[ { "id": "authors:sgzeg-9zn05", "collection": "authors", "collection_id": "sgzeg-9zn05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120815-090132853", "type": "article", "title": "Early Work on the Positron and Muon", "author": [ { "family_name": "Anderson", "given_name": "C. D.", "clpid": "Anderson-C-D" } ], "abstract": "Early work on the positron and muon is described in an informal way, with emphasis on those aspects of the work which normally would not find their way into the literature.", "doi": "10.1119/1.1937627", "issn": "0002-9505", "publisher": "American Association of Physics Teachers", "publication": "American Journal of Physics", "publication_date": "1961-12", "series_number": "12", "volume": "29", "issue": "12", "pages": "825-830" }, { "id": "authors:vs3jx-n8260", "collection": "authors", "collection_id": "vs3jx-n8260", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141105-105453141", "type": "article", "title": "Cloud Chamber Investigation of Anomalous \u03b8^0 Particles", "author": [ { "family_name": "Kadyk", "given_name": "J. A.", "clpid": "Kadyk-J-A" }, { "family_name": "Trilling", "given_name": "G. H.", "clpid": "Trilling-G-H" }, { "family_name": "Leighton", "given_name": "R. B.", "clpid": "Leighton-R-B" }, { "family_name": "Anderson", "given_name": "C. D.", "clpid": "Anderson-C-D" } ], "abstract": "Eighteen anomalous \u03b8^0, (\u03b8^0_(anom)), decay events observed in the California Institute of Technology magnet cloud chambers have been analyzed. Many of these decays are dynamically inconsistent with the \u03c4^0\u2192\u03c0^++\u03c0^\u2212+\u03c0^0 scheme, but most are consistent with the decay processes: \u03b8^0_(anom)\u2192\u03c0^++\u03c0^\u2212+\u03b3, \u03c0^\u00b1+\u03bc^\u2213+\u03bd, and \u03c0^\u00b1+e^\u2213+\u03bd. However, at least one event is inconsistent with each decay scheme. From the locations of the decays in the cloud chamber, the lifetime is found to be significantly longer than that of the normal \u03b8^0 particle, called here the \u03b8^0_(\u03c02) particle. Other differences in the behavior of the \u03b80anom and \u03b8^0_(\u03c02) particles were also observed in the (a) momentum distributions, (b) origin locations, (c) relative numbers of \u03b8^0_(anom) and \u03b8^0_(\u03c02) particles traveling upward, and (d) the types of V particles produced in association with the \u03b8^0_(anom) and \u03b8^0_(\u03c02). It is concluded that not all the \u03b8^0_(anom) decays can result from alternate decay modes of the \u03b8^0_(\u03c02). Moreover, many decays can be neither \u03c4^0 decays nor alternate decays of the \u03b8^0_(\u03c02).\n\nThe characteristics of the \u03b8^0_2 particle proposed by Gell-Mann and Pais are consistent with those of the \u03b8^0_(anom) particle, with the possible exception of the observed types of associations. An estimate was made of the relative number of \u03b8^0_(anom) to \u03b8^0_(\u03c02) particles observed to decay in the cloud chamber. If all \u03b8^0_(anom) decays are assumed to arise from decays of the \u03b8^0_2 particle, then a lower limit for the \u03b8^0_2 lifetime is found to be about 10^(\u22129) sec.", "doi": "10.1103/PhysRev.105.1862", "issn": "0031-899X", "publisher": "American Physical Society", "publication": "Physical Review", "publication_date": "1957-03-15", "series_number": "6", "volume": "105", "issue": "6", "pages": "1862-1871" }, { "id": "authors:kf28a-1dv97", "collection": "authors", "collection_id": "kf28a-1dv97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:SORpr55a", "type": "article", "title": "Associated Production of \u039e- with Two \u03b80 Particles", "author": [ { "family_name": "Sorrels", "given_name": "J. D.", "clpid": "Sorrels-J-D" }, { "family_name": "Leighton", "given_name": "R. B.", "clpid": "Leighton-R-B" }, { "family_name": "Anderson", "given_name": "C. D.", "clpid": "Anderson-C-D" } ], "abstract": "A cosmic-ray event is described in which a negative cascade particle and two neutral heavy mesons appear to be produced in a single nuclear interaction above a cloud chamber. It is suggested that this event may be an example of the associated production of a \u039e- particle with two \u03b80 particles according to the scheme of Gell-Mann.", "doi": "10.1103/PhysRev.100.1457", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1955-12-01", "series_number": "5", "volume": "100", "issue": "5", "pages": "1457-1459" }, { "id": "authors:te1k0-af830", "collection": "authors", "collection_id": "te1k0-af830", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LINpr54b", "type": "article", "title": "Q Value of \u039b0 Decay", "author": [ { "family_name": "van Lint", "given_name": "V. A. J.", "clpid": "van-Lint-V-A-J" }, { "family_name": "Trilling", "given_name": "G. H.", "clpid": "Trilling-G-H" }, { "family_name": "Leighton", "given_name": "R. B.", "clpid": "Leighton-R-B" }, { "family_name": "Anderson", "given_name": "C. D.", "clpid": "Anderson-C-D" } ], "abstract": "Measurements of the energy release or Q value in \u039b0 decay have previously been reported [1]. From the photographs obtained in the 48-in. magnet cloud chambers now operating in Pasadena, a set of the most accurately measurable \u039b0 decays have been selected for calculations of Q values.", "doi": "10.1103/PhysRev.95.295", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1954-07-01", "series_number": "1", "volume": "95", "issue": "1", "pages": "295-296" }, { "id": "authors:7k2qc-3cv79", "collection": "authors", "collection_id": "7k2qc-3cv79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LINpr54a", "type": "article", "title": "Cloud-Chamber Observations of Some Unusual Neutral V Particles Having Light Secondaries", "author": [ { "family_name": "van Lint", "given_name": "V. A. J.", "clpid": "van-Lint-V-A-J" }, { "family_name": "Anderson", "given_name": "C. D.", "clpid": "Anderson-C-D" }, { "family_name": "Cowan", "given_name": "E. W.", "clpid": "Cowan-E-W" }, { "family_name": "Leighton", "given_name": "R. B.", "clpid": "Leighton-R-B" }, { "family_name": "York", "given_name": "C. M., Jr.", "clpid": "York-C-M-Jr" } ], "abstract": "From six cloud-chamber photographs of unusual V0 decay events, the following conclusions are drawn: (1) there is a neutral V particle that decays into two particles lighter than \u03ba mesons with a Q value too small to be consistent with a \u03b80(\u03c0, \u03c0, 214 Mev) particle; (2) some of these events cannot be explained in terms of the decay of a \u03c40(\u03c00, \u03c0-, \u03c0+, Q\u223c80 Mev) particle; (3) these events can be explained by any one of a number of three-body decay schemes, but two different types of V particles must be postulated if two-body decays are assumed.", "doi": "10.1103/PhysRev.94.1732", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1954-06-15", "series_number": "6", "volume": "94", "issue": "6", "pages": "1732-1735" }, { "id": "authors:6spjj-vzf33", "collection": "authors", "collection_id": "6spjj-vzf33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150811-123122633", "type": "article", "title": "Symbols for Fundamental Particles", "author": [ { "family_name": "Amaldi", "given_name": "E.", "clpid": "Amaldi-E" }, { "family_name": "Anderson", "given_name": "C. D.", "clpid": "Anderson-C-D" }, { "family_name": "Blackett", "given_name": "P. M. S.", "clpid": "Blackett-P-M-S" }, { "family_name": "Fretter", "given_name": "W. B.", "clpid": "Fretter-W-B" }, { "family_name": "Leprince-Ringuet", "given_name": "L.", "clpid": "Leprince-Ringuet-L" }, { "family_name": "Peters", "given_name": "B.", "clpid": "Peters-B" }, { "family_name": "Powell", "given_name": "C. F.", "clpid": "Powell-C-F" }, { "family_name": "Rochester", "given_name": "G. D.", "clpid": "Rochester-G-D" }, { "family_name": "Rossi", "given_name": "B.", "clpid": "Rossi-B" }, { "family_name": "Thompson", "given_name": "R. W.", "clpid": "Thompson-R-W" } ], "abstract": "IN recent years we have witnessed startling developments in the field of fundamental particles. One of the consequences has been the appearance in the scientific literature of a new jargon and of a large number of new symbols. Some symbols (such as \u03c0, \u00b5, \u03c4) designate specific kinds of particles. Others (such as \u03c1, \u03c3) have been used to describe merely a phenomenological behaviour. Various authors have called the same particle by different names or have attached different meanings to the same symbol. Sometimes the meaning of a symbol has changed through the years. To give an example, the Greek letter \u03c7 was used initially to describe a heavy meson which stops in the emulsion and afterwards decays, giving rise to a single ionizing particle. Later, the Latin letter K replaced the Greek letter \u03c7 as a code for the above phenomenological description, while the letter \u03c7 acquired a more definite physical meaning: that of a heavy meson which decays into one charged and two neutral particles. Sometimes, however, the letter K is also used to designate any charged particle, heavier than a \u03c0-meson and lighter than a proton, the mode of decay of which is unknown. As another example, the neutral particle of mass about 1,000 m e, which decays into two \u03c0-mesons, has been variously named v^0, V_2^0, V_4^0, whereas some authors have used the letter V_2^0 to designate any V^0-particle different from the so-called V_1^0.", "doi": "10.1038/173123a0", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "1954-01-16", "series_number": "4394", "volume": "173", "issue": "4394", "pages": "123-123" }, { "id": "authors:0kwje-cqy07", "collection": "authors", "collection_id": "0kwje-cqy07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LEIpr53", "type": "article", "title": "The decay of V0 particles", "author": [ { "family_name": "Leighton", "given_name": "R. B.", "clpid": "Leighton-R-B" }, { "family_name": "Wanlass", "given_name": "S. D.", "clpid": "Wanlass-S-D" }, { "family_name": "Anderson", "given_name": "C. D.", "clpid": "Anderson-C-D" } ], "abstract": "In a set of 23,000 cloud-chamber photographs taken in a study of penetrating showers, 134 examples of the decay of neutral V-particles, and 18 of the decay of charged V-particles, were observed. An analysis of the 152 examples leads to the following principal conclusions: (1) V-particles result from the impact of mesons and probably also of nucleons, upon nuclei. (2) V-particles are generally produced singly and not in pairs. (3) Two independent kinds of data, one based on measurements of angles and other purely spatial relationships, and the other based on measurements of momentum and specific ionization, lead to the conclusion that more than 80 percent of these neutral V-particles decayed by the production of a heavy positive and a light negative particle. The mass of the heavy positive particle in most instances was consistent with that of a proton, but in a few cases may have been somewhat less. The negative particle appeared most often to be a \u03c0-meson, although in a few cases a \u03bc-meson was indicated. In about 7 percent of the cases, the positive particle was light and had a mass consistent with that of a \u03c0- or \u03bc-meson. In these cases the mass of the negative particle was not well determined. So far, therefore, in these investigations, there is no direct evidence that a neutral V-particle decays into two \u03c0-mesons, or into a positive \u03c0-meson and a negatively charged proton, although a few cases may be so interpreted. (4) The data are consistent with the assumption of a two-body decay for a majority of the neutral V-particles, and therefore a rather extensive analysis is given based upon this assumption. (5) The energy release, or Q-value, of the decay of neutral V-particles was computed, on the assumption of a two-body decay, for those cases in which the production of a heavy positive particle was clearly indicated, and where momentum measurements were possible. On the assumption of a decay into a proton and a \u03c0- meson, the Q-values obtained ranged from 10 Mev to about 100 Mev. The great majority of cases however, may be described in terms of discrete Q-values at 35\u00b13 Mev, and 75\u00b15 Mev, although, of course, the data are consistent with distributions about these values. For the same set of cases, if the positive particle is assumed to be as light even as 1250me, and/or the negative particle is assumed to be a \u03bc-meson, the distribution of Q-values is not greatly changed, and the apparent necessity for at least two different Q-values remains. In those few cases mentioned in (3) above, in which the positive particle was light, and in which the mass of the negative particle was undetermined, the energy release, computed on the basis of a two-body decay, depends upon the assumed identity of the decay products, and is about 100-130 Mev for the assumption that two \u03c0-mesons are produced, about 50-80 Mev for a positive \u03c0-meson and a negative \u03c4-meson, and about 30-80 Mev for a positive \u03c0-meson and a negative proton. (6) The rest mean lifetime of V0 particles, which appear to yield protons and \u03c0--mesons as decay products, was found to be 1.6\u00d710-10 sec for 26 cases having Q-values greater than 50 Mev, and 2.9\u00d710-10 sec for 48 cases having Q-values less than 50 Mev, on the assumption of a two-body decay. In view of the rather poor statistics, the above two lifetimes are consistent with a single value, and lead to an average of 2.5\u00b10.7\u00d710-10 sec. The above lifetimes are not appreciably changed if a multibody decay of the neutral V-particle is assumed. (7) The data are not adequate to distinguish conclusively between a two-body and a multi-body decay, and, therefore, a discussion is also given in terms of a variety of possible decay schemes of the neutral V-particle.", "doi": "10.1103/PhysRev.89.148", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1953-01-01", "series_number": "1", "volume": "89", "issue": "1", "pages": "148-167" }, { "id": "authors:amq25-hw944", "collection": "authors", "collection_id": "amq25-hw944", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:SERpr50", "type": "article", "title": "Cloud-Chamber Observations of the New Unstable Cosmic-Ray Particles", "author": [ { "family_name": "Seriff", "given_name": "A. J.", "clpid": "Seriff-A-J" }, { "family_name": "Leighton", "given_name": "R. B.", "clpid": "Leighton-R-B" }, { "family_name": "Hsiao", "given_name": "C.", "clpid": "Hsiao-C" }, { "family_name": "Cowan", "given_name": "E. W.", "clpid": "Cowan-E-W" }, { "family_name": "Anderson", "given_name": "C. D.", "clpid": "Anderson-C-D" } ], "abstract": "Thirty-four \"forked tracks\" similar to two previously reported by Rochester and Butler have been observed in 11,000 cloud-chamber photographs of cosmic-ray penetrating showers, confirming their conclusion that new unstable neutral and charged particles exist. The lifetime of the neutral particles is found to be about 3\u00d710^-10 sec., and some information as to the nature of the decay products is given.", "doi": "10.1103/PhysRev.78.290", "issn": "0031-899X", "publisher": "American Physical Society", "publication": "Physical Review", "publication_date": "1950-05-01", "series_number": "3", "volume": "78", "issue": "3", "pages": "290-291" }, { "id": "authors:tqt73-yr243", "collection": "authors", "collection_id": "tqt73-yr243", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LEIpr49", "type": "article", "title": "The energy spectrum of the decay particles and the mass and spin of the mesotron", "author": [ { "family_name": "Leighton", "given_name": "Robert B.", "clpid": "Leighton-R-B" }, { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" }, { "family_name": "Seriff", "given_name": "Aaron J.", "clpid": "Seriff-A-J" } ], "abstract": "Energy values determined from curvature measurements of 75 cloud-chamber tracks of decay particles of cosmic-ray mesotrons at sea level, in a magnetic field of 7250 gauss, are here reported. The observed spectrum extends from 9 Mev to 55 Mev with an apparently continuous distribution of intermediate energy values and a mean energy of 34 Mev. The shape of the spectrum and the value of its upper limit are strong evidence that the mesotron disintegrates into an electron and two neutrinos. It is concluded that the mesotron has half-integral spin. The value of the observed upper limit of the energy spectrum corresponds to a mass value of the mesotron equal to 217\u00b14 electron masses.", "doi": "10.1103/PhysRev.75.1432", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1949-05-01", "series_number": "9", "volume": "75", "issue": "9", "pages": "1432-1437" }, { "id": "authors:g0g8w-y8n85", "collection": "authors", "collection_id": "g0g8w-y8n85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ADArmp49", "type": "article", "title": "Observations of cosmic rays at high altitudes", "author": [ { "family_name": "Adams", "given_name": "Raymond V.", "clpid": "Adams-R-V" }, { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" }, { "family_name": "Cowan", "given_name": "Eugene W.", "clpid": "Cowan-E-W" } ], "abstract": "Direct measurements of the momenta of cosmic-ray particles at an altitude of 30,000 feet have recently been reported.", "doi": "10.1103/RevModPhys.21.72", "issn": "0034-6861", "publisher": "Reviews of Modern Physics", "publication": "Reviews of Modern Physics", "publication_date": "1949-01-01", "series_number": "1", "volume": "21", "issue": "1", "pages": "72-75" }, { "id": "authors:3dbw2-6bz48", "collection": "authors", "collection_id": "3dbw2-6bz48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ADArmp48", "type": "article", "title": "Cosmic rays at 30,000 feet", "author": [ { "family_name": "Adams", "given_name": "Raymond V.", "clpid": "Adams-R-V" }, { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" }, { "family_name": "Lloyd", "given_name": "Paul E.", "clpid": "Lloyd-P-E" }, { "family_name": "Rau", "given_name": "R. Ronald", "clpid": "Rau-R-R" }, { "family_name": "Saxena", "given_name": "Ram C.", "clpid": "Saxena-R-C" } ], "abstract": "A discussion is given of the data obtained in a recent series of flights of a B-29 airplane at altitudes up to 40,000 ft., in which a cloud chamber, actuated by Geiger counters, was operated in a magnetic field of 7500 gauss. The frequency of occurrence of single particles and electron showers at elevations of 800 ft., 14,100 ft., and 30,000 ft. is compared. Examples of heavily ionizing particles and of nuclear disintegrations are discussed. Direct measurements of the energies of cosmic-ray particles at 30,000 ft. are compared with similar measurements made at sea level. These measurements indicate that up to one-third of the particles which occur singly in the chamber, in the momentum range up to 107 gauss-cm, may consist of protons and the remainder of mesotrons, in contrast to sea level observations which show that protons are there present in only negligible numbers.", "doi": "10.1103/revmodphys.20.334", "issn": "0034-6861", "publisher": "Reviews of Modern Physics", "publication": "Reviews of Modern Physics", "publication_date": "1948-01", "series_number": "1", "volume": "20", "issue": "1", "pages": "334-349" }, { "id": "authors:1khyb-fd742", "collection": "authors", "collection_id": "1khyb-fd742", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANDpr47", "type": "article", "title": "On the mass and the disintegration products of the mesotron", "author": [ { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" }, { "family_name": "Adams", "given_name": "Raymond V.", "clpid": "Adams-R-V" }, { "family_name": "Lloyd", "given_name": "Paul E.", "clpid": "Lloyd-P-E" }, { "family_name": "Rau", "given_name": "R. Ronald", "clpid": "Rau-R-R" } ], "abstract": "A photograph has been obtained of a mesotron of positive charge which comes to rest in the gas of a cloud chamber and ejects a positron of 24-Mev energy. Several possible interpretations of this photograph are discussed.", "doi": "10.1103/PhysRev.72.724", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1947-10-15", "series_number": "8", "volume": "72", "issue": "8", "pages": "724-727" }, { "id": "authors:07wxh-tqq76", "collection": "authors", "collection_id": "07wxh-tqq76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:NEDpr39", "type": "article", "title": "Composition of Cosmic Rays. III. Nature of cosmic-ray particles", "author": [ { "family_name": "Neddermeyer", "given_name": "Seth H.", "clpid": "Neddermeyer-S-H" }, { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" } ], "abstract": "The first section of this report contains a brief summary of those experiments which have made substantial contributions to our knowledge of the nature and mode of absorption of cosmic-ray particles. Included is a discussion of the difficulties which inhere in the attempts to interpret the observed cosmic-ray phenomena in terms of the assumption that the cosmic-ray particles are practically all protons and positive and negative electrons. These difficulties are resolved by demonstrating that in the same momentum range there exist two types of particles, one of which is highly absorbed in a heavy material, mostly through radiation, while the other is relatively penetrating. Behavior of the first kind is typical of shower particles in general, and of all single negatron secondaries, which are presumably produced in elastic collisions with atomic electrons. This group is therefore to be identified with electrons. As it can be shown that particles of the penetrating group cannot be of protonic mass, it follows that they must be neither electrons nor protons. The simplest assumption is that their distinguishing property is a mass intermediate between the electron and proton. Confirmation of this view is found in the observation by other writers and by ourselves of particles whose range, ionization and curvature relations are such that they demand a mass in this region. The best range and ionization data seem to give mass determinations in the neighborhood of 200 electron masses. A discussion is given of certain difficulties which exist in the interpretation of cosmic-ray particles as electrons and mesotrons of a unique mass.", "doi": "10.1103/RevModPhys.11.191", "issn": "0034-6861", "publisher": "Reviews of Modern Physics", "publication": "Reviews of Modern Physics", "publication_date": "1939-07-01", "series_number": "3-4", "volume": "11", "issue": "3-4", "pages": "191-207" }, { "id": "authors:k2dqr-44358", "collection": "authors", "collection_id": "k2dqr-44358", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:NEDpr38", "type": "article", "title": "Cosmic-ray particles of intermediate mass", "author": [ { "family_name": "Neddermeyer", "given_name": "Seth H.", "clpid": "Neddermeyer-S-H" }, { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" } ], "abstract": "A Geiger-counter placed inside a cloud chamber and coupled by means of a coincidence circuit to a second counter placed above the chamber has been employed to increase the probability of observing cosmic-ray particles near the ends of their ranges, and thus to provide information concerning the mass and stability properties of the particles of intermediate mass.", "doi": "10.1103/PhysRev.54.88.2", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1938-07-01", "series_number": "1", "volume": "54", "issue": "1", "pages": "88-89" }, { "id": "authors:45wxv-rfz74", "collection": "authors", "collection_id": "45wxv-rfz74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:NEDpr37", "type": "article", "title": "Note on the nature of cosmic-ray particles", "author": [ { "family_name": "Neddermeyer", "given_name": "Seth H.", "clpid": "Neddermeyer-S-H" }, { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" } ], "abstract": "Measurements (1) of the energy loss of particles occurring in the cosmic-ray showers have shown that this loss is proportional to the incident energy and within the range of\nthe measurements, up to about 400 Mev, is in approximate agreement with values calculated theoretically for electrons by Bethe and Heitler. These measurements were taken using a thin plate of lead (0.35 cm), and the observed individual losses were found to vary from an amount below experimental detection up to the whole initial energy of the particle, with a mean fractional loss of about 0.5.", "doi": "10.1103/PhysRev.51.884", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1937-05-15", "series_number": "10", "volume": "51", "issue": "10", "pages": "884-886" }, { "id": "authors:kdeta-qmz63", "collection": "authors", "collection_id": "kdeta-qmz63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANDpr36", "type": "article", "title": "Cloud chamber observations of cosmic rays at 4300 meters elevation and near sea-level", "author": [ { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" }, { "family_name": "Neddermeyer", "given_name": "Seth H.", "clpid": "Neddermeyer-S-H" } ], "abstract": "Cloud chamber photographs at 4300 meters elevation show positive and negative electron tracks similar to those observed at sea-level, but positive-negative electron showers occur more frequently and, in general, consist of more numerous tracks. Showers of 2-4 tracks, 5-10 tracks, and 11-100 tracks occur respectively, 8.6, 21 and 29 times as frequently per unit time at 4300 meters as they do near sea-level. Further measurements on the energy loss in lead of electrons up to 400 MEV, are given. They show that in this range of energies the energy loss in lead is roughly proportional to the incident energy. About one percent of the exposures on Pike's Peak reveal the presence of strongly ionizing particles which in most cases seem to be protons. The proportion of such tracks is considerably greater than at Pasadena. These heavy tracks in general bear only little relation in direction to that of the incoming beam, and usually arise from a type of nuclear disintegration not heretofore observed. The energies of these heavily ionizing particles may rise to values so high as 150 MEV, thus indicating that the source of the particle energies is in the cosmic rays.", "doi": "10.1103/PhysRev.50.263", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1936-08-15", "series_number": "4", "volume": "50", "issue": "4", "pages": "263-271" }, { "id": "authors:5aj7g-7tb45", "collection": "authors", "collection_id": "5aj7g-7tb45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANDpr34b", "type": "article", "title": "The relation of the positron energy spectrum to the decay constant and to the energy of the bombarding protons", "author": [ { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" }, { "family_name": "Neddermeyer", "given_name": "Seth H.", "clpid": "Neddermeyer-S-H" } ], "abstract": "We have reported(1) approximate energy distributions of the positrons emitted by various substances activated by proton or deuton bombardment. A typical photograph is reproduced in Fig. 1. To find whether a relation exists between the maximum energy of the bombarding particles and the energies of the disintegration positrons we have studied numerous samples of carbon bombarded by protons at peak voltages of 900,000 and 700,000, supplied us by Dr. Lauritsen and Mr. Crane.", "doi": "10.1103/PhysRev.45.653", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1934-05-01", "series_number": "9", "volume": "45", "issue": "9", "pages": "653-654" }, { "id": "authors:qbvyh-br102", "collection": "authors", "collection_id": "qbvyh-br102", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:NEDpr34", "type": "article", "title": "Energy spectra of positrons ejected by artificially stimulated radioactive substances", "author": [ { "family_name": "Neddermeyer", "given_name": "Seth H.", "clpid": "Neddermeyer-S-H" }, { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" } ], "abstract": "Curie and Joliot (1) have reported that under the bombardment by \u03b1-particles from Po, several of the light elements, viz., B, Mg, Al undergo transmutations which result in the production of radioactive isotopes which have half-lives of the order of several minutes and disintegrate by the ejection of positrons.", "doi": "10.1103/PhysRev.45.498", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1934-04-01", "series_number": "7", "volume": "45", "issue": "7", "pages": "498-499" }, { "id": "authors:s098j-2m822", "collection": "authors", "collection_id": "s098j-2m822", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANDpr34a", "type": "article", "title": "The Mechanism of Cosmic-Ray Counter Action", "author": [ { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" }, { "family_name": "Millikan", "given_name": "R. A.", "clpid": "Millikan-R-A" }, { "family_name": "Neddermeyer", "given_name": "Seth", "clpid": "Neddermeyer-S-H" }, { "family_name": "Pickering", "given_name": "William", "clpid": "Pickering-W-H" } ], "abstract": "A study of photographs taken in a very powerful magnetic field with the aid of a cloud chamber activated by counter responses shows (1) that such an arrangement has a strong selective action on showers; (2) that showers so selected have an exceptional multiplicity of tracks; (3) that the two counters show simultaneous responses when no single particle can pass through both of them; (4) that in general these showers consist of a mixture of positive and negative electrons rather than of electrons and protons, no effects certainly attributable to neutrons being observed; (5) that these electrons in getting out of the nucleus some times produce an intense photon spray of the nature of \"brems strahlung\"; (6) that these photon sprays are increasingly responsible for the simultaneous activation of the two counters the thicker the intervening lead; (7) that a light element like carbon has little effect in producing either showers or sprays; (8) that the total energy of a shower is not larger than that of single electrons (+ or -); (9) that the Dirac theory encounters certain difficulties in accounting for the observed effects.", "doi": "10.1103/PhysRev.45.352", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1934-03-15", "series_number": "6", "volume": "45", "issue": "6", "pages": "352-363" }, { "id": "authors:azkcz-4jj90", "collection": "authors", "collection_id": "azkcz-4jj90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MILpr34", "type": "article", "title": "The three types of cosmic-ray fluctuations and their significance", "author": [ { "family_name": "Millikan", "given_name": "Robert A.", "clpid": "Millikan-R-A" }, { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" }, { "family_name": "Neher", "given_name": "H. Victor", "clpid": "Neher-H-V" } ], "abstract": "A theory of cosmic-ray bursts is advanced with which the energy released in them is assumed to come not from the cosmic-rays themselves but from the battery which charges the electroscope. These bursts then represent, according to this theory, instrumental accidents which must be eliminated before the remaining fluctuations can be interpreted. The discovery that the remainder of the ionization observed in a cosmic-ray electroscope is due wholly to positrons and negatrons shooting through the chamber makes it possible to compute the fluctuations to be expected from a random distribution of these electron shots. The observed fluctuations, after the elimination of bursts, are found to be somewhat larger than the fluctuations thus computed. From the amount of this excess the percentage of cosmic-ray \"showers\" (two or more associated tracks) can be computed and is found by Evans and Neher to be in general agreement with the number directly observed in cloud-chamber experiments.", "doi": "10.1103/PhysRev.45.141", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1934-02-01", "series_number": "3", "volume": "45", "issue": "3", "pages": "141-143" }, { "id": "authors:y7bw6-vtt26", "collection": "authors", "collection_id": "y7bw6-vtt26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141105-125037293", "type": "article", "title": "Cosmic-Ray Positive and Negative Electrons", "author": [ { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" } ], "abstract": "A determination of the specific ionization of cosmic-ray particles, first, by a count of the number of drops per cm along cosmic-ray tracks on cloud-chamber photographs and, second, by measurements of the energy loss in lead has shown that the great bulk of the cosmic-ray particles of positive charge are positive electrons. The primary ionization was found to be about 31 ion-pairs per cm in air at S.T.P., but the total energy loss represents about 120 ion pairs per cm in air. Approximately the same values of specific ionization were found for the positives as for the negatives. Positive and negative electrons were found to occur in nearly equal numbers and to have similar distributions in energy. Energy distribution curves are given for the positives and negatives. A brief description of the experimental procedure is given, and several track photographs are shown. In view of the discovery that hard gamma-rays of Th C\u2032\u2032 give rise to positives and negatives in pairs, similar to the effects found in cosmic-ray studies, it is concluded that the absorption of the Th C\u2032\u2032 rays is due in part to that by free negative electrons and in part to a nuclear effect which results in the production of pairs of positive and negative electrons, the former effect accounting for the greater part of the absorption of the Th C\u2032\u2032 rays. The symmetry in occurrence of the positive and negative electrons found in the cosmic-ray studies shows that the nuclear effect which results in the production of positive and negative electrons in pairs represents the predominant part of the absorption for the range of energies as high as those of the cosmic rays and that the absorption by free negative electrons is relatively small.", "doi": "10.1103/PhysRev.44.406", "issn": "0031-899X", "publisher": "American Physical Society", "publication": "Physical Review", "publication_date": "1933-09-01", "series_number": "5", "volume": "44", "issue": "5", "pages": "406-416" }, { "id": "authors:afqs0-2f068", "collection": "authors", "collection_id": "afqs0-2f068", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANDpr33c", "type": "article", "title": "Positrons from gamma-rays", "author": [ { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" }, { "family_name": "Neddermeyer", "given_name": "Seth H.", "clpid": "Neddermeyer-S-H" } ], "abstract": "A report of the direct observation of positrons ejected from lead by hard gamma-rays has been published.(1) A source of radiothorium with its disintegration products was used. To obtain a well-defined beam the gamma-rays were collimated by allowing them to pass through a half-inch hole in a series of lead blocks totaling 18 inches in length. That the beam actually was well defined is shown by the fact that most of the observed tracks appeared to originate within a rather narrow region, about 3 cm wide. In this series of photographs the beam passed vertically downward through the side wall of a Wilson chamber across which were placed a 2 mm lead sheet, and below this a 0.5 mm sheet of aluminum. A magnetic field of 430 gauss normal to the face of the chamber and uniform to within 10 percent was used.", "doi": "10.1103/PhysRev.43.1034", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1933-06-15", "series_number": "12", "volume": "43", "issue": "12", "pages": "1034" }, { "id": "authors:3cqmp-9q965", "collection": "authors", "collection_id": "3cqmp-9q965", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANDpr33b", "type": "article", "title": "The positive electron", "author": [ { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" } ], "abstract": "Out of a group of 1300 photographs of cosmic-ray tracks in a vertical Wilson chamber 15 tracks were of positive particles which could not have a mass as great as that of the proton. From an examination of the energy-loss and ionization produced it is concluded that the charge is less than twice, and is probably exactly equal to, that of the proton. If these particles carry unit positive charge the curvatures and ionizations produced require the mass to be less than twenty times the electron mass. These particles will be called positrons. Because they occur in groups associated with other tracks it is concluded that they must be secondary particles ejected from atomic nuclei.", "doi": "10.1103/PhysRev.43.491", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1933-03-15", "series_number": "6", "volume": "43", "issue": "6", "pages": "491-494" }, { "id": "authors:3xjeq-jqx03", "collection": "authors", "collection_id": "3xjeq-jqx03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANDpr33a", "type": "article", "title": "Cosmic-ray bursts", "author": [ { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" } ], "abstract": "In cloud-chamber experiments the frequent occurrence of associated tracks has been observed.(1) It has been pointed out that a simple binary collision cannot explain all the associated tracks.(2)", "doi": "10.1103/PhysRev.43.368", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1933-03-01", "series_number": "5", "volume": "43", "issue": "5", "pages": "368-369" }, { "id": "authors:44qws-yk633", "collection": "authors", "collection_id": "44qws-yk633", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANDpr32", "type": "article", "title": "Energies of Cosmic-Ray Particles", "author": [ { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" } ], "abstract": "Cloud chamber photographs of cosmic-ray tracks in a magnetic field up to 17,000 gauss are shown. On the assumption that the particles producing the tracks are travelling downward through the chamber rather than upward, particles of positive charge appear as well as electrons. From the specific ionization along the track it is concluded that the positives are protons, and are not nuclei of charge greater than unity. No evidence is uncovered demanding the introduction of a neutron for cosmic-ray phenomena. Eight examples of associated tracks are shown. Energies range from below 10^6 electron-volts to values in a few cases of the order of 10^9 electron-volts. Energy values for 70 tracks are listed. The scattering of cosmic particles in traversing a 6.0 mm lead plate is measured.", "doi": "10.1103/PhysRev.41.405", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1932-08-15", "series_number": "4", "volume": "41", "issue": "4", "pages": "405-434" }, { "id": "authors:84wj2-t0x81", "collection": "authors", "collection_id": "84wj2-t0x81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MILpr32a", "type": "article", "title": "Cosmic-ray energies and their bearing on the photon and neutron hypotheses", "author": [ { "family_name": "Millikan", "given_name": "Robert A.", "clpid": "Millikan-R-A" }, { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" } ], "abstract": "ON NOVEMBER 20, 1931, in a lecture before a large audience gathered at the Institut Poincar\u00e9 in Paris, there were presented the first direct measurements taken by Carl D. Anderson of the energies of cosmic-ray tracks made with an apparatus capable of measuring, by the method of magnetic deflectibility in air, energies of the order of magnitude to be expected in cosmic-ray photon-encounters with electrons and nuclei, namely, from 27\u00d710^(6) volts up to at least 500\u00d710^(6) volts. These same photographs were also shown on November 23rd at a physical seminar at the Cavendish Laboratories. Cambridge, England. The eleven cosmic-ray-track photographs shown and discussed on these occasions1 brought to light a certain number of new and important facts presented essentially as listed below in both of these lectures, and these facts have now been checked by three times as many successful exposures.", "doi": "10.1103/PhysRev.40.325", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1932-05-01", "series_number": "3", "volume": "40", "issue": "3", "pages": "325-328" }, { "id": "authors:v8qs8-5ez10", "collection": "authors", "collection_id": "v8qs8-5ez10", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANDpr30", "type": "article", "title": "Space-distribution of x-ray photoelectrons ejected from the K and L atomic energy-levels", "author": [ { "family_name": "Anderson", "given_name": "Carl D.", "clpid": "Anderson-C-D" } ], "abstract": "A C.T.R. Wilson expansion-chamber was used to study the space-distribution of photoelectrons ejected from a gas by monochromatic x-rays. In agreement with Auger, and Watson and Van den Akker a more isotropic space-distribution was found for electrons ejected from the L energy-levels than for those ejected from the K energy-level. The distribution of the electrons from the L energy-levels became less isotropic with an increase in frequency of the incident radiation. For a given radiation, the average forward momentum of the electrons from the K energy-level was found to decrease with an increase in the binding energy of the parent atom. Within experimental error, however, for electrons from the K energy level, even for different binding energies, the average forward momentum remained the same for a given velocity of ejection of the electron. The average forward momentum of electrons from the L energy-level was greater than that for electrons from the K energy-level for a given velocity of ejection. The space-distribution of electrons from the K energy-level was in fair accord with the recent results of quantum mechanics.", "doi": "10.1103/PhysRev.35.1139", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1930-05-15", "series_number": "10", "volume": "35", "issue": "10", "pages": "1139-1145" } ]