Showing papers on "Elementary particle published in 1975"

Infrared Singularities and Massive Fields

Abstract: We examine some problems associated with the low-momentum behavior of gauge theories and other renormalizable field theories. Our main interest is in the infrared structure of unbroken non-Abelian gauge theories and how this is affected by the presence of other heavy fields coupled to the massless gauge fields. It is shown in the context of a simple model of gauge mesons coupled to massive fermions that the heavy fields decouple at low momenta except for their contribution to renormalization effects. This result is used to discuss the mass-shell structure of the fermion propagator. The decoupling theorem is then stated for a general renormalizable theory and applied to some interesting examples. One is a more general gauge theory which makes use of the Higgs mechanism and attempts to unify the elementary particle forces. Another is the connection of the linear and nonlinear $\ensuremath{\sigma}$ models in the limit ${m}_{\ensuremath{\sigma}}\ensuremath{\rightarrow}\ensuremath{\infty}$.

Semiclassical bound states in an asymptotically free theory

Abstract: A semiclassical calculation of the particle spectrum in the Gross--Neveu model was carried out. It is a two-dimensional model with N species of fermions interacting through a symmetrical scalar-scalar interaction and is renormalizable, asymptotically free, and exhibits spontaneous symmetry breaking. A rich spectrum of particles is found which can be interpreted as fermion- antifermion bound states and multifermion bound states. These states fall into supermultiplets whose origin one does not completely understand. The binding mechanism is a vacuum-polarization effect rather than the direct interaction between particles. A general method for handling fermions in semiclassical calculations is developed. (auth)

Quantization of nonlinear waves

Abstract: We suggest that certain nonlinear field theories possess a particle spectrum, richer than has been heretofore discussed. In addition to states associated with quantization of the free-field modes of oscillation---these are the conventional particles of the theory---there also appear heavy particles, which carry a new quantum number and are stable. An approximation scheme is developed in which the signal for these new particles is the existence of stable static solutions with finite energy to the classical equations of motion. We give a systematic expansion for the theory, with special emphasis on the translational motion.

The Particle Data Group: Growth and Operations-Eighteen Years of Particle Physics

Abstract: A review is given of the growth of particle physics data as it relates to the collection, evaluation, correction, verification, analysis, and distribution by the Particle Data Group. (SDF)

Elementary particles in a curved space. IV. Massless particles

Abstract: If physics is stable with respect to a class of perturbations of the spacetime metric, including that of "small" constant four-dimensional curvature, then it may be shown that (1) left-handed and right-handed neutrinos are distinguished by a superselection rule; (2) magnetic monopoles cannot exist; (3) the conformal symmetry associated with the field equations for massless particles with spin 0, \textonehalf{}, and 1 is spontaneously broken\char22{}except in the case of neutrinos with fixed chirality.

Evidence for the temporary existence of a “composite” system in deep inelastic nuclear interactions

Abstract: Masses and charges have been identified for the light fragments (6

An attempt to resolve the astrophysical puzzles by postulating scale degree of freedom

Abstract: If we assume that scale is a degree of freedom which a physical object, such as a galaxy possesses besides translational and rotational degrees of freedom, we are able to incorporate such diverse phenomena as the systematic cosmological red-shifts, anomalous red-shifts, controversals of quasars, and the expansion of Earth into a single theory. At the same time we can consider the proposed existence of active dilatation as a physical realization of conformal transformations. Active conformal transformations transform the rest masses of particles. The objection that this implies a continuous rest mass spectrum which is not observed is avoided by assuming that particles can form bound systems such as nuclei, atoms, crystals, galaxies, etc., only if ‘discrete’ scale relations are established among the constituent particles. Different galaxies can be dilated relative to each other. (Note the analogy with ‘discrete’ positions of atoms in a crystal. Different crystals can be translated arbitrarily each to the other.) An observer in a contracting galaxy experiences that the universe is expanding.

The Solvay Conferences on Physics: Aspects of the Development of Physics Since 1911

Abstract: 1 Ernest Solvay and the Origin of Solvay Conferences on Physics.- 2 Radiation Theory and the Quanta.- 3 The Structure of Matter.- 4 Atoms and Electrons.- 5 The Electrical Conductivity of Metals.- 6 Electrons and Photons.- 7 Magnetism.- 8 The Structure and Properties of Atomic Nuclei.- 9 Towards the Spectrum of Elementary Particles and the Hierarchy of Interactions.- 10 The Elementary Particles.- 11 Quantum Field Theory.- 12 Fundamental Problems in Elementary Particle Physics.- 13 Symmetry Properties of Nuclei.- 14 Solid State Physics.- 15 Astrophysics, Gravitation, and the Structure of the Universe.- Index of Names.

Mass relations for charmed baryons

Abstract: A minimal-symmetry quark model for baryons is extended by charmed-quark substitution to charmed baryons. This induces a transformation of 9 mass relations for the 18 uncharmed baryons directly into 14 mass relations for 22 charmed baryons, with minimal SU(4) or SU(8) symmetry assumptions. Of the charmedbaryon mass relations, 6 are for mass differences of electromagnetic order and 8 are for strong mass differences.

Light as a fundamental particle

Abstract: We take it pretty much for granted that the whole visible world of matter and radiation can be explained, if not in fact at least in principle, in terms of the interactions of a handful of so‐called “elementary particles”: the electron; the proton; the neutron; the quantum of light, the photon; the quantum of gravitational radiation, the graviton, and perhaps also the neutrino. We would like to know why these particles have the properties they have, and therefore why the world is the way it is. Or, if you do not believe that scientists should ask “why,” you can restate the question in this form: What we want to know is the set of simple principles from which the properties of these particles, and hence everything else, can be deduced.

Search for selectivity in interactions of chiral solvated electrons.

Abstract: ULBRICHT'S suggestion1 that naturally occurring dissymmetry at the elementary particle level may be responsible for the chirality of molecules in the biosphere has feeen subjected to laboratory tests using polarised electrons2,3 and muons4. Some positive results are claimed to result from β− and β+ radiations2,3. Garay found a higher radiation yield for the decomposition of D-tyrosine than for L-tyrosine when subjected to intrinsically ‘left-handed’ β− particles from 90Sr in dilute aqueous solution. Since 2.26-MeV β− particles each create ∼ 105 secondary electrons during their energy degradation, the direct chemical consequences of the primary particle itself should be trivial. This suggests that dissymmetry must be transmitted through secondary chemical reactions. In the positron and muon experiments the ultimate fate of the individual polarised particles were studied in pure crystalline chiral media and in these cases the particle eventually abstracts an electron from the medium, principally while it is still epithermal.

Exchange Symmetry of the Effective Interaction in the Landau-Migdal Theory of Finite Fermi Systems

Abstract: We investigate the particle exchange symmetry of the phenomenological effective particle-hole interaction used in the theory of Finite Fermi Systems. We find that experimental data and consistency relations support an interaction which is antisymmetric at the surface and in the exterior region of the nucleus and nonsymmetric in the interior. Besides, we show that the number of adjustable parameters of the effective interaction can be reduced substantially by the use of generalized Ward identities without any loss of agreement with experimental data.

An investigation of the L 2 - L 3 Coster-Kronig transition probability for 63≦ Z≦96

Abstract: The total transition probabilityf 23 for theL 2-L 3 Coster-Kronig transition probability atZ=80, 81, 82, and 92 was measured withL α x-ray coincidences between high resolution Si(Li) and Ge(HP) x-ray detectors and a dual-parameter multichannel coincidence system. TheL α gating technique for observing theK x-ray coincidence spectrum was carefully checked and found to be equivalent to the method of observing theL x-ray spectrum with $$K_{\alpha _{1,2} } $$ gates, when proper corrections are applied. The values off 23 found are 0.123±0.012, 0.109±0.011, 0.105±0.011, and 0.146±0.018 atZ=80, 81, 82, and 92, respectively. These values, together with all previously published values in the region 57≦Z≦96, are critically evaluated and a group of “best values” selected for comparison with theory. The agreement is quite good in the region 63≦Z≦83. The independentparticle model employing a Green-Sellin-Zachor potential used by Chen and Crasemann predicts values off 23 which are too large compared with experiment in the high-Z region, whereas the theoretical predictions of McGuire using an approximate Herman-Skilman potential are too low. However, the screened nonrelativistic hydrogenic results of Chen, Crasemann, and Kostroun are in satisfactory agreement with the experiments. The experimental result atZ=92 indicates that theL 2-L 3 M 4 transition is at or below threshold and contributes little or no intensity to the value of f23.

Bremsstrahlung in a nonequilibrium plasma

Abstract: In an analysis of bremsstrahlung in a nonequilibrium plasma it is shown that in a plasma, in contrast with vacuum, there are two types of bremsstrahlung, which result from the transformation of virtual photons which appear in charged-particle collisions into real photons. These two types are Compton and nonlinear bremsstrahlung. The matrix elements are derived in the quasiclassical limit; account is taken of both new bremsstrahlung processes and the modification of the ordinary bremsstrahlung processes due to the screening of the fields of the virtual photons by the plasma. The calculations are valid for particles of arbitrary velocity; in particular, they are valid for ultrarelativistic and nonrelativistic particles. Rules are given for calculating the bremsstrahlung matrix elements in a plasma from the corresponding diagrams.