CaltechAUTHORS: Combined
https://feeds.library.caltech.edu/people/Wise-M-B/combined.rss
A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenThu, 07 Nov 2024 19:31:14 -0800Radiative weak decays of baryons as single-quark transitions
https://resolver.caltech.edu/CaltechAUTHORS:GILprd79a
Year: 1979
DOI: 10.1103/PhysRevD.19.976
Radiative weak decays are investigated in the context of the quark model assuming the basic transition is an s quark decaying to a d quark plus a photon. This assumption, which encompasses a number of more detailed models, is used to predict relative rates and angular distributions for radiative weak decays of baryons. The measured decay rate for Σ+→pγ and upper limit on that for Ξ-→Σ-γ are in disagreement with the predictions and appear to rule out such models.https://resolver.caltech.edu/CaltechAUTHORS:GILprd79aDiagrammatic analysis of some contributions to the ΔI = 1/2 rule
https://resolver.caltech.edu/CaltechAUTHORS:20120727-113853665
Year: 1979
DOI: 10.1103/PhysRevD.20.1216
Higher-order gluon corrections to a particular mechanism for the ΔI=1/2 rule are computed using quantum chromodynamics. It is found that due to gauge invariance these corrections leave the form of the lowest-order result essentially unchangedhttps://resolver.caltech.edu/CaltechAUTHORS:20120727-113853665Effective Hamiltonian for ΔS=1 weak nonleptonic decays in the six-quark model
https://resolver.caltech.edu/CaltechAUTHORS:GILprd79b
Year: 1979
DOI: 10.1103/PhysRevD.20.2392
Strong-interaction corrections to the nonleptonic weak-interaction Hamiltonian are calculated in the leading-logarithmic approximation using quantum chromodynamics. Starting with a six-quark theory, the W boson, t quark, b quark, and c quark are successively considered as "heavy" and the effective Hamiltonian calculated. The resulting effective Hamiltonian for strangeness-changing nonleptonic decays involves u, d, and s quarks and has possible CP-violating pieces both in the usual (V-A)×(V-A) terms and in induced, "penguin"-type terms. Numerically, the CP-violating compared to CP-conserving parts of the latter terms are close to results calculated on the basis of the lowest-order "penguin" diagram.https://resolver.caltech.edu/CaltechAUTHORS:GILprd79bCabibbo-suppressed nonleptonic D decays
https://resolver.caltech.edu/CaltechAUTHORS:ABBprd80a
Year: 1980
DOI: 10.1103/PhysRevD.21.768
We discuss why an extension of the ideas used to explain the ΔI=1/2 rule in kaon and hyperon decays does not lead to an analogous large enhancement in the rates of Cabibbo-suppressed nonleptonic D-meson decays. The possibility of seeing the contribution of diagrams with a virtual b-quark loop through interference effects is also discussed.https://resolver.caltech.edu/CaltechAUTHORS:ABBprd80aConstraints on charged-Higgs-boson couplings
https://resolver.caltech.edu/CaltechAUTHORS:ABBprd80
Year: 1980
DOI: 10.1103/PhysRevD.21.1393
Using the experimental value of the KL-KS mass difference, the authors derive constraints on charged-Higgs-boson couplings in gauge theories of the weak and electromagnetic interactions. These bounds severely restrict the possible magnitude of charged-Higgs-boson effects in K and D meson decays. The results are based on the observation that charged-Higgs-boson-exchange contributions to K0-K0 mixing are of order 1/MH^2 whereas the corresponding W-boson contribution is only of order mc^2/MW^4.https://resolver.caltech.edu/CaltechAUTHORS:ABBprd80K→πe+e- in the six-quark model
https://resolver.caltech.edu/CaltechAUTHORS:GILprd80
Year: 1980
DOI: 10.1103/PhysRevD.21.3150
The decay K→πe+e- is considered in the six-quark model. The effective Hamiltonian applicable to such decays is calculated in leading-logarithmic approximation and attention is focused on the magnitude of CP-violating effects.https://resolver.caltech.edu/CaltechAUTHORS:GILprd80Effective Hamiltonian for nucleon decay
https://resolver.caltech.edu/CaltechAUTHORS:ABBprd80c
Year: 1980
DOI: 10.1103/PhysRevD.22.2208
Renormalization effects for the SU(3) ⊗ SU(2) ⊗ U(1)-invariant baryon-number-violating operators of lowest dimension are calculated. Linear relations involving these operators are presented and a minimal set is given for nucleon decay processes.https://resolver.caltech.edu/CaltechAUTHORS:ABBprd80cThree-body decays of the proton
https://resolver.caltech.edu/CaltechAUTHORS:WISprd81a
Year: 1981
DOI: 10.1103/PhysRevD.23.1591
The rates for the three-body proton decays p→ππe+ are related to the rate for the decay p→π0e+. This is done by making an ansatz for the form of the three-body amplitude which is consistent with current algebra and with the measured ππ final-state interactions. We find that the three-body decay rates are comparable with the rate for the two-body decay p→π0e+.https://resolver.caltech.edu/CaltechAUTHORS:WISprd81aSU(5) and the Invisible Axion
https://resolver.caltech.edu/CaltechAUTHORS:WISprl81a
Year: 1981
DOI: 10.1103/PhysRevLett.47.402
Dine, Fischler, and Srednicki have proposed a solution to the strong CP puzzle in which the mass and couplings of the axion are suppressed by an inverse power of a large mass. We construct an explicit SU(5) model in which this mass is the vacuum expectation value which breaks SU(5) down to SU(3) ⊗ SU(2) ⊗ U(1).https://resolver.caltech.edu/CaltechAUTHORS:WISprl81aIsospin violation in J / ψ→baryon + antibaryon
https://resolver.caltech.edu/CaltechAUTHORS:CLAprd82
Year: 1982
DOI: 10.1103/PhysRevD.25.1345
Isospin-violating electromagnetic contributions to the decays J / ψ→baryon+antibaryon are examined. We find that these isospin-violating effects may be large, and that they depend sensitively on the magnetic form factors of the baryons.https://resolver.caltech.edu/CaltechAUTHORS:CLAprd82K0-K(bar)0 mixing in the six-quark model
https://resolver.caltech.edu/CaltechAUTHORS:GILprd83
Year: 1983
DOI: 10.1103/PhysRevD.27.1128
Using the leading-logarithm approximation, strong-interaction corrections to K0-K(bar)0 mixing in the six-quark model are computed in quantum chromodynamics. The full calculation involving the mixing of eight operators at some stages is done, as well as an approximate, much simpler calculation. Numerically, the exact and approximate results agree to high accuracy and both show that the corrections to the real and imaginary parts can be large. How to obtain the free-quark limit of these and other results is shown explicitly.https://resolver.caltech.edu/CaltechAUTHORS:GILprd83Top-Quark Mass and Bottom-Quark Decay
https://resolver.caltech.edu/CaltechAUTHORS:20120713-105243890
Year: 1983
The possibility of a long B-meson lifetime is explored, in which case the weak mixing angles θ_2 and θ_3 are quite small. This allows the derivation of a lower bound on the top-quark mass as a function of the B-meson lifetime, by comparison of the short-distance prediction for the CP-nonconservation parameter ε with its experimental value. The bound is significant for τ_B>4×10^(-13) s.https://resolver.caltech.edu/CaltechAUTHORS:20120713-105243890Relations between spatial correlations of rich clusters of galaxies
https://resolver.caltech.edu/CaltechAUTHORS:20161005-151454504
Year: 1984
The authors express the N-point rich cluster correlation function in terms of the two-point rich cluster correlation function in a model where rich clusters formed wherever suitably averaged primordial energy density fluctuations are unusually large. The validity of the results is not restricted to regions where the connected (reduced) N-point correlation functions are small compared with unity.https://resolver.caltech.edu/CaltechAUTHORS:20161005-151454504Validity of Chiral Perturbation Theory for K0-K―0 Mixing
https://resolver.caltech.edu/CaltechAUTHORS:BIJprl84
Year: 1984
DOI: 10.1103/PhysRevLett.53.2367
Chiral perturbation theory relates the |ΔS|=2 matrix element 〈K―0|(s―d)V-A×(s―d)V-A|K0〉 to the |ΔS|=1 matrix element 〈π+π0|(s―d)V-A(u―u)V-A+(s―u)V-A×(u―d)V-A-(s―d)V-A(d―d)V-A|K+〉. The latter matrix element is measured in K+→π+π0 decay and the former matrix element is relevant for the predictions that the standard model makes for CP nonconservation in K0-K―0 mixing. In this paper the corrections of order mK4 lnmK2 to lowest-order chiral perturbation theory (i.e., order mK2) for these matrix elements are computed. The correction is large for the |ΔS|=2 matrix element indicating a breakdown of chiral perturbation theory.https://resolver.caltech.edu/CaltechAUTHORS:BIJprl84Application of chiral perturbation theory to K→2π decays
https://resolver.caltech.edu/CaltechAUTHORS:BERprd85
Year: 1985
DOI: 10.1103/PhysRevD.32.2343
Chiral perturbation theory is applied to the decay K→2π. It is shown that, to quadratic order in meson masses, the amplitude for K→2π can be written in terms of the unphysical amplitudes K→π and K→0, where 0 is the vacuum. One may then hope to calculate these two simpler amplitudes with lattice Monte Carlo techniques, and thereby gain understanding of the ΔI=1/2 rule in K decay. The reason for the presence of the K→0 amplitude is explained: it serves to cancel off unwanted renormalization contributions to K→π. We make a rough test of the practicability of these ideas in Monte Carlo studies. We also describe a method for evaluating meson decay constants which does not require a determination of the quark masses.https://resolver.caltech.edu/CaltechAUTHORS:BERprd85Two-Point Correlation for Rich Clusters of Galaxies
https://resolver.caltech.edu/CaltechAUTHORS:20161005-152736636
Year: 1986
DOI: 10.1103/PhysRevLett.56.1878
The rich-cluster two-point correlation function is examined in a model where rich clusters of galaxies form at high peaks of primordial Gaussian mass-density fluctuations (averaged over a suitable volume). Particular attention is paid to the case when the primordial fluctuations have a Zel'dovich spectrum.https://resolver.caltech.edu/CaltechAUTHORS:20161005-152736636The significance of voids
https://resolver.caltech.edu/CaltechAUTHORS:20161005-151942807
Year: 1986
DOI: 10.1086/164144
The statistical significance of voids in the spatial distribution of galaxies or clusters of galaxies is studied. The probability per unit volume of finding a large void is expressed in terms of correlation functions. Numerical simulations are used to estimate the likelihood of observing a large void in the distribution of rich clusters of galaxies, assuming that rich clusters arose wherever suitably averaged primordial density fluctuations were unusually large.https://resolver.caltech.edu/CaltechAUTHORS:20161005-151942807Interpretation of large-scale deviations from the Hubble flow
https://resolver.caltech.edu/CaltechAUTHORS:20161005-153314099
Year: 1987
DOI: 10.1086/165076
The theoretical expectation for large-scale streaming velocities relative to the Hubble flow is expressed in terms of statistical correlation functions. Only for objects that trace the mass would these velocities have a simple cosmological interpretation. If some biasing effects the objects' formation, then nonlinear gravitational evolution is essential to predicting the expected large-scale velocities, which also depend on the nature of the biasing.https://resolver.caltech.edu/CaltechAUTHORS:20161005-153314099Correlations of peaks of Gaussian random fields
https://resolver.caltech.edu/CaltechAUTHORS:20160915-090959065
Year: 1987
DOI: 10.1007/BF01217812
The high peaks of a Gaussian random field are studied. Asymptotic expansions, appropriate for high peak thresholds and large spatial separations, are developed for the N-point correlation functions of the number density of high peaks, in terms of the two-point correlation of the underlying Gaussian field. Similar expressions are derived for the correlations of points, not necessarily the positions of peaks, where the field exceeds a high threshold.https://resolver.caltech.edu/CaltechAUTHORS:20160915-090959065Non-Gaussian Fluctuations
https://resolver.caltech.edu/CaltechAUTHORS:20200928-152422345
Year: 1988
DOI: 10.1007/978-94-009-4015-4_6
Natural primordial mass density fluctuations are those for which the probability distribution, for the mass density fluctuations averaged over the horizon volume, is independent of time. This criterion determines the two-point correlation of the mass density fluctuations to have a Zeldovich power spectrum but allows for many types of higher correlations. If the connected higher correlations vanish the primordial fluctuations are Gaussian. In this case the probability distribution develops into a non-Gaussian one due to the non-linear time evolution. The nature of this non- Gaussian distribution and its effects on the large scale distribution of galaxies or clusters of galaxies and their large scale streaming velocities is explored. Next the possibility of natural primordial non-Gaussian fluctuations is examined. These can give rise to a very different large scale distribution of galaxies (or clusters of galaxies) than the Gaussian primordial fluctuations.https://resolver.caltech.edu/CaltechAUTHORS:20200928-152422345Universality of Random-Matrix Predictions for the Statistics of Energy Levels
https://resolver.caltech.edu/CaltechAUTHORS:KAMprl88
Year: 1988
DOI: 10.1103/PhysRevLett.60.1995
Wigner statistics for correlations of matrix eigenvalues are shown to be a property of any matrix ensemble with a density of levels and probability distributions for matrix elements that are smooth. This justifies the universality of level correlations in generic quantum systems, while suggesting that level widths and other eigenvector-dependent statistics are system dependent.https://resolver.caltech.edu/CaltechAUTHORS:KAMprl88Leading logarithms of heavy quark masses in processes with light and heavy quarks
https://resolver.caltech.edu/CaltechAUTHORS:20161018-091807641
Year: 1988
DOI: 10.1016/0370-2693(88)90718-6
The matrix elements of operators containing both heavy quark (Q) and light quark (q) fields can contain large logarithms of the type ln(mQ2/μ2), where μ is a typical QCD mass scale and mQ is the heavy quark mass. We outline a method for summing leading logarithms of this type. We apply it to the decay constant fM of a low lying pseudoscalar meson M with Q̄q flavor quantum numbers and predict the ratios of decay constants for mesons with different heavy flavors. We also apply it to a matrix element of a four-quark operator which is relevant for B0−B̄0 mixing.https://resolver.caltech.edu/CaltechAUTHORS:20161018-091807641Effective field theory approach to processes involving both light and heavy fields
https://resolver.caltech.edu/CaltechAUTHORS:20161018-092313204
Year: 1988
DOI: 10.1016/0370-2693(88)90656-9
The matrix elements of operators containing both heavy quark (Q) fields and light particle fields can contain logarithms of the type In(mQμ) if (in some frame) the heavy quark is approximately static (i.e., |pQ|⪡mQ) and the light particles' typical momentum is of order μ⪡mQ. By performing the functional integral over the heavy quark fields first and treating their mass as very large (so that the heavy quarks are essentially static color sources), the logarithms of (mQμ) are determined by the "infinite" parts of Feynman diagrams involving only the light fields. We show how to sum these logarithms using a renormalization group equation derived from a mass-independent subtraction scheme.https://resolver.caltech.edu/CaltechAUTHORS:20161018-092313204Semileptonic B and D decays in the quark model
https://resolver.caltech.edu/CaltechAUTHORS:ISGprd89
Year: 1989
DOI: 10.1103/PhysRevD.39.799
We predict the matrix elements and resulting electron spectra for semileptonic meson decays using the quark potential model. Particular attention is paid to the high-energy electron end-point region in B decay since it is crucial to a determination of the b→u weak mixing angle. It is argued that in this region the usual inclusive ("quark decay") calculations are unjustified and must be replaced by explicit sums over decays of the original meson into low-mass exclusive hadronic final states.https://resolver.caltech.edu/CaltechAUTHORS:ISGprd89Wormholes in spacetime and θQCD
https://resolver.caltech.edu/CaltechAUTHORS:20170810-153648292
Year: 1989
DOI: 10.1016/0370-2693(89)90913-1
We calculate in chiral perturbation theory the dependence of Newton's gravitational constant G on the θ parameter of quantum chromodynamics, and we find that G, as a function of θ, is minimized at θ≌π. This calculation suggests that quantum fluctuations in the topology of spacetime would cause θ to assume a value very near π, contrary to the phenomenological evidence indicating that θ is actually near 0.https://resolver.caltech.edu/CaltechAUTHORS:20170810-153648292SU(3) predictions for nonleptonic B-meson decays
https://resolver.caltech.edu/CaltechAUTHORS:SAVprd89a
Year: 1989
DOI: 10.1103/PhysRevD.39.3346
The smallness of the up-, down-, and strange-quark masses compared with the QCD scale makes SU(3) flavor an approximate symmetry of the strong interactions. The B-, B0, and Bs0 mesons form a 3¯ representation of SU(3). Using the SU(3) transformation properties of the effective Hamiltonian for weak nonleptonic B-meson decays, relations are derived between B-meson decay amplitudes. Some of these relations may provide information on the importance of various competing effects that can occur in nonleptonic B-meson decays.https://resolver.caltech.edu/CaltechAUTHORS:SAVprd89aEffective hamiltonian for the electric dipole moment of the neutron
https://resolver.caltech.edu/CaltechAUTHORS:20170811-073546202
Year: 1990
DOI: 10.1016/0370-2693(90)91874-B
Recently it has been shown that, in extensions of the minimal standard model, the effective hamiltonian for the electric dipole moment of the neutron contains the dimension-six operator [TrGGG] (with G the gluon field strength tensor and G its dual) and that the effects of this operator are not suppressed by light (up, down and strange) quark masses. We note that at the weak-scale this effective hamiltonian also contains the dimension-six operator m_b bσ_(μν) G_(μν)b (with b the bottom quark field and m_b its mass) whose effects do not vanish in the chiral limit. We calculate in models with weveral Higgs doublets the influence of this operator on low energy physics, showing that when the heavy bottom quark is integrated out, it induces the operator [TrGGG].https://resolver.caltech.edu/CaltechAUTHORS:20170811-073546202Spectrum of baryons with two heavy quarks
https://resolver.caltech.edu/CaltechAUTHORS:20170906-093518077
Year: 1990
DOI: 10.1016/0370-2693(90)90035-5
Antibaryons with flavor quantum numbers QQq, where Q is a heavy quark and q a light quark, have the two heavy antiquarks weakly bound into a small (compared with the QCD scale) color triplet system. Since the interactions of heavy color triplet objects with the light degrees of freedom (i.e. quarks and gluons) are independent of the heavy color triplet's spin and mass, the spectrum of baryons with two heavy quarks can be related to the spectrum of mesons with Qq flavor quantum numbers.https://resolver.caltech.edu/CaltechAUTHORS:20170906-093518077Polarization in K^+ → π^+μ^+μ^−
https://resolver.caltech.edu/CaltechAUTHORS:20170906-094954136
Year: 1990
DOI: 10.1016/0370-2693(90)91170-G
The parity violating asymmetry [(Γ_R−Γ_L)/(Γ_R+Γ_L)], where Γ_R and Γ_L are the rates to produce right handed and left handed μ^+ in the decay K^+ → π^+μ^+μ^−, is discussed. We examine the contribution to this asymmetry from the interference of the "Z-penguin" and "W-box" with the standard one-photon contribution in the minimal standard model and in models with two Higgs doublets. The asymmetry is sensitive to extensions of the Higgs sector. Time reversal violating polarization effects are also considered. We show that the polarization of the μ^+ perpendicular to the μ^+μ^− decay plane is small.https://resolver.caltech.edu/CaltechAUTHORS:20170906-094954136Perturbative corrections to factorization in B decay
https://resolver.caltech.edu/CaltechAUTHORS:20160916-103224799
Year: 1991
DOI: 10.1016/0370-2693(91)91914-H
The amplitudes for processes like B → Dπ− and B → D∗π− are dominated by factorizable contributions wh relate these amplitudes to the semileptonic form factors in B → Deve and B → D∗eve. Factorization, together w heavy quark symmetry, leads to absolute predictions for ratios of decay rates. For example, Γ(B → Dπ−)Γ(B → D∗π−) = 1. We calculate perturbative strong interaction corrections to factorization and discuss their influence on the ration of decay rates Γ(B → Dπ−)/Γ(B → D∗π−). The decays B → Dϱ− and B → D∗ϱ− are also discussed.https://resolver.caltech.edu/CaltechAUTHORS:20160916-103224799Kaon condensation in nuclear matter
https://resolver.caltech.edu/CaltechAUTHORS:20161014-172423074
Year: 1991
DOI: 10.1016/0370-2693(91)90570-G
Using the leading operators in the chiral lagrangian for meson-baryon interactions (at low momentum) and treating the meson fields classically, Kaplan and Nelson have observed, using numerical methods, that a charged kaon condensate forms at several times nuclear density. We derive an analytical expression for the critical density. The effects of virtual mesons and higher dimension operators are discussed. The possibility of a neutral kaon condensate is also considered.https://resolver.caltech.edu/CaltechAUTHORS:20161014-172423074CP Violation
https://resolver.caltech.edu/CaltechAUTHORS:20201023-102057143
Year: 1992
DOI: 10.1007/978-3-642-84741-7_8
The possibility of determining the unitarity triangle from measurements of CP conserving quantities is discussed. The predictions of the minimal standard model for CP violation in the Kaon system and B-bar decays are reviewed. Electric dipole moments of the neutron and the electron in models with an extended Higgs sector are discussed.https://resolver.caltech.edu/CaltechAUTHORS:20201023-102057143Heavy quark symmetry
https://resolver.caltech.edu/CaltechAUTHORS:20201005-091734628
Year: 1992
DOI: 10.1142/9789814503587_0004
New symmetries of the strong interactions appear in heavy quark physics. They can be used to predict many properties of hadrons containing a single heavy quark. Some of these predictions are expected to play an important role in determining the values of elements of the Cabibbo-Kobayashi-Maskawa matrix.https://resolver.caltech.edu/CaltechAUTHORS:20201005-091734628Charged pion condensation in the chiral limit
https://resolver.caltech.edu/CaltechAUTHORS:20161018-093333924
Year: 1992
DOI: 10.1016/0550-3213(92)90109-O
We examine, in the chiral limit where the up and down quark masses are vanishingly small, the stability of the pure neutron ground state to small fluctuations due to charge and baryon number conserving strong interactions. It is shown that the ground state energy density as a function of pion field expectation value is determined by Weinberg's baryon two-body potential and by a calculable neutron-proton mass difference in the medium. This provides some insight into the competing physical effects that play a role in determining whether a charged pion condensate forms in dense nuclear matter. We find that in the chiral limit these effects suppress charged pion condensation.https://resolver.caltech.edu/CaltechAUTHORS:20161018-093333924Baryons containing a heavy quark as solitons
https://resolver.caltech.edu/CaltechAUTHORS:20170408-154531465
Year: 1993
DOI: 10.1016/0550-3213(93)90256-O
The possibility of interpreting baryons containing a single heavy quark as bound states of solitons (that arise in the non-linear sigma model) and heavy mesons is explored. Particular attention is paid to the parity of the bound states and to the role of heavy quark symmetry.https://resolver.caltech.edu/CaltechAUTHORS:20170408-154531465Chiral Perturbation Theory for Vector Mesons
https://resolver.caltech.edu/CaltechAUTHORS:20170408-170817697
Year: 1995
DOI: 10.1103/PhysRevLett.75.2272
We derive a heavy vector-meson chiral Lagrangian in which the vector mesons are treated as heavy static matter fields. The unknown couplings of the chiral Lagrangian are further related using the 1/N_c expansion. Chiral perturbation theory is applied to the vector-meson mass matrix. At one loop there are large corrections to the individual vector-meson masses, but the singlet-octet mixing angle remains almost unchanged. The parity-violating s-wave φ→ρπ weak decay amplitude is derived in the combined chiral and large N_c limits. Rare φ decays provide a sensitive test of nonleptonic neutral current structure.https://resolver.caltech.edu/CaltechAUTHORS:20170408-170817697Hyperon masses in nuclear matter
https://resolver.caltech.edu/CaltechAUTHORS:SAVprd96
Year: 1996
DOI: 10.1103/PhysRevD.53.349
We analyze hyperon and nucleon mass shifts in nuclear matter using chiral perturbation theory. Expressions for the mass shifts that include strong interaction effects at leading order in the density are derived. Corrections to our results are suppressed by powers of the Fermi momentum divided by either the chiral symmetry breaking scale or the nucleon mass. Our work is relevant for neutron stars and for large hypernuclei.https://resolver.caltech.edu/CaltechAUTHORS:SAVprd96Chiral perturbation theory for τ→ρπντ, τ→K*πντ, and τ→ωπντ
https://resolver.caltech.edu/CaltechAUTHORS:DAVprd96
Year: 1996
DOI: 10.1103/PhysRevD.53.2523
We use heavy vector meson SU(2)L×SU(2)R chiral perturbation theory to predict differential decay distributions for τ→ρπντ and τ→K*πντ in the kinematic region where pV·pπ/mV (here V=ρ or K*) is much smaller than the chiral symmetry-breaking scale. We also predict the rate for τ→ωπντ in this region (now V=ω). Comparing our prediction with experimental data, we determine one of the coupling constants in the heavy vector meson chiral Lagrangian.https://resolver.caltech.edu/CaltechAUTHORS:DAVprd96Final-state interactions and CP violation in KL→π+π- e+e-
https://resolver.caltech.edu/CaltechAUTHORS:ELWprd96a
Year: 1996
DOI: 10.1103/PhysRevD.53.4078
Using chiral perturbation theory we calculate the imaginary parts of the KL→π+π-e+e- form factors that arise from ππ→π+π- and ππ→π+π-γ* rescattering. We discuss their influence on CP-violating variables in KL→π+π-e+e-.https://resolver.caltech.edu/CaltechAUTHORS:ELWprd96a|Vub| from exclusive B and D decays
https://resolver.caltech.edu/CaltechAUTHORS:LIGprd96
Year: 1996
DOI: 10.1103/PhysRevD.53.4937
We propose a model-independent method to determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |Vub| from exclusive B and D decays. Combining information obtainable from B→ρlν¯l, B→K*νν¯, D→ρl¯νl, and D→K*l¯νl, a determination of |Vub| is possible, with an uncertainty from theory of around 10%. Theoretical uncertainties in the B→K*ll¯ decay rate are discussed.https://resolver.caltech.edu/CaltechAUTHORS:LIGprd96Kinematic enhancement of non-perturbative corrections to quarkonium production
https://resolver.caltech.edu/CaltechAUTHORS:20170408-143640730
Year: 1997
DOI: 10.1016/S0370-2693(97)00832-0
In this letter we address issues involved in quarkonium production near the boundaries of phase space. It is shown that higher-order non-perturbative contributions are enhanced in this kinematic region and lead to a breakdown of the non-relativistic (NRQCD) expansion. This breakdown is a consequence of sensitivity to the kinematics of soft gluon radiation and to the difference between partonic and hadronic phase space. We show how these large corrections can be resummed giving the dominant contribution to the cross section. The resummation leads to the introduction of non-perturbative, universal distribution functions. We discuss the importance of these shape functions for several observables, in particular the energy distribution of photo-produced J_ψ close to the endpoint.https://resolver.caltech.edu/CaltechAUTHORS:20170408-143640730Semileptonic B decays to excited charmed mesons
https://resolver.caltech.edu/CaltechAUTHORS:LEIprd98a
Year: 1998
DOI: 10.1103/PhysRevD.57.308
Exclusive semileptonic B decays into excited charmed mesons are investigated at order ΛQCD/mQ in the heavy quark effective theory. Differential decay rates for each helicity state of the four lightest excited D mesons (D1, D2*, D0*, and D1*) are examined. At zero recoil, ΛQCD/mQ corrections to the matrix elements of the weak currents can be written in terms of the leading Isgur-Wise functions for the corresponding transition and meson mass splittings. A model independent prediction is found for the slope parameter of the decay rate into helicity zero D1 at zero recoil. The differential decay rates are predicted, including ΛQCD/mQ corrections with some model dependence away from zero recoil and including order αs corrections. Ratios of various exclusive branching ratios are computed. Matrix elements of the weak currents between B mesons and other excited charmed mesons are discussed at zero recoil to order ΛQCD/mQ. These amplitudes vanish at leading order, and can be written at order ΛQCD/mQ in terms of local matrix elements. Applications to B decay sum rules and factorization are presented.https://resolver.caltech.edu/CaltechAUTHORS:LEIprd98aBulk fields in the Randall-Sundrum compactification scenario
https://resolver.caltech.edu/CaltechAUTHORS:GOLprd99
Year: 1999
DOI: 10.1103/PhysRevD.60.107505
Recently, Randall and Sundrum proposed a solution to the hierarchy problem where the background spacetime is five dimensional. There are two 3-branes, and the mass scale for fields that propagate on one of the 3-branes is exponentially suppressed relative to the fundamental scale of the theory, which is taken to be the Planck mass MPl. In this Brief Report we show that bulk fields with a five dimensional mass term of order MPl have, after integrating over the extra dimension, modes with four-dimensional masses that are exponentially suppressed as well. This opens the possibility that in this scenario the standard model matter fields may correspond to degrees of freedom that are not confined to a 3-brane.https://resolver.caltech.edu/CaltechAUTHORS:GOLprd99Phenomenology of a stabilized modulus
https://resolver.caltech.edu/CaltechAUTHORS:20170822-154242402
Year: 2000
DOI: 10.1016/S0370-2693(00)00099-X
We explore the phenomenology of a stabilized modulus field in the Randall-Sundrum scenario. It is found that if the large separation between branes arises from a small bulk scalar mass then the modulus (i.e. radion) is likely to be lighter than the lowest Kaluza-Klein excitations of bulk fields, and consequently may be the first direct signature of the model. Four-dimensional general covariance completely determines the couplings of the modulus to Standard Model fields. The strength of these couplings is determined by a single parameter which is set by the TeV rather than the Planck scale.https://resolver.caltech.edu/CaltechAUTHORS:20170822-154242402Generalized *-products, Wilson lines and the solution of the Seiberg-Witten equations
https://resolver.caltech.edu/CaltechAUTHORS:MEHjhep00
Year: 2001
DOI: 10.1088/1126-6708/2000/12/008
Higher order terms in the effective action of non-commutative gauge theories exhibit generalizations of the star-product (e.g. star' and star3). These terms do not manifestly respect the non-commutative gauge invariance of the tree level action. In U(1) gauge theories, we note that these generalized star-products occur in the expansion of some quantities that are invariant under non-commutative gauge transformations, but contain an infinite number of powers of the non-commutative gauge field. One example is an open Wilson line. Another is the expression for a commutative field strength tensor Fab in terms of the non-commutative gauge field hat Aa. Seiberg and Witten derived differential equations that relate commutative and non-commutative gauge transformations, gauge fields and field strengths. In the U(1) case we solve these equations neglecting terms of fourth order in hat A but keeping all orders in the non-commutative parameter θkl.https://resolver.caltech.edu/CaltechAUTHORS:MEHjhep00Supersymmetric correction to top quark pair production near threshold
https://resolver.caltech.edu/CaltechAUTHORS:20170823-083734394
Year: 2001
DOI: 10.1016/S0370-2693(01)00609-8
We studied the leading supersymmetric contribution to top–antitop threshold production using the NRQCD framework. The one-loop matching to the potential and the Wilson coefficient of the leading ^3S_1 production current were considered. We point out that the leading correction to the potential is zero due to SU(3)_c gauge invariance. This is true in general for any new physics that enters above the electroweak scale. The shape of the top quark pair production cross section is therefore almost unaffected near threshold, allowing a precise determination of the top quark mass based on the Standard Model calculations. The supersymmetric correction to the Wilson coefficient c_1 of the production current decouples for heavy super particles. Its contribution is smaller than the Standard Model next-to-next-leading-log results.https://resolver.caltech.edu/CaltechAUTHORS:20170823-083734394The long range gravitational potential energy between strings
https://resolver.caltech.edu/CaltechAUTHORS:20170823-084945261
Year: 2001
DOI: 10.1016/S0370-2693(01)01360-0
We calculate the gravitational potential energy between infinitely long parallel strings with tensions τ1 and τ2. Classically, it vanishes, but at one loop, we find that the long range gravitational potential energy per unit length is U/L=24G_N^2τ_1τ_2/(5πa^2)+⋯, where a is the separation between the strings, G_N is Newton's constant, and we set ℏ=c=1. The ellipses represent terms suppressed by more powers of G_Nτ_i. Typically, massless bulk fields give rise at one loop to a long range potential between p-branes in space–times of dimension p+2+1. The contribution to this potential from bulk scalars is computed for arbitrary p (strings correspond to p=1) and in the case of three-branes its possible relevance for cosmological quintessence is commented on.https://resolver.caltech.edu/CaltechAUTHORS:20170823-084945261Dedication to Nathan Isgur
https://resolver.caltech.edu/CaltechAUTHORS:20111110-090716046
Year: 2002
DOI: 10.1063/1.1478815
Nathan passed away in July after a lengthy illness. I am sure most of you are familiar
with his many contributions to heavy quark physics and it is certainly fitting that we
take a few minutes to honor him at the beginning of this meeting. Actually Nathan's
main physics interest was the strong interactions rather than heavy quark physics per
se. He was already very well known for work he did with Gabriel Karl and others on
the nonrelativistic quark model before the work that he did on heavy quark symmetry
and its applications. However, Nathan understood the limitations of the nonrelativistic
quark model, and was thrilled that the methods he helped develop allowed one to derive
systematically from the theory of the strong interactions many properties of hadrons that
contain a heavy quark.https://resolver.caltech.edu/CaltechAUTHORS:20111110-090716046Enhanced subleading structure functions in semileptonic B decay
https://resolver.caltech.edu/CaltechAUTHORS:20170408-172702759
Year: 2002
DOI: 10.1016/S0370-2693(02)02097-X
The charged lepton spectrum in semileptonic B→X_uℓν̄ decay near maximal lepton energy receives important corrections from subleading structure functions that are formally suppressed by powers of Λ_(QCD)/m_b but are enhanced by numerical factors. We investigate the series of higher order terms which smear over a region of width ΔE_ℓ∼Λ_(QCD) near the endpoint the contributions proportional to δ(E_ℓ−(m_b)/2) times (i) the matrix element of the chromomagnetic operator, and (ii) four-quark operators. These contribute to the total rate at the few percent level, but affect the endpoint region much more significantly. Implications for the determination of |V_(ub)| are discussed.https://resolver.caltech.edu/CaltechAUTHORS:20170408-172702759Hadronic Light-by-Light Contribution to Muon g - 2 in Chiral Perturbation Theory
https://resolver.caltech.edu/CaltechAUTHORS:RAMprl02
Year: 2002
DOI: 10.1103/PhysRevLett.89.041601
We compute the hadronic light-by-light scattering contributions to the muon anomalous magnetic moment, aμLL(had), in chiral perturbation theory that are enhanced by large logarithms and a factor of NC. They depend on a low-energy constant constrained by η→μ+μ- and π0→e+e- branching ratios. However, the dependence of aμLL(had) on nonlogarithmically enhanced effects cannot be constrained except through the measurement of the anomalous moment itself.https://resolver.caltech.edu/CaltechAUTHORS:RAMprl02Gradient instability for ω < - 1
https://resolver.caltech.edu/CaltechAUTHORS:20170710-131411758
Year: 2004
DOI: 10.1016/j.physletb.2004.07.025
We show that in single scalar field models of the dark energy with equations of state satisfying w ≡ p/ρ < − 1, the effective Lagrangian for fluctuations about the homogeneous background has a wrong sign spatial kinetic term. In most cases, spatial gradients are ruled out by microwave background observations. The sign of w + 1 is not connected to the sign of the time derivative kinetic term in the effective Lagrangian.https://resolver.caltech.edu/CaltechAUTHORS:20170710-131411758How Magnetic is the Dirac Neutrino?
https://resolver.caltech.edu/CaltechAUTHORS:BELprl05
Year: 2005
DOI: 10.1103/PhysRevLett.95.151802
We derive model-independent, "naturalness" upper bounds on the magnetic moments µnu of Dirac neutrinos generated by physics above the scale of electroweak symmetry breaking. In the absence of fine-tuning of effective operator coefficients, we find that current information on neutrino mass implies that |µnu|<~10-14 bohr magnetons. This bound is several orders of magnitude stronger than those obtained from analyses of solar and reactor neutrino data and astrophysical observations.https://resolver.caltech.edu/CaltechAUTHORS:BELprl05Towards a high-energy theory for the Higgs phase of gravity
https://resolver.caltech.edu/CaltechAUTHORS:GRAprd05
Year: 2005
DOI: 10.1103/PhysRevD.72.115016
Spontaneous Lorentz violation due to a time-dependent expectation value for a massless scalar has been suggested as a method for dynamically generating dark energy. A natural candidate for the scalar is a Goldstone boson arising from the spontaneous breaking of a U(1) symmetry. We investigate the low-energy effective action for such a Goldstone boson in a general class of models involving only scalars, proving that if the scalars have standard kinetic terms then at the classical level the effective action does not have the required features for spontaneous Lorentz violation to occur asymptotically (t-->[infinity]) in an expanding Friedman-Robertson-Walker universe. Then we study the large N limit of a renormalizable field theory with a complex scalar coupled to massive fermions. In this model an effective action for the Goldstone boson with the properties required for spontaneous Lorentz violation can be generated. Although the model has shortcomings, we feel it represents progress towards finding a high energy completion for the Higgs phase of gravity.https://resolver.caltech.edu/CaltechAUTHORS:GRAprd05Renormalization of the vector current in QED
https://resolver.caltech.edu/CaltechAUTHORS:COLprd06.834
Year: 2006
DOI: 10.1103/PhysRevD.73.105019
It is commonly asserted that the electromagnetic current is conserved and therefore is not renormalized. Within QED we show (a) that this statement is false, (b) how to obtain the renormalization of the current to all orders of perturbation theory, and (c) how to correctly define an electron number operator. The current mixes with the four-divergence of the electromagnetic field-strength tensor. The true electron number operator is the integral of the time component of the electron number density, but only when the current differs from the [overline MS]-renormalized current by a definite finite renormalization. This happens in such a way that Gauss's law holds: the charge operator is the surface integral of the electric field at infinity. The theorem extends naturally to any gauge theory.https://resolver.caltech.edu/CaltechAUTHORS:COLprd06.834Magnetic Moments of Dirac Neutrinos
https://resolver.caltech.edu/CaltechAUTHORS:BELaipcp06b
Year: 2006
DOI: 10.1063/1.2220408
The existence of a neutrino magnetic moment implies contributions to the neutrino mass via radiative corrections. We derive model-independent "naturalness" upper bounds on the magnetic moments of Dirac neutrinos, generated by physics above the electroweak scale. The neutrino mass receives a contribution from higher order operators, which are renormalized by operators responsible for the neutrino magnetic moment. This contribution can be calculated in a model independent way. In the absence of fine-tuning, we find that current neutrino mass limits imply that µv < 10^–14 Bohr magnetons. This bound is several orders of magnitude stronger than those obtained from solar and reactor neutrino data and astrophysical observations.https://resolver.caltech.edu/CaltechAUTHORS:BELaipcp06bFlavor changing neutral currents, an extended scalar sector, and the Higgs production rate at the CERN Large Hadron Collider
https://resolver.caltech.edu/CaltechAUTHORS:MANprd06b
Year: 2006
DOI: 10.1103/PhysRevD.74.035009
We study extensions of the standard model with additional colored scalar fields which can couple directly to quarks. Natural suppression of flavor changing neutral currents implies minimal flavor violation, and fixes the scalars to transform as (8,2)1/2 under the SU(3)×SU(2)×U(1) gauge symmetry. We explore the phenomenology of the standard model with one additional (8,2)1/2 scalar, and discuss how this extension can modify flavor physics and the Higgs boson production rate at the LHC. Custodial SU(2) symmetry can be implemented for the octet scalars since they transform as a real color representation. Additional weak scale degrees of freedom needed for gauge unification are discussed.https://resolver.caltech.edu/CaltechAUTHORS:MANprd06bMinimal extension of the standard model scalar sector
https://resolver.caltech.edu/CaltechAUTHORS:OCOprd07
Year: 2007
DOI: 10.1103/PhysRevD.75.037701
The minimal extension of the scalar sector of the standard model contains an additional real scalar field with no gauge quantum numbers. Such a field does not couple to the quarks and leptons directly but rather through its mixing with the standard model Higgs field. We examine the phenomenology of this model focusing on the region of parameter space where the new scalar particle is significantly lighter than the usual Higgs scalar and has small mixing with it. In this region of parameter space most of the properties of the additional scalar particle are independent of the details of the scalar potential. Furthermore the properties of the scalar that is mostly the standard model Higgs can be drastically modified since its dominant branching ratio may be to a pair of the new lighter scalars.https://resolver.caltech.edu/CaltechAUTHORS:OCOprd07Imprints of a primordial preferred direction on the microwave background
https://resolver.caltech.edu/CaltechAUTHORS:ACKprd07
Year: 2007
DOI: 10.1103/PhysRevD.75.083502
Rotational invariance is a well-established feature of low-energy physics. Violations of this symmetry must be extremely small today, but could have been larger in earlier epochs. In this paper we examine the consequences of a small breaking of rotational invariance during the inflationary era when the primordial density fluctuations were generated. Assuming that a fixed-norm vector picked out a preferred-direction during the inflationary era, we explore the imprint it would leave on the cosmic microwave background anisotropy, and provide explicit formulas for the expected amplitudes of the spherical-harmonic coefficients. We suggest that it is natural to expect that the imprint on the primordial power spectrum of a preferred spatial direction is approximately scale-invariant, and examine a simple model in which this is true.https://resolver.caltech.edu/CaltechAUTHORS:ACKprd07Color octet scalar production at the CERN LHC
https://resolver.caltech.edu/CaltechAUTHORS:GREprd07
Year: 2007
DOI: 10.1103/PhysRevD.76.075003
New physics at the weak scale that can couple to quarks typically gives rise to unacceptably large flavor changing neutral currents. An attractive way to avoid this problem is to impose the principle of minimal flavor violation. Recently it was noted that in minimal flavor violation only scalars with the same gauge quantum numbers as the standard model Higgs doublet or color octet scalars with the same weak quantum numbers as the Higgs doublet can couple to quarks. In this paper we compute the one-loop rate for production of a single color octet scalar through gluon fusion at the LHC, which can become greater than the tree level pair production rate for octet scalar masses around a TeV. We also calculate the precision electroweak constraint from Z-->[overline b]b; this constraint on color octet mass and Yukawa coupling affects the allowed range for single octet scalar production through gluon fusion.https://resolver.caltech.edu/CaltechAUTHORS:GREprd07Higgs decay width in multiscalar doublet models
https://resolver.caltech.edu/CaltechAUTHORS:MANprd08
Year: 2008
DOI: 10.1103/PhysRevD.77.013006
We show that there are regions of parameter space in multiscalar doublet models where, in the first few hundred inverse femtobarns of data, the new charged and neutral scalars are not directly observable at the LHC and yet the Higgs decay rate to b[overline b] is changed significantly from its standard model value. For a light Higgs with a mass less than 140 GeV, this can cause a large change in the number of two photon and tau+tau- Higgs decay events expected at the LHC compared to the minimal standard model. In the models we consider, the principle of minimal flavor violation is used to suppress flavor changing neutral currents. This paper emphasizes the importance of measuring the properties of the Higgs boson at the LHC; for a range of parameters the model considered has new physics at the TeV scale that is invisible, in the first few hundred inverse femtobarns of integrated luminosity at the LHC, except indirectly through the measurement of Higgs boson properties.https://resolver.caltech.edu/CaltechAUTHORS:MANprd08Flavor changing neutral currents in the Lee–Wick Standard Model
https://resolver.caltech.edu/CaltechAUTHORS:DULplb08
Year: 2008
DOI: 10.1016/j.physletb.2007.08.049
Recently an extension of the Standard Model (the Lee–Wick Standard Model) based on ideas of Lee and Wick (LW) was introduced. It does not contain quadratic divergences in the Higgs mass and hence solves the hierarchy puzzle. The LW Standard Model contains new heavy LW-resonances at the TeV scale that decay to ordinary particles. In this Letter we examine in more detail the flavor structure of the theory. We integrate out the heavy LW-fermions at tree level and find that this induces flavor changing Z-boson couplings. However, these flavor changing neutral currents are acceptably small since they are automatically suppressed by small Yukawa couplings. This is the case even though the theory does not satisfy the principle of minimal flavor violation. New couplings of the charged W-bosons to quarks and leptons are also induced. We also integrate out the LW–Higgs and examine the four-fermion operators induced.https://resolver.caltech.edu/CaltechAUTHORS:DULplb08The Lee-Wick standard model
https://resolver.caltech.edu/CaltechAUTHORS:GRIprd08a
Year: 2008
DOI: 10.1103/PhysRevD.77.025012
We construct a modification of the standard model which stabilizes the Higgs mass against quadratically divergent radiative corrections, using ideas originally discussed by Lee and Wick in the context of a finite theory of quantum electrodynamics. The Lagrangian includes new higher derivative operators. We show that the higher derivative terms can be eliminated by introducing a set of auxiliary fields; this allows for convenient computation and makes the physical interpretation more transparent. The theory is thought to be unitary, but nevertheless, it does not satisfy the usual analyticity conditions.https://resolver.caltech.edu/CaltechAUTHORS:GRIprd08aMassive vector scattering in Lee-Wick gauge theory
https://resolver.caltech.edu/CaltechAUTHORS:GRIprd08b
Year: 2008
DOI: 10.1103/PhysRevD.77.065010
We demonstrate that amplitudes describing scattering of longitudinally polarized massive vector bosons present in non-Abelian Lee-Wick gauge theory do not grow with energy and, hence, satisfy the constraints imposed by perturbative unitarity. This result contrasts with the widely known violation of perturbative unitarity in the standard model with a very heavy Higgs boson. Our conclusions are valid to all orders of perturbation theory and depend on the existence of a formulation of the theory in which all operators are of dimension four or less. This can be thought of as a restriction on the kinds of higher dimension operator which can be included in the higher derivative formulation of the theory.https://resolver.caltech.edu/CaltechAUTHORS:GRIprd08bClassical stability of a homogeneous, anisotropic inflating space-time
https://resolver.caltech.edu/CaltechAUTHORS:DULprd08
Year: 2008
DOI: 10.1103/PhysRevD.77.083510
We study the classical stability of an anisotropic space-time seeded by a spacelike, fixed-norm, dynamical vector field in a vacuum-energy-dominated inflationary era. It serves as a model for breaking isotropy during the inflationary era. We find that, for a range of parameters, the linear differential equations for small perturbations about the background do not have a growing mode. We also examine the energy of fluctuations about this background in flat space. If the kinetic terms for the vector field do not take the form of a field strength tensor squared, then there is a negative energy mode and the background is unstable. For the case where the kinetic term is of the form of a field strength tensor squared, we show that classical solutions to the equations of motion that are close to the background solution have energy greater than or equal to zero. This suggests that the background is metastable.https://resolver.caltech.edu/CaltechAUTHORS:DULprd08Neutrino masses in the Lee-Wick standard model
https://resolver.caltech.edu/CaltechAUTHORS:ESPprd08
Year: 2008
DOI: 10.1103/PhysRevD.77.085002
Recently, an extension of the standard model based on ideas of Lee and Wick has been discussed. This theory is free of quadratic divergences and hence has a Higgs mass that is stable against radiative corrections. Here, we address the question of whether or not it is possible to couple very heavy particles, with masses much greater than the weak scale, to the Lee-Wick standard model degrees of freedom and still preserve the stability of the weak scale. We show that in the LW-standard model the familiar seesaw mechanism for generating neutrino masses preserves the solution to the hierarchy puzzle provided by the higher derivative terms. The very heavy right-handed neutrinos do not destabilize the Higgs mass. We give an example of new heavy degrees of freedom that would destabilize the hierarchy, and discuss a general mechanism for coupling other heavy degrees of freedom to the Higgs doublet while preserving the hierarchy.https://resolver.caltech.edu/CaltechAUTHORS:ESPprd08Lee-Wick theories at high temperature
https://resolver.caltech.edu/CaltechAUTHORS:20090810-082606892
Year: 2009
DOI: 10.1016/j.physletb.2009.03.036
An extension of the standard model, the Lee–Wick standard model, based on ideas of Lee and Wick was
recently introduced. It does not contain quadratic divergences in the Higgs mass and hence solves the
hierarchy puzzle. The Lee–Wick standard model contains new heavy Lee–Wick resonances at the TeV
scale that decay to ordinary particles. In this Letter we examine the behavior of Lee–Wick resonances at
high temperature. We argue that they contribute negatively to the energy density ρ and pressure p and
at temperatures much greater than their mass M their O(T^4) contributions to ρ and p cancel against
those of the ordinary (light) particles. The remaining O(M2T^2) contributions are positive and result in
an equation of state that approaches w = 1 from below as T → ∞.https://resolver.caltech.edu/CaltechAUTHORS:20090810-082606892Trispectrum versus bispectrum in single-field inflation
https://resolver.caltech.edu/CaltechAUTHORS:20090813-132038823
Year: 2009
DOI: 10.1103/PhysRevD.79.103530
In the standard slow-roll inflationary cosmology, quantum fluctuations in a single field, the inflaton, generate approximately Gaussian primordial density perturbations. At present, the bispectrum and trispectrum of the density perturbations have not been observed and the probability distribution for these perturbations is consistent with Gaussianity. However, Planck satellite data will bring a new level of precision to bear on this issue, and it is possible that evidence for non-Gaussian effects in the primordial distribution will be discovered. One possibility is that a trispectrum will be observed without evidence for a nonzero bispectrum. It is not difficult for this to occur in inflationary models where quantum fluctuations in a field other than the inflaton contribute to the density perturbations. A natural question to ask is whether such an observation would rule out the standard scenarios. We explore this issue and find that it is possible to construct single-field models in which inflaton-generated primordial density perturbations have an observable trispectrum, but a bispectrum that is too small to be observed by the Planck satellite. However, an awkward fine-tuning seems to be unavoidable.https://resolver.caltech.edu/CaltechAUTHORS:20090813-132038823Causality as an emergent macroscopic phenomenon: The Lee-Wick O(N) model
https://resolver.caltech.edu/CaltechAUTHORS:20090729-111648871
Year: 2009
DOI: 10.1103/PhysRevD.79.105019
In quantum mechanics the deterministic property of classical physics is an emergent phenomenon appropriate only on macroscopic scales. Lee and Wick introduced Lorentz invariant quantum theories where causality is an emergent phenomenon appropriate for macroscopic time scales. In this paper we analyze a Lee-Wick version of the O(N) model. We argue that in the large-N limit this theory has a unitary and Lorentz invariant S matrix and is therefore free of paradoxes in scattering experiments. We discuss some of its acausal properties.https://resolver.caltech.edu/CaltechAUTHORS:20090729-111648871On the origin of neutrino masses
https://resolver.caltech.edu/CaltechAUTHORS:20091102-150149782
Year: 2009
DOI: 10.1103/PhysRevD.80.053006
We discuss the simplest mechanisms for generating neutrino masses at tree level and one loop level. We find a significant number of new possibilities where one can generate neutrino masses at the one-loop level by adding only two new types of representations. These models have renormalizable interactions that automatically conserve baryon number. Adding to the minimal standard model a scalar color octet with SU(3)⊗SU(2)⊗U(1) quantum numbers, (8,2,1/2), and a fermionic color octet in the fundamental or adjoint representation of SU(2), one can generate neutrino masses in agreement with experiment. Signals at the LHC and constraints from flavor violation are briefly discussed.https://resolver.caltech.edu/CaltechAUTHORS:20091102-150149782Inflaton two-point correlation in the presence of a cosmic string
https://resolver.caltech.edu/CaltechAUTHORS:20100105-101518370
Year: 2009
DOI: 10.1103/PhysRevD.80.103512
Precise measurements of the microwave background anisotropy have confirmed the inflationary picture of approximately scale invariant, Gaussian primordial adiabatic density perturbations. However, there are some anomalies that suggest a small violation of rotational and/or translational invariance in the mechanism that generates the primordial density fluctuations. Motivated by this we study the two-point correlation of a massless scalar (the inflaton) when the stress tensor contains the energy density from an infinitely long straight cosmic string in addition to a cosmological constant.https://resolver.caltech.edu/CaltechAUTHORS:20100105-101518370Asymmetric monetary policy and the yield curve
https://resolver.caltech.edu/CaltechAUTHORS:20100503-151247477
Year: 2009
DOI: 10.1016/j.jimonfin.2009.09.001
We discuss the Taylor rule near low inflation and interest rates.
Using an additional option-like term in the Federal Reserve's loss
function (i.e., the ''deflation put'') we extend the classic Taylor rule
to one with an asymmetric response that is more accommodative
when the inflation rate is very low. Once calibrated, this payoff
profile gives an exact, and easily communicable prescription for
Federal Reserve policy under regimes of low inflation. Simple
models of central bank behavior can produce highly complex yield
curve shapes. Using the usual Taylor rule and our proposed
extension as building blocks, we construct a robust framework for
generating realistic yield curves and the evolution of the economy.
Our main focus is the impact on the yield curve and the economy
of the ''deflation put''. We find that for economies like the U.S. the
deflation put reduces yields for all maturities. We also find that in
highly leveraged economies (such as Japan) the consequence of an
asymmetric deflation fighting policy may result in improved
economic conditions, but also raises the possibility of higher longterm
yields as a consequence.https://resolver.caltech.edu/CaltechAUTHORS:20100503-151247477The Lee-Wick standard model
https://resolver.caltech.edu/CaltechAUTHORS:20100301-104059728
Year: 2010
DOI: 10.1142/S0217751X10048871
This article reviews some recent work on a version of the standard model (the Lee-Wick standard model) that contains higher derivative kinetic terms that improve the convergence of loop diagrams removing the quadratic divergence in the Higgs boson mass. Naively higher derivative theories of this type are not acceptable since the higher derivative terms either cause instabilities (from negative energies) or a loss of unitarity (from negative norm states). Lee and Wick provided an interpretation for such theories arguing that theories with higher derivative kinetic terms can be unitary and stable if the states associated with the massive propagator poles, that arise from the higher derivatives, have widths and hence decay and are not in the spectrum of the theory.https://resolver.caltech.edu/CaltechAUTHORS:20100301-104059728Scalar representations and minimal flavor violation
https://resolver.caltech.edu/CaltechAUTHORS:20100216-112909655
Year: 2010
DOI: 10.1007/JHEP01(2010)073
We discuss the representations that new scalar degrees of freedom (beyond those in the minimal standard model) can have if they couple to quarks in a way that is consistent with minimal flavor violation. If the new scalars are singlets under the flavor group then they must be color singlets or color octets. In this paper we discuss the allowed representations and renormalizable couplings when the new scalars also transform under the flavor group. We find that color 3 and 6 representations are also allowed. We focus on the cases where the new scalars can have renormalizable Yukawa couplings to the quarks without factors of the quark Yukawa matrices. The renormalizable couplings in the models we introduce automatically conserve baryon number.https://resolver.caltech.edu/CaltechAUTHORS:20100216-112909655Translational invariance and the anisotropy of the cosmic microwave background
https://resolver.caltech.edu/CaltechAUTHORS:20100524-141735641
Year: 2010
DOI: 10.1103/PhysRevD.81.083501
Primordial quantum fluctuations produced by inflation are conventionally assumed to be statistically
homogeneous, a consequence of translational invariance. In this paper we quantify the potentially
observable effects of a small violation of translational invariance during inflation, as characterized by
the presence of a preferred point, line, or plane.We explore the imprint such a violation would leave on the
cosmic microwave background anisotropy, and provide explicit formulas for the expected amplitudes <а_(lm)а^*_(l'm')> of the spherical-harmonic coefficients.https://resolver.caltech.edu/CaltechAUTHORS:20100524-141735641On theories of enhanced CP violation in B_(s,d) meson mixing
https://resolver.caltech.edu/CaltechAUTHORS:20110105-105917873
Year: 2010
DOI: 10.1007/JHEP11(2010)157
The DØ collaboration has measured a deviation from the standard model (SM) prediction in the like sign dimuon asymmetry in semileptonic b decay with a significance of 3.2 σ. We discuss how minimal flavour violating (MFV) models with multiple scalar representations can lead to this deviation through tree level exchanges of new MFV scalars. We review how the two scalar doublet model can accommodate this result and discuss some of its phenomenology. Limits on electric dipole moments suggest that in this model the coupling of the charged scalar to the right handed u-type quarks is suppressed while its coupling to the d-type right handed quarks must be enhanced. We construct an extension of the MFV two scalar doublet model where this occurs naturally.https://resolver.caltech.edu/CaltechAUTHORS:20110105-105917873Standard model vacua for two-dimensional compactifications
https://resolver.caltech.edu/CaltechAUTHORS:20110315-091122483
Year: 2010
DOI: 10.1007/JHEP12(2010)083
We examine the structure of lower-dimensional standard model vacua for two-dimensional compactications (on a 2D torus and on a 2D sphere). In the case of the torus we find a new standard model vacuum for a large range of neutrino masses consistent with experiment. Quantum effects play a crucial role in the existence of this vacuum. For the
compactification on a sphere the classical terms dominate the effective potential for large radii and a stable vacuum is achieved only by introducing a large magnetic flux. We argue that there are no two-dimensional standard model vacua for compactifications on a surface of genus greater than one.https://resolver.caltech.edu/CaltechAUTHORS:20110315-091122483Dark matter, baryon asymmetry, and spontaneous B and L breaking
https://resolver.caltech.edu/CaltechAUTHORS:20110301-113227913
Year: 2011
DOI: 10.1103/PhysRevD.83.023520
We investigate the dark matter and the cosmological baryon asymmetry in a simple theory where baryon (B) and lepton (L) number are local gauge symmetries that are spontaneously broken. In this model, the cold dark matter candidate is the lightest new field with baryon number and its stability is an automatic consequence of the gauge symmetry. Dark matter annihilation is either through a leptophobic gauge boson whose mass must be below a TeV or through the Higgs boson. Since the mass of the leptophobic gauge boson has to be below the TeV scale, one finds that in the first scenario there is a lower bound on the elastic cross section of about 5×10^(-46) cm^2. Even though baryon number is gauged and not spontaneously broken until the weak scale, a cosmologically acceptable baryon excess is possible. There can be a tension between achieving both the measured baryon excess and the dark matter density.https://resolver.caltech.edu/CaltechAUTHORS:20110301-113227913Fourth generation bound states
https://resolver.caltech.edu/CaltechAUTHORS:20110502-112029805
Year: 2011
DOI: 10.1103/PhysRevD.83.074015
We investigate the spectrum and wave functions of q̅ ′q′ bound states for heavy fourth generation quarks (q′) that have a very small mixing with the three observed generations of standard model quarks. Such bound states come with different color, spin and flavor quantum numbers. Since the fourth generation Yukawa coupling, λ_q′, is
large we include all perturbative corrections to the potential between the heavy quark and antiquark of order λ_(q′)^(2)N_c/16π^2 where N_c is the number of colors, as well as relativistic corrections suppressed by (v/c)^2. We find that the lightest fourth generation quark masses for which a bound state exists for color octet states. For the color singlet states, which always have a bound state, we analyze the influence that the Higgs couplings have on the size and binding energy of the bound states.https://resolver.caltech.edu/CaltechAUTHORS:20110502-112029805Standard model with compactified spatial dimensions
https://resolver.caltech.edu/CaltechAUTHORS:20111007-100818958
Year: 2011
DOI: 10.1007/JHEP07(2011)086
We analyze the structure of the standard model coupled to gravity with spatial dimensions compactified on a three-torus. We find that there are no stable one-dimensional vacua at zero temperature, although there does exist an unstable vacuum for a particular set of Dirac neutrino masses.https://resolver.caltech.edu/CaltechAUTHORS:20111007-100818958Breaking local baryon and lepton number at the TeV scale
https://resolver.caltech.edu/CaltechAUTHORS:20111018-094046518
Year: 2011
DOI: 10.1007/JHEP08(2011)068
Simple models are proposed where the baryon and lepton number are gauged and spontaneously broken near the weak scale. The models use a fourth generation that is vector-like with respect to the strong, weak and electromagnetic interactions to cancel anomalies. One does not need large Yukawa couplings to be consistent with the experimental limits on fourth generation quark masses and hence the models are free of coupling constants with Landau poles near the weak scale. We discuss the main features of simple non-supersymmetric and supersymmetric models. In these models the light neutrino masses are generated through the seesaw mechanism and proton decay is forbidden even though B and L are broken near the weak scale. For some values of the parameters in these models baryon and/or lepton number violation can be observed at the Large Hadron Collider.https://resolver.caltech.edu/CaltechAUTHORS:20111018-094046518Low energy supersymmetry with baryon and lepton number gauged
https://resolver.caltech.edu/CaltechAUTHORS:20111004-123847329
Year: 2011
DOI: 10.1103/PhysRevD.84.055015
We investigate the spontaneous breaking of the Baryon (B) and Lepton (L) number at the TeV scale in supersymmetric models. A simple extension of the minimal supersymmetric standard model where B and L are spontaneously broken local gauge symmetries is proposed. The B and L symmetry breaking scales are defined by the supersymmetry breaking scale. By gauging B and L, we understand the absence of the baryon and lepton number violating interactions of dimension four and five in the minimal supersymmetric standard model. Furthermore, we show that even though these symmetries are spontaneously broken there are no dangerous operators mediating proton decay. We discuss the main properties of the spectrum, the possible baryon number violating decays and the implications for the dark matter candidates. In this model, one can have lepton number violating signals from the decays of the right-handed neutrinos and baryon number violating signals from the decays of squarks and gauginos without conflict with the bounds coming from proton decay, n-n̅ oscillations and dinucleon decays.https://resolver.caltech.edu/CaltechAUTHORS:20111004-123847329Higgs properties and fourth generation leptons
https://resolver.caltech.edu/CaltechAUTHORS:20111021-142612846
Year: 2011
DOI: 10.1103/PhysRevD.84.055025
It is possible that there are additional vectorlike generations where the quarks have mass terms that do not originate from weak symmetry breaking, but the leptons only get mass through weak symmetry breaking. We discuss the impact that the new leptons have on Higgs boson decay branching ratios and on the range of allowed Higgs masses in such a model (with a single new vectorlike generation). We find that if the fourth generation leptons are too heavy to be produced in Higgs decay, then the new leptons reduce the branching ratio for h→γγ to about 30% of its standard-model value. The dependence of this branching ratio on the new charged lepton masses is weak. Furthermore the expected Higgs production rate at the LHC is very near its standard-model value if the new quarks are much heavier than the weak scale. If the new quarks have masses near the cutoff for the theory, then for cutoffs greater than 10^(15) GeV, the new lepton masses cannot be much heavier than about 100 GeV and the Higgs mass must have a value around 175 GeV.https://resolver.caltech.edu/CaltechAUTHORS:20111021-142612846Simplified models with baryon number violation but no proton decay
https://resolver.caltech.edu/CaltechAUTHORS:20130503-094324688
Year: 2013
DOI: 10.1103/PhysRevD.87.075004
We enumerate the simplest models that have baryon number violation at the classical level but do not give rise to proton decay. These models have scalar fields in two representations of SU(3)×SU(2)×U(1) and violate baryon number by two units. Some of the models give rise to nn̅ (neutron-antineutron) oscillations, while some also violate lepton number by two units. We discuss the range of scalar masses for which nn̅ oscillations are measurable in the next generation of experiments. We give a brief overview of the phenomenology of these models and then focus on one of them for a more quantitative discussion of nn̅ oscillations, the generation of the cosmological baryon number, the electric dipole moment of the neutron, and K^0-K̅^0 mixing.https://resolver.caltech.edu/CaltechAUTHORS:20130503-094324688Baryon asymmetry and dark matter through the vector-like portal
https://resolver.caltech.edu/CaltechAUTHORS:20130904-132659017
Year: 2013
DOI: 10.1007/JHEP05(2013)094
A possible connection between the cosmological baryon asymmetry, dark matter and vector-like fermions is investigated. In this scenario an asymmetry generated through baryogenesis or leptogenesis (in the vector-like matter sector) connects the baryon asymmetry to the dark matter density. We present explicit renormalizable models where this connection occurs. These models have asymmetric dark matter and a significant invisible Higgs decay width to dark matter particles is possible. We refer to this type of scenario as the vector-like portal. In some asymmetric dark matter models there are potential naturalness issues for the low energy effective theory. We address that issue in themodels we consider by starting with a Lagrangian that is the most general renormalizable one consistent with the gauge (and discrete) symmetries and showing the low energy effective theory automatically has the required form as a consequence of the symmetries of the full theory. We show that the mass of the dark matter candidate is predicted in these scenarios.https://resolver.caltech.edu/CaltechAUTHORS:20130904-132659017Gauge Theory for Baryon and Lepton Numbers with Leptoquarks
https://resolver.caltech.edu/CaltechAUTHORS:20130718-102128997
Year: 2013
DOI: 10.1103/PhysRevLett.110.231801
Models where the baryon (B) and lepton (L) numbers are local gauge symmetries that are spontaneously
broken at a low scale are revisited. We find new extensions of the standard model which predict
the existence of fermions that carry both baryon and lepton numbers (i.e., leptoquarks). The local baryonic
and leptonic symmetries can be broken at a scale close to the electroweak scale and we do not need to
postulate the existence of a large desert to satisfy the experimental constraints on baryon number violating
processes like proton decay.https://resolver.caltech.edu/CaltechAUTHORS:20130718-102128997Color breaking in the early universe
https://resolver.caltech.edu/CaltechAUTHORS:20130812-151057238
Year: 2013
DOI: 10.1103/PhysRevD.88.015003
We explore the possibility that SU(3)_C was not an exact symmetry at all times in the early Universe, using minimal extensions of the standard model that contain a color triplet scalar field and perhaps other fields. We show that, for a range of temperatures, there can exist a phase in which the free energy is minimized when the color triplet scalar has a nonvanishing vacuum expectation value, spontaneously breaking color. At very high temperatures and at lower temperatures, color symmetry is restored. The breaking of color in this phase is accompanied by the spontaneous breaking of B - L if the color triplet scalar Yukawa couples to quarks and/or leptons. We discuss the requirements on the minimal extensions needed for consistency of this scenario with present collider bounds on new colored scalar particles.https://resolver.caltech.edu/CaltechAUTHORS:20130812-151057238Phenomenology of scalar leptoquarks
https://resolver.caltech.edu/CaltechAUTHORS:20130515-135302971
Year: 2013
DOI: 10.1103/PhysRevD.88.035009
We study the simplest renormalizable scalar leptoquark models where the standard model is augmented only by one additional scalar representation of SU(3)×SU(2)×U(1). The requirement that there be no proton decay from renormalizable interactions singles out two such models, one of which exhibits an unusual top mass enhancement of the μ→eγ decay rate. We analyze the phenomenology of the model with the unusual top mass enhancement of loop level chirality changing charged lepton processes in the light of existing and upcoming experiments. Both of the models that do not allow proton decay from renormalizable interactions have dimension-5 operators that, even if suppressed by the Planck scale, can give rise to an unacceptably high level of baryon number violation. We discuss symmetries that can forbid these dimension-5 operators.https://resolver.caltech.edu/CaltechAUTHORS:20130515-135302971Phenomenology of heavy vectorlike leptons
https://resolver.caltech.edu/CaltechAUTHORS:20131018-093200954
Year: 2013
DOI: 10.1103/PhysRevD.88.055009
We study the impact that a heavy generation of vectorlike leptons can have on the value of the electric dipole moment of the electron, and the rates for the flavor violating processes μ→eγ and μ→3e. The smallness of the charged lepton masses suggests that at least some of the Yukawa coupling constants of the vectorlike leptons to the ordinary leptons or amongst themselves are small, but even with such small couplings experiments trying to detect these quantities are sensitive to extra generation lepton masses up to about 100 TeV.https://resolver.caltech.edu/CaltechAUTHORS:20131018-093200954Low-scale quark-lepton unification
https://resolver.caltech.edu/CaltechAUTHORS:20131106-082506178
Year: 2013
DOI: 10.1103/PhysRevD.88.057703
We investigate the possibility that quarks and leptons are unified at a low energy scale much smaller than the grand unified scale. A simple theory for quark-lepton unification based on the gauge group SU(4)_C⊗SU(2)_L⊗U(1)_R is proposed. This theory predicts the existence of scalar leptoquarks which could be produced at the Large Hadron Collider. In order to have light neutrinos without fine-tuning, their masses are generated through the inverse seesaw mechanism.https://resolver.caltech.edu/CaltechAUTHORS:20131106-082506178Effective Theory and Simple Completions for Neutrino Interactions
https://resolver.caltech.edu/CaltechAUTHORS:20140505-131013279
Year: 2014
DOI: 10.1103/PhysRevD.90.053005
We consider all the dimension 6 operators as well as some simple extensions of the standard model that give new contributions to neutrino interactions with matter. Such interactions are usually parametrized by ϵ_(αβ), where α and β are neutrino flavor indices taking the values e, μ and τ. In the simple models we consider the ϵ_(αβ)'s are much more constrained than in the operator-based model-independent approach. Typically the ϵ_(αβ)'s are restricted to be smaller in magnitude than around 10^(−3). In some of the leptoquark models, a specific pattern for the leptoquark Yukawa couplings allows the diagonal element ϵ_(ττ) to be as large as ∼0.1, or one of ϵ_(ee), ϵ_(μμ)∼0.01. We discuss the interplay between neutrino physics and leptoquark searches at the LHC.https://resolver.caltech.edu/CaltechAUTHORS:20140505-131013279Stable Bound States of Asymmetric Dark Matter
https://resolver.caltech.edu/CaltechAUTHORS:20140804-083111315
Year: 2014
DOI: 10.1103/PhysRevD.90.055030
The simplest renormalizable effective field theories with asymmetric dark matter bound states contain
two additional gauge singlet fields, one being the dark matter and the other a mediator particle that the dark
matter annihilates into. We examine the physics of one such model with a Dirac fermion as the dark matter
and a real scalar mediator. For a range of parameters the Yukawa coupling of the dark matter to the mediator
gives rise to stable asymmetric dark matter bound states. We derive properties of the bound states including
nuggets formed from N ≫ 1 dark matter particles. We also consider the formation of bound states in the
early Universe and direct detection of dark matter bound states. Many of our results also hold for symmetric
dark matter.https://resolver.caltech.edu/CaltechAUTHORS:20140804-083111315Yukawa Bound States of a Large Number of Fermions
https://resolver.caltech.edu/CaltechAUTHORS:20141116-071612082
Year: 2015
DOI: 10.1007/JHEP02(2015)023
We consider the bound state problem for a field theory that contains a Dirac fermion x that Yukawa couples to a (light) scalar field ø. We are interested in bound states with a large number N of x particles. A Fermi gas model is used to numerically determine the dependence of the radius R of these bound states on N and also the dependence of the binding energy on N. Since scalar interactions with relativistic x's are suppressed two regimes emerge. For modest values of N the state is composed of non-relativistic x particles. In this regime as N increases R decreases. Eventually the core region becomes relativistic and the size of the state starts to increase as N increases. As a result, for fixed Yukawa coupling and x mass, there is a minimum sized state that occurs roughly at the value of N where the core region first becomes relativistic. As an application to dark matter, our analysis offers the possibility of having a supermassive thermal DM candidate. We also compute an elastic scattering form factor that can be relevant for direct detection if the dark matter is composed of such x particles.https://resolver.caltech.edu/CaltechAUTHORS:20141116-071612082New Vector-Like Fermions and Flavor Physics
https://resolver.caltech.edu/CaltechAUTHORS:20150812-194949578
Year: 2015
DOI: 10.1007/JHEP10(2015)027
We study renormalizable extensions of the standard model that contain vector-like fermions in a (single) complex representation of the standard model gauge group. There are 11 models where the vector-like fermions Yukawa couple to the standard model fermions via the Higgs field. These models do not introduce additional fine-tunings. They can lead to, and are constrained by, a number of different flavor-changing processes involving leptons and quarks, as well as direct searches. An interesting feature of the models with strongly interacting vector-like fermions is that constraints from neutral meson mixings (apart from CP violation in K^0–K^0 mixing) are not sensitive to higher scales than other flavor-changing neutral-current processes. We identify order 1/(4πM)^2 (where M is the vector-like fermion mass) one-loop contributions to the coefficients of the four-quark operators for meson mixing, that are not suppressed by standard model quark masses and/or mixing angles.https://resolver.caltech.edu/CaltechAUTHORS:20150812-194949578Effects of Bound States on Dark Matter Annihilation
https://resolver.caltech.edu/CaltechAUTHORS:20160411-175600335
Year: 2016
DOI: 10.1103/PhysRevD.93.115020
We study the impact of bound state formation on dark matter annihilation rates in models where dark matter interacts via a light mediator, the dark photon. We derive the general cross section for radiative capture into all possible bound states, and point out its nontrivial dependence on the dark matter velocity and the dark photon mass. For indirect detection, our result shows that dark matter annihilation inside bound states can play an important role in enhancing signal rates over the rate for direct dark matter annihilation with Sommerfeld enhancement. The effects are strongest for large dark gauge coupling and when the dark photon mass is smaller than the typical momentum of dark matter in the Galaxy. As an example, we show that for thermal dark matter the Fermi gamma ray constraint is substantially increased once bound state effects are taken into account. We also find that bound state effects are not important for dark matter annihilation during the freeze-out and recombination epochs.https://resolver.caltech.edu/CaltechAUTHORS:20160411-175600335Static spherically symmetric Kerr-Schild metrics and implications for the classical double copy
https://resolver.caltech.edu/CaltechAUTHORS:20160811-110734508
Year: 2016
DOI: 10.1103/PhysRevD.94.044023
We discuss the physical interpretation of stress-energy tensors that source static spherically symmetric Kerr-Schild metrics. We find that the sources of such metrics with no curvature singularities or horizons do not simultaneously satisfy the weak and strong energy conditions. Sensible stress-energy tensors usually satisfy both of them. Under most circumstances, these sources are not perfect fluids and contain shear stresses. We show that for these systems the classical double copy associates the electric charge density to the Komar energy density. In addition, we demonstrate that the stress-energy tensors are determined by the electric charge density and their conservation equations.https://resolver.caltech.edu/CaltechAUTHORS:20160811-110734508Strong CMB Constraint On P-Wave Annihilating Dark Matter
https://resolver.caltech.edu/CaltechAUTHORS:20160615-155545845
Year: 2017
DOI: 10.1016/j.physletb.2017.08.010
We consider a dark sector consisting of dark matter that is a Dirac fermion and a scalar mediator. This model has been extensively studied in the past. If the scalar couples to the dark matter in a parity conserving manner then dark matter annihilation to two mediators is dominated by the P-wave channel and hence is suppressed at very low momentum. The indirect detection constraint from the anisotropy of the Cosmic Microwave Background is usually thought to be absent in the model because of this suppression. In this letter we show that dark matter annihilation via bound state formation occurs through the S-wave and hence there is a constraint on the parameter space of the model from the Cosmic Microwave Background.https://resolver.caltech.edu/CaltechAUTHORS:20160615-155545845Quasi-single field inflation in the non-perturbative regime
https://resolver.caltech.edu/CaltechAUTHORS:20170721-093214273
Year: 2018
DOI: 10.1007/JHEP06(2018)105
In quasi-single field inflation there are massive fields that interact with the inflaton field. If these other fields are not much heavier than the Hubble constant during inflation (H) these interactions can lead to important consequences for the cosmological energy density perturbations. The simplest model of this type has a real scalar inflaton field that interacts with another real scalar S (with mass m). In this model there is a mixing term of the form μπS, where π is the Goldstone fluctuation that is associated with the breaking of time translation invariance by the time evolution of the inflaton field during the inflationary era. In this paper we study this model in the region (μ/H)^2 + (m/H)^2 > 9/4 and m/H∼O(1) or less. For a large part of the parameter space in this region standard perturbative methods are not applicable. Using numerical and analytic methods we study how large μ/H has to be for the large μ/H effective field theory approach to be applicable.https://resolver.caltech.edu/CaltechAUTHORS:20170721-093214273Lepton Flavorful Fifth Force and Depth-dependent Neutrino Matter Interactions
https://resolver.caltech.edu/CaltechAUTHORS:20180305-134624235
Year: 2018
DOI: 10.1007/JHEP06(2018)053
We consider a fifth force to be an interaction that couples to matter with a strength that grows with the number of atoms. In addition to competing with the strength of gravity a fifth force can give rise to violations of the equivalence principle. Current long range constraints on the strength and range of fifth forces are very impressive. Amongst possible fifth forces are those that couple to lepton flavorful charges L_e – L_μ or L_e – L_τ. They have the property that their range and strength are also constrained by neutrino interactions with matter. In this brief note we review the existing constraints on the allowed parameter space in gauged U(1)_(Le−Lμ,Lτ). We find two regions where neutrino oscillation experiments are at the frontier of probing such a new force. In particular, there is an allowed range of parameter space where neutrino matter interactions relevant for long baseline oscillation experiments depend on the depth of the neutrino beam below the surface of the earth.https://resolver.caltech.edu/CaltechAUTHORS:20180305-134624235Non-Gaussian Enhancements of Galactic Halo Correlations in Quasi-Single Field Inflation
https://resolver.caltech.edu/CaltechAUTHORS:20180129-091837898
Year: 2018
DOI: 10.1103/PhysRevD.97.123528
We consider a quasi-single field inflation model in which the inflaton interacts with a massive scalar field called the isocurvaton. Due to the breaking of time translational invariance by the inflaton background, these interactions induce kinetic mixing between the inflaton and isocurvaton, which is parameterized by a constant
μ
. We derive analytic formulas for the curvature perturbation two-, three-, four-, five-, and six-point functions explicitly in terms of the external wave vectors in the limit where
μ
and the mass of the isocurvaton
m
are both much smaller than
H
. In previous work, it has been noted that when
m
/
H
and
μ
/
H
are small, the non-Gaussianities predicted by quasi-single field inflation give rise to long wavelength enhancements of the power spectrum for biased objects (e.g., galactic halos). We review this calculation, and calculate the analogous enhanced contribution to the bispectrum of biased objects. We determine the scale at which these enhanced terms are larger than the Gaussian piece. We also identify the scaling of these enhanced parts to the n-point function of biased objects.https://resolver.caltech.edu/CaltechAUTHORS:20180129-091837898Stochastic Bias from Loops of Massive Particles During Inflation
https://resolver.caltech.edu/CaltechAUTHORS:20180109-161940287
Year: 2018
DOI: 10.1016/j.physletb.2018.06.026
Primordial non-Gaussianities enhanced at small wavevectors can induce a power spectrum of the galaxy overdensity that differs greatly from that of the matter overdensity at large length scales. In previous work, it was shown that "squeezed" three-point and "collapsed" four-point functions of the curvature perturbation ζ can generate these non-Gaussianities and give rise to so-called scale-dependent and stochastic bias in the galaxy overdensity power spectrum. We explore a third way to generate non-Gaussianities enhanced at small wavevectors: the infrared behavior of quantum loop contributions to the four-point correlations of ζ. We show that these loop effects can give the largest contributions to the four-point function of ζ in the collapsed limit and be observable in the context of quasi-single field inflation.https://resolver.caltech.edu/CaltechAUTHORS:20180109-161940287The Direct Coupling of Light Quarks to Heavy Di-quarks
https://resolver.caltech.edu/CaltechAUTHORS:20180912-092027955
Year: 2019
DOI: 10.1016/j.physletb.2018.11.004
In the limit m_Q > m_Q v_(rel) > m_Q v_(rel)^2 ≫ Λ_(QCD) hadronic states with two heavy quarks Qshould be describable by a version of HQET where the heavy quark is replaced by a di-quark degree of freedom. In this limit the di-quark is a small (compared with 1/ΛQCD) color anti-triplet, bound primarily by a color Coulomb potential. The excited Coulombic states and color six states are much heavier than the color anti-triplet ground state. The low lying spectrum of hadrons containing two heavy quarks is then determined by the coupling of the light quarks and gluons with momentum of order ΛQCD to this ground state di-quark. In this short paper we calculate the coefficient of leading local operator (S_v^†S_v)(qγ^μv_μq) that couples this color anti-triplet di-quark field S_v (with four-velocity v) directly to the light quarks q in the low energy effective theory. It is O(1/(α_s(m_Qv_(rel))m_Q^2)). While our work is mostly of pedagogical value we make an estimate of the contribution of this operator to the masses of Ξ_(bbq) baryon and T_(QQqq) tetraquark using the non-relativistic constituent quark model.https://resolver.caltech.edu/CaltechAUTHORS:20180912-092027955De-Sitter Quantum Loops as the origin of Primordial Non-Gaussianities
https://resolver.caltech.edu/CaltechAUTHORS:20180620-154220173
Year: 2019
DOI: 10.1103/PhysRevD.99.056007
It was recently pointed out that in some inflationary models quantum loops containing a scalar of mass m that couples to the inflaton can be the dominant source of primordial non-Gaussianities. We explore this phenomenon in the simplest such model focusing on the behavior of the primordial curvature fluctuations for small m/H. Explicit calculations are done for the three- and four-point curvature fluctuation correlations. Constraints on the parameters of the model from the cosmic microwave background limits on primordial non-Gaussianity are discussed. The bispectrum in the squeezed limit and the trispectrum in the compressed limit are examined. The form of the n-point correlations as any partial sum of wave vectors gets small is determined.https://resolver.caltech.edu/CaltechAUTHORS:20180620-154220173An Estimate of the Inclusive Branching Ratio to B_c in Ξ_(bbq) Decay
https://resolver.caltech.edu/CaltechAUTHORS:20190312-142253295
Year: 2019
DOI: 10.1016/j.physletb.2019.04.020
We estimate the branching ratio for the inclusive decays Ξ_(bbq) → B^((∗))_c+X_(c,s,q) to be approximately 1%. Our estimate is performed using non-relativistic potential quark model methods that are appropriate if the bottom and charm quarks are heavy compared to the strong interaction scale. Here the superscript (∗) denotes that we are summing over spin zero B_c and spin one B^∗_c mesons and the subscript q denotes a light quark. Our approach treats the two bottom quarks in the baryon Ξ_(bbq) as a small color anti-triplet. This estimate for the inclusive branching ratio to B_c and B^∗_c mesons also holds for decays of the lowest lying T_(bbqq) tetraquark states, provided they are stable against strong and electromagnetic decay.https://resolver.caltech.edu/CaltechAUTHORS:20190312-142253295Primordial Non-Gaussianity
https://resolver.caltech.edu/CaltechAUTHORS:20190925-095718211
Year: 2019
DOI: 10.48550/arXiv.1903.04409
Our current understanding of the Universe is established through the pristine measurements of structure in the cosmic microwave background (CMB) and the distribution and shapes of galaxies tracing the large scale structure (LSS) of the Universe. One key ingredient that underlies cosmological observables is that the field that sources the observed structure is assumed to be initially Gaussian with high precision. Nevertheless, a minimal deviation from Gaussianityis perhaps the most robust theoretical prediction of models that explain the observed Universe; itis necessarily present even in the simplest scenarios. In addition, most inflationary models produce far higher levels of non-Gaussianity. Since non-Gaussianity directly probes the dynamics in the early Universe, a detection would present a monumental discovery in cosmology, providing clues about physics at energy scales as high as the GUT scale.https://resolver.caltech.edu/CaltechAUTHORS:20190925-095718211Impact of transforming to conformal Fermi coordinates on quasisingle field non-Gaussianity
https://resolver.caltech.edu/CaltechAUTHORS:20200629-093206924
Year: 2020
DOI: 10.1103/PhysRevD.102.023533
In general relativity predictions for observable quantities can be expressed in a coordinate independent way. Nonetheless it may be inconvenient to do so. Using a particular frame may be the easiest way to connect theoretical predictions to measurable quantities. For the cosmological curvature bispectrum such frame is described by the Conformal Fermi Coordinates. In single field inflation it was shown that going to this frame cancels the squeezed limit of the density perturbation bispectrum calculated in Global Coordinates. We explore this issue in quasi single field inflation when the curvaton mass and the curvaton-inflaton mixing are small. In this case, the contribution to the bispectrum from the coordinate transformation to Conformal Fermi Coordinates is of the same order as that from the inflaton-curvaton interaction term but does not cancel it.https://resolver.caltech.edu/CaltechAUTHORS:20200629-093206924Quark model predictions for the electron energy spectrum in seileptonic D and B decays
https://resolver.caltech.edu/CaltechAUTHORS:20200928-162217927
Year: 2020
The constituent quark model is used to predict the electron
energy spectrum in semileptonic D and B meson decays. Particular attention is paid to the endpoint region of the electron spectrum in B decays since this is crucial to a determination of the b --> u weak mixing angle.https://resolver.caltech.edu/CaltechAUTHORS:20200928-162217927Observing the de Sitter Space Propagator
https://resolver.caltech.edu/CaltechAUTHORS:20200928-145738934
Year: 2020
The primordial fluctuations in the mass density may have arisen from quantum fluctuations in a scalar field that occurred during an inflationary era. Fluctuations which arose in this way can be highly non-Gaussian. Also the bad infrared properties of the propagator for a massless scalar field in de Sitter space can translate itself into a power spectrum, for the two-point spatial correlation of objects that do not trace the mass, which behaves like K^(-3), at small wavenumbers k.https://resolver.caltech.edu/CaltechAUTHORS:20200928-145738934Chiral perturbation theory and the delta I = 1/2 rule
https://resolver.caltech.edu/CaltechAUTHORS:20200928-170836480
Year: 2020
Chiral perturbation theory is applied to the decay K π 2π. It is shown that, to quadratic order-in meson masses, the amplitude for K → 2π can be written in terms of the unphysical amplitudes K + π and K + 0, where "0" is the vacuum. One may then hope to calculate these two simpler amplitudes with lattice Monte Carlo techniques, and thereby gain understanding of the ΔI = 1/2 rule in K decay. The reason for the presence of the K → 0 amplitude is explained: it serves to cancel off unwanted renormalization contributions to K + π. We make a rough rest of the practicability of these ideas to Monte Carlo studies. We also describe a method for evaluating meson decay constants which does not require a determination of the quark masses.https://resolver.caltech.edu/CaltechAUTHORS:20200928-170836480Weak radiative B meson decay
https://resolver.caltech.edu/CaltechAUTHORS:20200929-143446928
Year: 2020
Weak radiative B meson decays, Bγ -> γX_s have a B meson decaying to a hard photon (i.e., Eγ ≥ 2 GeV) and strange hadronic final states X_s. The prediction of the standard model (with minimal particle content) for the rate for this process is reviewed. Particular attention is paid to the role of strong interaction corrections, which have a significant impact on the rate.https://resolver.caltech.edu/CaltechAUTHORS:20200929-143446928Simple models with both baryon and lepton number violation by two units
https://resolver.caltech.edu/CaltechAUTHORS:20210412-105317827
Year: 2021
DOI: 10.1103/PhysRevD.104.015029
We construct simple renormalizable extensions of the standard model where the leading baryon number violating processes have ΔB = ±ΔL = −2. These models contain additional scalars. The simplest models contain a color singlet and a colored sextet. For such a baryon number violation to be observed in experiments, the scalars cannot be much heavier than a few tera-electron-volts. We find that such models are strongly constrained by LHC physics, LEP physics, and flavor physics.https://resolver.caltech.edu/CaltechAUTHORS:20210412-105317827Scalar leptoquarks, baryon number violation, and Pati-Salam symmetry
https://resolver.caltech.edu/CaltechAUTHORS:20210830-203807995
Year: 2021
DOI: 10.1103/PhysRevD.104.035017
One or more scalar leptoquarks with masses around a few TeV may provide a solution to some of the flavor anomalies that have been observed. We discuss the impact of such new degrees on baryon number violation when the theory is embedded in a Pati-Salam model. The Pati-Salam embedding can suppress renormalizable and dimension-five baryon number violation in some cases. Our work extends the results of Assad, Grinstein, and Fornal who considered the same issue for vector leptoquarks.https://resolver.caltech.edu/CaltechAUTHORS:20210830-203807995Radiative semileptonic B̅ decays
https://resolver.caltech.edu/CaltechAUTHORS:20211029-211331383
Year: 2022
DOI: 10.1007/JHEP02(2022)043
We consider the form factors for the radiative semileptonic decays B̅(v) → D(*)(v′)ℓν̅_ℓγ in the kinematic region where the photon momentum, k, is small enough that heavy quark symmetry (HQS) can be applied without the radiated photon changing the heavy quark velocity (i.e., v(′) ∙ k < m(b,c)). We find that HQS is remarkably powerful, leaving only four new undetermined form factors at leading order in 1/m(b,c). In addition, one of them is fixed in terms of the leading order Isgur-Wise function in the kinematic region, v(′) ∙ k < Λ_(QCD).https://resolver.caltech.edu/CaltechAUTHORS:20211029-211331383Regularization scheme dependence of the counterterms in the galaxy bias expansion
https://authors.library.caltech.edu/records/bqpes-nft23
Year: 2023
DOI: 10.1088/1475-7516/2023/11/087
<p>In this paper we explore how different regularization prescriptions affect the counterterms in the renormalization of the galaxy bias expansion. We work in the context of primordial local non-Gaussianity including non-linear gravitational evolution. We carry out the one-loop renormalization of the field δ²_ρ (i.e. the square of the matter overdensity field) up to third order in gravitational evolution. Three regularization schemes are considered and their impact on the values of the counterterms is studied. We explicitly verify that the coefficients of the non-boost invariant operators are regularization scheme independent.</p>https://authors.library.caltech.edu/records/bqpes-nft23Finite naturalness and quark-lepton unification
https://authors.library.caltech.edu/records/mwnes-9t882
Year: 2024
DOI: 10.1103/physrevd.109.015011
<p>We study the implications of finite naturalness in Pati-Salam models where SU(3)<em>꜀</em> is embedded in SU(4). For the minimal realization at low scale of quark-lepton unification, which employs the inverse seesaw for neutrino masses, we find that radiative corrections to the Higgs boson mass are at least <em>δmℎ²</em>/<em>mℎ² </em>~ <em>O</em>(10⁴). The one-loop contributions to the Higgs mass are suppressed by four powers of the hypercharge gauge coupling. We find that for the vector leptoquarks the naively leading part of the two-loop corrections cancel. We assume the Dirac Yukawa couplings for neutrinos are equal to the up-type quark Yukawa couplings as predicted in the minimal theory for quark-lepton unification. Despite these findings, the two-loop corrections still dominate the finite naturalness bound. We mention a way to relax the lower bound on the vector leptoquark mass and have <em>δmℎ</em>²/<em>mℎ</em>²<em> </em>~ <em>O</em>(10<em>²</em>).</p>https://authors.library.caltech.edu/records/mwnes-9t882Remembering Steven Weinberg and his research
https://authors.library.caltech.edu/records/h2fyw-a5z09
Year: 2024
DOI: 10.1016/j.nuclphysb.2024.116515
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<p>A brief discussion of my interactions with Steven Weinberg and the impact of his research and those interactions on my own work.</p>
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<ul class="issue-navigation u-margin-s-bottom u-bg-grey1"></ul>https://authors.library.caltech.edu/records/h2fyw-a5z09Atomic binding corrections for high-energy fixed target experiments
https://authors.library.caltech.edu/records/3bgpj-2w260
Year: 2024
DOI: 10.1103/physrevd.110.056032
<p>High-energy beams incident on a fixed target may scatter against atomic electrons. To a first approximation, one can treat these electrons as free and at rest. For precision experiments, however, it is important to be able to estimate the size of, and when necessary calculate, subleading corrections. We discuss atomic binding corrections to relativistic lepton-electron scattering. We analyze hydrogen in detail, before generalizing our analysis to multi-electron atoms. Using the virial theorem, and many-body sum rules, we find that the corrections can be reduced to measured binding energies, and the expectation value of a single one-body operator. We comment on the phenomenological impact for neutrino flux normalization and an extraction of hadronic vacuum polarization from elastic muon electron scattering at MUonE.</p>https://authors.library.caltech.edu/records/3bgpj-2w260