence at four and five loops supporting the nonplanar logarithmic singularity conjecture. Our investigations show that the singularity structures of planar and nonplanar integrands in N = 4 super-Yang-Mills are strikingly similar. Finally, we express the complete amplitude in terms of our special basis diagrams, with the coefficients determined by the vanishing conditions on the amplitude. By successfully carrying out this procedure, we provide nontrivial evidence that the \u201czero conditions\u201d also carry over into the nonplanar sector. Our analysis suggests that the concept of the amplituhedron can be extended to the nonplanar sector of N = 4 super-Yang-Mills theory and one might hope to ultimately reformulate more general quantum field theories in a geometric language.
\r\n\r\nUsing the marvelous squaring relation between Yang-Mills and gravity theories discovered by Bern, Carrasco, and Johansson (BCJ), we relate our newly gained knowledge on the Yang-Mills side to properties of gravity. We conjecture that to all loop orders, while N = 8 supergravity has poles at infinity, at least at four points it has only logarithmic singularities at finite locations. We provide nontrivial evidence for these conjectures. We describe the singularity structure of N = 8 supergravity at three loops and beyond.
\r\n\r\nIn order to approach a geometric formulation for scattering in gravitational theories, we retrace the initial steps taken in planar N=4 super-Yang-Mills in the gravitational setting. In particular, we study on-shell diagrams for gravity theories with any number of supersymmetries and find a compact Grassmannian formula in terms of edge variables of the graphs. Unlike in gauge theory where the analogous form involves only dlog-factors, in gravity we find a non-trivial numerator as well as higher degree poles in the edge variables. Based on the structure of the Grassmannian formula for $\\N=8$ supergravity we conjecture that gravity loop amplitudes also possess similar properties. In particular, we find that there are only logarithmic singularities on cuts with finite loop momentum and that poles at infinity are present.
", "doi": "10.7907/Z94J0C49", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10193", "collection": "thesis", "collection_id": "10193", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05222017-201555383", "primary_object_url": { "basename": "thesis_2017_EnricoHerrmann_final.pdf", "content": "final", "filesize": 2716844, "license": "other", "mime_type": "application/pdf", "url": "/10193/7/thesis_2017_EnricoHerrmann_final.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Scattering in N=4 Super Yang Mills and N=8 Supergravity", "author": [ { "family_name": "Herrmann", "given_name": "Enrico", "orcid": "0000-0002-3983-2993", "clpid": "Herrmann-Enrico" } ], "thesis_advisor": [ { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Trnka", "given_name": "Jaroslav", "clpid": "Trnka-Jaroslav" } ], "thesis_committee": [ { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Cheung", "given_name": "Clifford W.", "orcid": "0000-0002-9983-9425", "clpid": "Cheung-Clifford" }, { "family_name": "Trnka", "given_name": "Jaroslav", "clpid": "Trnka-Jaroslav" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "Caltech Theory" }, { "literal": "div_pma" } ], "abstract": "The scattering amplitudes of planar N = 4 super-Yang-Mills theory (sYM) exhibit a number of remarkable analytic structures, including dual conformal symmetry, logarithmic singularities of integrands, and the absence of poles at infinite loop momentum. None of these properties are apparent from our usual formulation of quantum field theory in terms of Lagrangians and Feynman rules. In the past years, the hidden features inspired a dual formulation for scattering amplitudes that is not built on the two pillars of locality and unitarity. Instead, a new geometric formulation in terms of Grassmannians and the amplituhedron emerged, which is based on the key analytic properties of scattering amplitudes in the planar sector of $\\N=4$ super-Yang-Mills theory. Starting from geometric concepts, the amplituhedron geometry derives all properties of scattering amplitudes in said theory, including locality and factorization. From a practical perspective, expanding the amplitude in terms of a local diagrams, the amplituhedron construction implies that scattering amplitudes in planar N=4 super-Yang-Mills are fully specified by a surprisingly simple subset of all unitarity cuts. Concretely, integrands are uniquely (up to an overall constant) fixed by demanding their vanishing on all spurious singularities.
\r\n\r\nExtending an initial proposal by Arkani-Hamed, Bourjaily, Cachazo, and Trnka, we conjecture that the same analytic structures extend beyond the planar limit of N=4 super-Yang-Mills. Furthermore we show that the $\\dlog$ and \\emph{no pole at infinity} constraints give the key integrand level analytic information contained in dual conformal symmetry in the planar sector. While it is presently unclear how to extend either dual conformal symmetry or the amplituhedron picture beyond the planar sector, our results suggest that related concepts might exist and await discovery.
\r\n\r\nIn order to support our conjectures, we have analyzed several nontrivial multi-loop multi-leg amplitudes. For the nonplanar three-loop four-point and two-loop five point $\\N = 4$ super-Yang-Mills amplitudes, we explicitly construct a complete basis of diagram integrands that has only logarithmic singularities and no poles at infinity. We also give examples at three loops showing how to make the logarithmic singularity properties manifest by writing explicit dlog forms. We give additional evidence at four and five loops supporting the nonplanar logarithmic singularity conjecture. Our investigations show that the singularity structures of planar and nonplanar integrands in N = 4 super-Yang-Mills are strikingly similar. Finally, we express the complete amplitude in terms of our special basis diagrams, with the coefficients determined by the vanishing conditions on the amplitude. By successfully carrying out this procedure, we provide nontrivial evidence that the \u201czero conditions\u201d also carry over into the nonplanar sector. Our analysis suggests that the concept of the amplituhedron can be extended to the nonplanar sector of N = 4 super-Yang-Mills theory and one might hope to ultimately reformulate more general quantum field theories in a geometric language.
\r\n\r\nUsing the marvelous squaring relation between Yang-Mills and gravity theories discovered by Bern, Carrasco, and Johansson (BCJ), we relate our newly gained knowledge on the Yang-Mills side to properties of gravity. We conjecture that to all loop orders, while N = 8 supergravity has poles at infinity, at least at four points it has only logarithmic singularities at finite locations. We provide nontrivial evidence for these conjectures. We describe the singularity structure of N = 8 supergravity at three loops and beyond.
\r\n\r\nIn order to approach a geometric formulation for scattering in gravitational theories, we retrace the initial steps taken in planar N=4 super-Yang-Mills in the gravitational setting. In particular, we study on-shell diagrams for gravity theories with any number of supersymmetries and find a compact Grassmannian formula in terms of edge variables of the graphs. Unlike in gauge theory where the analogous form involves only dlog-factors, in gravity we find a non-trivial numerator as well as higher degree poles in the edge variables. Based on the structure of the Grassmannian formula for $\\N=8$ supergravity we conjecture that gravity loop amplitudes also possess similar properties. In particular, we find that there are only logarithmic singularities on cuts with finite loop momentum and that poles at infinity are present.
", "doi": "10.7907/Z94J0C49", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:9904", "collection": "thesis", "collection_id": "9904", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08232016-112522351", "type": "thesis", "title": "Naturalness Confronts Nature: Searches for Supersymmetry with the CMS Detector in pp Collisions at \u221as = 8 and 13 TeV", "author": [ { "family_name": "Duarte", "given_name": "Javier Mauricio Gonzalez", "orcid": "0000-0002-5076-7096", "clpid": "Duarte-Javier-Mauricio-Gonzalez" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" }, { "family_name": "Newman", "given_name": "Harvey B.", "orcid": "0000-0003-0964-1480", "clpid": "Newman-H-B" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Schwarz", "given_name": "John H.", "orcid": "0000-0001-9861-7559", "clpid": "Schwarz-J-H" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "In this thesis, we present two inclusive searches for supersymmetric particles at 8 and 13 TeV using the razor variables and guided by the principle of naturalness. We build a framework to explore the natural supersymmetry parameter space of gluino and top squark masses and branching ratios, which is a unique attempt to cover this parameter space in a more complete way than ever before using LHC data. With this approach, the production of top squarks and gluinos are excluded below 700 GeV and 1.6 TeV, respectively, independent of the branching ratios, constituting one of the tightest constraints on natural supersymmetry from the LHC. Motivated by the need to mitigate the effects of multiple interactions per bunch crossing (pileup), an essential feature of present and future hadron colliders, in this thesis we also study the precision timing capabilities of a LYSO-based sampling calorimeter, and achieve a time resolution of 30 ps in electron test beam measurements. The achieved resolution corresponds to the precision needed to significantly reduce the inclusion of pileup particles in the reconstruction of the event of interest. This study is foundational in building an R and D program on precision timing for the high-luminosity LHC and other future hadron colliders. We also propose alternative simplified models to study Higgs-plus-jets events at the LHC, and reinterpret an excess observed at 8 TeV in the context of these models. Finally, we discuss a search for narrow resonances in the dijet mass spectrum at 13 TeV using the data-scouting technique at CMS, which records a smaller event format to increase the maximum recordable rate. For the benchmark models with a vector or axial-vector mediator that couples to quarks and dark matter particles, the dijet search excludes mediator masses from 0.5 TeV up to 2.7 TeV largely independent of the dark matter particle mass, which constitutes a larger exclusion than traditional mono-X searches at the LHC. In the plane of the dark matter-nucleon interaction cross section versus dark matter mass, the dijet search is also more sensitive than direct detection experiments for spin-dependent cross sections.", "doi": "10.7907/Z9GX48JV", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10189", "collection": "thesis", "collection_id": "10189", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05192017-195511866", "type": "thesis", "title": "Searches for New Physics at the Compact Muon Solenoid Experiment and Precision Timing Calorimetry", "author": [ { "family_name": "Pe\u00f1a", "given_name": "Cristi\u00e1n Herrera", "orcid": "0000-0002-4500-7930", "clpid": "Pe\u00f1a-Cristi\u00e1n-Herrera" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Schwarz", "given_name": "John H.", "orcid": "0000-0001-9861-7559", "clpid": "Schwarz-J-H" }, { "family_name": "Filippone", "given_name": "Bradley W.", "orcid": "0000-0002-2618-2688", "clpid": "Filippone-B-W" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "In this thesis, we present several searches for beyond the standard model physics in proton-proton collisions recorded by the Compact Muon Solenoid Experiment at center-of-mass energy of 8 and 13\\TeV. We search for particle dark matter in events with two or more jets and missing transverse momentum at $\\sqrt{s} = 8$ TeV, in this search we use the razor variables to discriminate signal from background events and thus improve the overall sensitivity of the analysis. We observe agreement between the observation and the background estimation. The interpretation of the results is carried out in the context of an effective field theory that couples the standard model quarks to the dark matter candidate. A search for anomalous production of Higgs bosons using 15.3 $\\mathrm{fb}^{-1}$ of proton-proton collisions at $\\sqrt{s} = 13$ TeV is also presented; this search selects events with a Higgs boson in association with jets, where the Higgs candidate decays into two photons. We also employ the razor variables ($\\mathrm{M_{R}}, \\mathrm{R}^{2}$) to discriminate signal from background. We observe an excess of events in one of the search bins with relatively high values of $\\mathrm{M_{R}}$ and $\\mathrm{R}^{2}$. The interpretation of this analysis is pair production of bottom squarks in the context of supersymmetry, this model is also presented in one of the appendices of this thesis. In the other appendix of this thesis, we present a search for new phenomena in high-mass diphoton events using 12.9 $\\mathrm{fb}^{-1}$ of proton-proton collisions at $\\sqrt{s} = 13$ TeV. This search observed a significant excess (3.4 standard deviations, local) with 2015 data at a diphoton invariant mass of 750 GeV, equivalent to $\\approx$ 20\\% of the current dataset. By repeating the search with the larger dataset collected in 2016, we found that the aforementioned excess has been greatly disfavored. Additionally, in order to confirm the robustness and correctness of the data analysis techniques used in this search, we have carried out a second -- completely independent -- analysis, which confirms the absence of an excess at a diphoton invariant mass of 750 GeV.
\r\n\r\nWe also present detector research and developments studies of electromagnetic calorimeters equipped with precision timing capabilities. We present several calorimeter prototypes that were tested at the Fermilab Test Beam Facility. These prototypes include LYSO-based calorimeters, tungsten-LYSO \"shashlik\" sampling calorimeters, micro-channel-plate sampling calorimeters, and silicon-based sampling calorimeters. The results of these studies indicate that time resolutions of the order of $\\sim$ 30 ps are readily available when measuring electromagnetic showers. A discussion about the applications of precision timing in high energy physics experiments is also presented, with a particular interest in pileup rejection in the context of the high-luminosity upgrade of the Large Hadron Collider foreseen to start in 2025.
", "doi": "10.7907/Z9MK69Z6", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:8958", "collection": "thesis", "collection_id": "8958", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012015-163200704", "primary_object_url": { "basename": "teply_grant_2015_thesis.pdf", "content": "final", "filesize": 15369733, "license": "other", "mime_type": "application/pdf", "url": "/8958/1/teply_grant_2015_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Measurement of the Polarization of the Cosmic Microwave Background with the BICEP2 and Keck Array Telescopes", "author": [ { "family_name": "Teply", "given_name": "Grant Paul", "clpid": "Teply-Grant-Paul" } ], "thesis_advisor": [ { "family_name": "Bock", "given_name": "James J.", "orcid": "0000-0002-5710-5212", "clpid": "Bock-J-J" } ], "thesis_committee": [ { "family_name": "Bock", "given_name": "James J.", "orcid": "0000-0002-5710-5212", "clpid": "Bock-J-J" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Dor\u00e9", "given_name": "Olivier P.", "orcid": "0000-0001-7432-2932", "clpid": "Dor\u00e9-O" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Precision polarimetry of the cosmic microwave background (CMB) has become a mainstay of observational cosmology. The \u039bCDM model predicts a polarization of the CMB at the level of a few \u03bcK, with a characteristic E-mode pattern. On small angular scales, a B-mode pattern arises from the gravitational lensing of E-mode power by the large scale structure of the universe. Inflationary gravitational waves (IGW) may be a source of B-mode power on large angular scales, and their relative contribution to primordial fluctuations is parameterized by a tensor-to-scalar ratio r. BICEP2 and Keck Array are a pair of CMB polarimeters at the South Pole designed and built for optimal sensitivity to the primordial B-mode peak around multipole l ~ 100. The BICEP2/Keck Array program intends to achieve a sensitivity to r \u2265 0.02. Auxiliary science goals include the study of gravitational lensing of E-mode into B-mode signal at medium angular scales and a high precision survey of Galactic polarization. These goals require low noise and tight control of systematics. We describe the design and calibration of the instrument. We also describe the analysis of the first three years of science data. BICEP2 observes a significant B-mode signal at 150 GHz in excess of the level predicted by the lensed-\u039bCDM model, and Keck Array confirms the excess signal at > 5\u03c3. We combine the maps from the two experiments to produce 150 GHz Q and U maps which have a depth of 57 nK deg (3.4 \u03bcK arcmin) over an effective area of 400 deg2 for an equivalent survey weight of 248000 \u03bcK2. We also show preliminary Keck Array 95 GHz maps. A joint analysis with the Planck collaboration reveals that much of BICEP2/Keck Array's observed 150 GHz signal at low l is more likely a Galactic dust foreground than a measurement of r. Marginalizing over dust and r, lensing B-modes are detected at 7.0\u03c3 significance.", "doi": "10.7907/Z9XP72WM", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8733", "collection": "thesis", "collection_id": "8733", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12012014-145657884", "primary_object_url": { "basename": "YiChen-Thesis-20141201.pdf", "content": "final", "filesize": 8917676, "license": "other", "mime_type": "application/pdf", "url": "/8733/1/YiChen-Thesis-20141201.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Extraction of CP Properties of the H(125) Boson Discovered in Proton-Proton Collisions at sqrt(s) = 7 and 8 TeV with the CMS Detector at the LHC", "author": [ { "family_name": "Chen", "given_name": "Yi", "clpid": "Chen-Yi" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" }, { "family_name": "Newman", "given_name": "Harvey B.", "orcid": "0000-0003-0964-1480", "clpid": "Newman-H-B" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "In this thesis we build a novel analysis framework to perform the direct extraction of all possible effective Higgs boson couplings to the neutral electroweak gauge bosons in the H \u2192 ZZ(*) \u2192 4l channel also referred to as the golden channel. We use analytic expressions of the full decay differential cross sections for the H \u2192 VV' \u2192 4l process, and the dominant irreducible standard model qq \u0304 \u2192 4l background where 4l = 2e2\u03bc,4e,4\u03bc. Detector effects are included through an explicit convolution of these analytic expressions with transfer functions that model the detector responses as well as acceptance and efficiency effects. Using the full set of decay observables, we construct an unbinned 8-dimensional detector level likelihood function which is con- tinuous in the effective couplings, and includes systematics. All potential anomalous couplings of HVV' where V = Z,\u03b3 are considered, allowing for general CP even/odd admixtures and any possible phases. We measure the CP-odd mixing between the tree-level HZZ coupling and higher order CP-odd couplings to be compatible with zero, and in the range [\u22120.40, 0.43], and the mixing between HZZ tree-level coupling and higher order CP -even coupling to be in the ranges [\u22120.66, \u22120.57] \u222a [\u22120.15, 1.00]; namely compatible with a standard model Higgs. We discuss the expected precision in determining the various HVV' couplings in future LHC runs. A powerful and at first glance surprising prediction of the analysis is that with 100-400 fb-1, the golden channel will be able to start probing the couplings of the Higgs boson to diphotons in the 4l channel. We discuss the implications and further optimization of the methods for the next LHC runs.", "doi": "10.7907/VT37-HT20", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8845", "collection": "thesis", "collection_id": "8845", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05052015-155442785", "primary_object_url": { "basename": "AMott_PhDThesis_SubmissionVersion1.pdf", "content": "final", "filesize": 8508296, "license": "other", "mime_type": "application/pdf", "url": "/8845/1/AMott_PhDThesis_SubmissionVersion1.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Search for Higgs Boson Production Beyond the Standard Model Using the Razor Kinematic Variables in pp Collisions at \u221as=8 TeV and Optimization of Higgs Boson Identification Using a Quantum Annealer", "author": [ { "family_name": "Mott", "given_name": "Alexander Robert", "clpid": "Mott-Alexander-Robert" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Spiropulu", "given_name": "Maria", "clpid": "Spiropulu-M" }, { "family_name": "Newman", "given_name": "Harvey B.", "clpid": "Newman-H-B" }, { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" }, { "family_name": "Schwarz", "given_name": "John H.", "clpid": "Schwarz-J-H" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "In the first part of this thesis we search for beyond the Standard Model physics through the search for anomalous production of the Higgs boson using the razor kinematic variables. We search for anomalous Higgs boson production using proton-proton collisions at center of mass energy \u221as=8 TeV collected by the Compact Muon Solenoid experiment at the Large Hadron Collider corresponding to an integrated luminosity of 19.8 fb-1.
\r\n\r\nIn the second part we present a novel method for using a quantum annealer to train a classifier to recognize events containing a Higgs boson decaying to two photons. We train that classifier using simulated proton-proton collisions at \u221as=8 TeV producing either a Standard Model Higgs boson decaying to two photons or a non-resonant Standard Model process that produces a two photon final state.
\r\n\r\nThe production mechanisms of the Higgs boson are precisely predicted by the Standard Model based on its association with the mechanism of electroweak symmetry breaking. We measure the yield of Higgs bosons decaying to two photons in kinematic regions predicted to have very little contribution from a Standard Model Higgs boson and search for an excess of events, which would be evidence of either non-standard production or non-standard properties of the Higgs boson. We divide the events into disjoint categories based on kinematic properties and the presence of additional b-quarks produced in the collisions. In each of these disjoint categories, we use the razor kinematic variables to characterize events with topological configurations incompatible with typical configurations found from standard model production of the Higgs boson.
\r\n\r\nWe observe an excess of events with di-photon invariant mass compatible with the Higgs boson mass and localized in a small region of the razor plane. We observe 5 events with a predicted background of 0.54 ± 0.28, which observation has a p-value of 10-3 and a local significance of 3.35σ. This background prediction comes from 0.48 predicted non-resonant background events and 0.07 predicted SM higgs boson events. We proceed to investigate the properties of this excess, finding that it provides a very compelling peak in the di-photon invariant mass distribution and is physically separated in the razor plane from predicted background. Using another method of measuring the background and significance of the excess, we find a 2.5σ deviation from the Standard Model hypothesis over a broader range of the razor plane.
\r\n\r\nIn the second part of the thesis we transform the problem of training a classifier to distinguish events with a Higgs boson decaying to two photons from events with other sources of photon pairs into the Hamiltonian of a spin system, the ground state of which is the best classifier. We then use a quantum annealer to find the ground state of this Hamiltonian and train the classifier. We find that we are able to do this successfully in less than 400 annealing runs for a problem of median difficulty at the largest problem size considered. The networks trained in this manner exhibit good classification performance, competitive with the more complicated machine learning techniques, and are highly resistant to overtraining. We also find that the nature of the training gives access to additional solutions that can be used to improve the classification performance by up to 1.2% in some regions.
", "doi": "10.7907/Z9XK8CHR", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:7671", "collection": "thesis", "collection_id": "7671", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05072013-174540453", "primary_object_url": { "basename": "Rogan_THESIS_final.pdf", "content": "final", "filesize": 27234270, "license": "other", "mime_type": "application/pdf", "url": "/7671/1/Rogan_THESIS_final.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Searches for New Symmetries in pp Collisions with the Razor Kinematic Variables at \u221as = 7 TeV", "author": [ { "family_name": "Rogan", "given_name": "Christopher Sean", "clpid": "Rogan-Christopher-Sean" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Spiropulu", "given_name": "Maria", "clpid": "Spiropulu-M" }, { "family_name": "Newman", "given_name": "Harvey B.", "clpid": "Newman-H-B" }, { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" }, { "family_name": "Schwarz", "given_name": "John H.", "clpid": "Schwarz-J-H" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "The construction and LHC phenomenology of the razor variables MR, an event-by-event indicator of the heavy particle mass scale, and R, a dimensionless variable related to the transverse momentum imbalance of events and missing transverse energy, are presented. \u00a0The variables are used \u00a0in the analysis of the first proton-proton collisions dataset at CMS \u00a0(35 pb-1) in a search for superpartners of the quarks and gluons, targeting indirect hints of dark matter candidates in the context of supersymmetric theoretical frameworks. The analysis produced the highest sensitivity results for SUSY to date and extended the LHC reach far beyond the previous Tevatron results. \u00a0A generalized inclusive search is subsequently presented for new heavy particle pairs produced in \u221as = 7 TeV proton-proton collisions at the LHC using 4.7\u00b10.1 fb-1 of integrated luminosity from the second LHC run of 2011. \u00a0The selected events are analyzed in the 2D razor-space of MR and R and the analysis is performed in 12 tiers of all-hadronic, single and double leptons\u00a0final states in the presence and absence of b-quarks, probing the third generation sector using the event heavy-flavor content. \u00a0 The search is sensitive to generic supersymmetry models with minimal assumptions about the superpartner decay chains. No excess is observed in the number or shape of event yields relative to Standard Model predictions. Exclusion limits are derived in the CMSSM framework with \u00a0gluino masses up to 800 GeV and squark masses up to 1.35 TeV excluded at 95% confidence level, depending on the model parameters. The results are also interpreted for a collection of simplified models, in which gluinos are excluded with masses as large as 1.1 TeV, for small neutralino masses, and the first-two generation squarks, stops and sbottoms are excluded for masses up to about 800, 425 and 400 GeV, respectively.
\r\n\r\nWith the discovery of a new boson by the CMS and ATLAS experiments in the \u03b3-\u03b3 and 4 lepton final states, the identity of the putative Higgs candidate must be established through the measurements of its properties. The spin and quantum numbers are of particular importance, and we describe a method for measuring the JPC of this particle using the observed signal events in the H to ZZ* to 4 lepton channel developed before the discovery. Adaptations of the razor kinematic variables are introduced for the H to WW* to 2 lepton/2 neutrino channel, improving the resonance mass resolution and increasing the discovery significance. The prospects for incorporating this channel in an examination of the new boson JPC is discussed, with indications that this it could provide complementary information to the H to ZZ* to 4 lepton final state, particularly for measuring CP-violation in these decays.
", "doi": "10.7907/B0MD-F026", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7770", "collection": "thesis", "collection_id": "7770", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302013-043445308", "type": "thesis", "title": "Studies of Z\u03b3 Production and Constraints on Anomalous Triple Gauge Couplings in pp Collisions at \u221as = 7 TeV", "author": [ { "family_name": "Veverka", "given_name": "Jan", "clpid": "Veverka-Jan" } ], "thesis_advisor": [ { "family_name": "Newman", "given_name": "Harvey B.", "orcid": "0000-0003-0964-1480", "clpid": "Newman-H-B" } ], "thesis_committee": [ { "family_name": "Newman", "given_name": "Harvey B.", "orcid": "0000-0003-0964-1480", "clpid": "Newman-H-B" }, { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Patterson", "given_name": "Ryan B.", "orcid": "0000-0002-5787-9517", "clpid": "Patterson-R-B" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "In this thesis, we test the electroweak sector of the Standard Model of particle physics through the measurements of the cross section of the simultaneous production of the neutral weak boson Z and photon γ, and the limits on the anomalous Zγγ and ZZγ triple gauge couplings h3 and h4 with the Z decaying to leptons (electrons and muons). We analyze events collected in proton-proton collisions at center of mass energy of sqrt(s) = 7 TeV corresponding to an integrated luminosity of 5.0 inverse femtobarn. The analyzed events were recorded by the Compact Muon Solenoid detector at the Large Hadron Collider in 2011.
\r\n\r\nThe production cross section has been measured for hard photons with transverse momentum greater than 15 GeV that are separated from the the final state leptons in the eta-phi plane by Delta R greater than 0.7, whose sum of the transverse energy of hadrons over the transverse energy of the photon in a cone around the photon with Delta R less than 0.3 is less than 0.5, and with the invariant mass of the dilepton system greater than 50 GeV. The measured cross section value is 5.33 +/- 0.08 (stat.) +/- 0.25 (syst.) +/- 0.12 (lumi.) picobarn. This is compatible with the Standard Model prediction that includes next-to-leading-order QCD contributions: 5.45 +/- 0.27 picobarn.
\r\n\r\nThe measured 95 % confidence-level upper limits on the absolute values of the anomalous couplings h3 and h4 are 0.01 and 8.8E-5 for the Zγγ interactions, and, 8.6E-3 and 8.0E-5 for the ZZγ interactions. These values are also compatible with the Standard Model where they vanish in the tree-level approximation. They extend the sensitivity of the 2012 results from the ATLAS collaboration based on 1.02 inverse femtobarn of data by a factor of 2.4 to 3.1.
\r\n", "doi": "10.7907/QTWD-J259", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7103", "collection": "thesis", "collection_id": "7103", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302012-170816705", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 1380121, "license": "other", "mime_type": "application/pdf", "url": "/7103/1/thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "4d/2d Correspondence: Instantons and W-Algebras", "author": [ { "family_name": "Song", "given_name": "Jaewon", "orcid": "0000-0002-1238-2435", "clpid": "Song-Jaewon" } ], "thesis_advisor": [ { "family_name": "Ooguri", "given_name": "Hirosi", "orcid": "0000-0001-6021-3778", "clpid": "Ooguri-H" } ], "thesis_committee": [ { "family_name": "Ooguri", "given_name": "Hirosi", "orcid": "0000-0001-6021-3778", "clpid": "Ooguri-H" }, { "family_name": "Schwarz", "given_name": "John H.", "orcid": "0000-0001-9861-7559", "clpid": "Schwarz-J-H" }, { "family_name": "Kapustin", "given_name": "Anton N.", "orcid": "0000-0003-3903-5158", "clpid": "Kapustin-A" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "Caltech Theory" }, { "literal": "div_pma" } ], "abstract": "In this thesis, we study the 4d/2d correspondence of Alday-Gaiotto-Tachikawa, which relates the class of 4-dimensional N=2 gauge theories (theories of class S) to a 2-dimensional conformal field theory. The 4d gauge theories are obtained by compactifying 6-dimensional N=(2, 0) theory of type A, D, E on a Riemann surface C. On the 2-dimensional side, we have Toda theory on the surface C with W-algebra symmetry, which is an extension of the Virasoro symmetry. In particular, the instanton partition function of the 4d gauge theory is reproduced by a conformal/chiral block of Virasoro/W-algebra. We develop techniques to compute the partition functions on 4d and 2d sides, for various gauge groups and matter fields.
\r\n\r\nWe generalize the Alday-Gaiotto-Tachikawa 4d/2d correspondence to various cases. First, we study N=2 pure Yang-Mills theory with arbitrary gauge groups, including the exceptional groups. We explicitly construct the corresponding W-algebra currents, and confirm the correspondence holds at 1-instanton level. Second, we study the conformal quiver theory with Sp(1)-SO(4) gauge group. Finally, we study Sicilian gauge theories with trifundamental half-hypermultiplets. We also find that the conformal theories with Sp(1) gauge group and SU(2) gauge group have different instanton partition functions in terms of bare gauge couplings. We show this is an artifact of the renormalization scheme, by explicitly constructing a map between the bare couplings and studying its geometrical interpretations. This demonstrates the scheme independence of renormalization at the non-perturbative level.
", "doi": "10.7907/WP20-DX98", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6189", "collection": "thesis", "collection_id": "6189", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11242010-093045913", "type": "thesis", "title": "The Charged Particle Multiplicity at Center of Mass Energies from 900 GeV to 7 TeV Measured with the ATLAS Experiment at the Large Hadron Collider\r ", "author": [ { "family_name": "Gray", "given_name": "Heather Mary", "clpid": "Gray-Heather-Mary" } ], "thesis_advisor": [ { "family_name": "Hughes", "given_name": "Emlyn Willard", "clpid": "Hughes-Emlyn-Willard" } ], "thesis_committee": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Wise", "given_name": "Mark B.", "clpid": "Wise-M-B" }, { "family_name": "Spiropulu", "given_name": "Maria", "clpid": "Spiropulu-M" }, { "family_name": "Hughes", "given_name": "Emlyn Willard", "clpid": "Hughes-Emlyn-Willard" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "The first measurements made by the ATLAS experiment at the LHC are presented. The charged particle multiplicity, its dependence on transverse momentum and pseudorapidity, and the relationship between mean transverse momentum and pseudorapidity are measured for events with at least one charged particle in the kinematic range |\u03b7| < 2.5 and pT > 500 MeV. The charged particle multiplicity distributions are measured at the three centre of mass energies at which protons have been collided in the LHC: 900 GeV, 2.36 TeV and 7 TeV. The results are compared to predictions from Monte Carlo models of proton-proton collisions. All models predicted a multiplicity at least 10% lower than was measured. They also failed to predict a sufficient increase in the multiplicity when the centre of mass energy increased from 900 GeV to 7 TeV. Updated models have already been produced using these data, which provide a significantly better description of the properties of proton-proton collisions at LHC energies.", "doi": "10.7907/VVAE-6186", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:6221", "collection": "thesis", "collection_id": "6221", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12292010-171553189", "primary_object_url": { "basename": "ThesisMain_D.pdf", "content": "final", "filesize": 5064130, "license": "other", "mime_type": "application/pdf", "url": "/6221/1/ThesisMain_D.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "A Measurement of Jet Shapes in Proton-Proton Collisions at 7.0 TeV Center-of-Mass Energy with the ATLAS Detector at the Large Hadron Collider", "author": [ { "family_name": "Marshall", "given_name": "Zachary Louis", "clpid": "Marshall-Zachary-Louis" } ], "thesis_advisor": [ { "family_name": "Hughes", "given_name": "Emlyn Willard", "clpid": "Hughes-Emlyn-Willard" } ], "thesis_committee": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Politzer", "given_name": "Hugh David", "clpid": "Politzer-H-D" }, { "family_name": "Hughes", "given_name": "Emlyn Willard", "clpid": "Hughes-Emlyn-Willard" }, { "family_name": "Spiropulu", "given_name": "Maria", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "A study of jet shapes is presented using 300 nb\u22121 of proton-proton collision data collected at a center of mass energy of 7 TeV using the ATLAS detector at the Large Hadron Collider. The analysis includes jets with rapidity |y| < 2.8 and with calibrated transverse momentum 40 < pT < 600 GeV. Results are compared with several tuned Monte Carlo programs. Jets are found to be wider than predicted, although the evolution of the jet shape with transverse momentum is well described.", "doi": "10.7907/0JS1-ZY30", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" } ]