Showing papers on "Elementary particle published in 1981"
TL;DR: In this paper, the restrictions on elementary particle properties which can be derived from cosmological and astrophysical data are considered, and the inverse relations between micro- and macrophysics are also discussed, in particular the origin of the baryon asymmetry of the universe.
Abstract: The restrictions on elementary particle properties which can be derived from cosmological and astrophysical data are considered. The inverse relations between micro- and macrophysics are also discussed, in particular the origin of the baryon asymmetry of the universe.
318 citations
TL;DR: The string model of Artru and Mennessier predicts the fragmentation functions for mesons containing heavy quarks are concentrated near fractional momentumz∼1, with width ∼1/μ where μ is the mass of the heavy quark as mentioned in this paper.
Abstract: The string model of Artru and Mennessier predicts that the fragmentation functions for mesons containing heavy quarks are concentrated near fractional momentumz∼1, with width ∼1/μ where μ is the mass of the heavy quark.
209 citations
TL;DR: In this paper, proper treatment of the nonlocality of the nuclear optical potential resolved much of the apparent discrepancy between previous theoretical calculations and empirical values of the nucleon mean free path.
Abstract: It is shown that proper treatment of the nonlocality of the nuclear optical potential resolves much of the apparent discrepancy between previous theoretical calculations and empirical values of the nucleon mean free path.
160 citations
TL;DR: In this paper, it is pointed out that in general class of gauge models, there exist new contributions to neutrinoless double transition transitions that do not involve a Majorana neutrino but the decay of a doubly charged Higgs boson to electrons.
Abstract: It is pointed out that in a general class of gauge models, there exist new contributions to neutrinoless double $\ensuremath{\beta}$ transitions, that do not involve a Majorana neutrino but the decay of a doubly charged Higgs boson to electrons Explicit calculations for the case $^{48}\mathrm{Ca}$\ensuremath{\rightarrow}$^{48}\mathrm{Ti}$ indicate that for reasonable choice of parameters, this new contribution may dominate over that involving light or heavy Majorana neutrinos
113 citations
TL;DR: In this paper, the effect of neutral Higgs particles on low-energy weak interaction processes, like muon decay, tau decay, nuclear beta decay, pion decay, and some higher-order processes is analyzed.
90 citations
TL;DR: A brief review of the progress which has been made in understanding CP violation since its discovery is given in this paper, where experiments in Kaon systems and the measurement of parameters associated with long-lived neutral kaon decay are described.
Abstract: The author presents a brief review of the progress which has been made in understanding CP violation since its discovery. Experiments in Kaon systems and the measurement of parameters associated with long-lived neutral kaon decay are described. Theoretical ideas about CP violation are briefly considered. Forty eight references are given.
89 citations
TL;DR: In this article, a phase transition between ordinary hadronic matter and quark matter is detected in heavy-ion collisions by observing lepton-pair production spectra, based on a ''fireball model'' of nuclear collisions.
Abstract: We suggest that a phase transition between ordinary hadronic matter and quark matter is detectable in heavy-ion collisions by observing lepton-pair production spectra. Pair production rates are estimated on the basis of a ''fireball model'' of nuclear collisions. The presence of quark matter in the initial fireball should be revealed by an enhancement of the lepton-pair production rate at invariant masses between 200 and 600 MeV. Observation of lepton pairs within this mass interval is expected to serve as a sensitive diagnostic tool for probing the properties of bulk hadronic matter at high temperatures and compressions.
83 citations
TL;DR: In this paper, an analysis of the temporal development of particle intensity, composition, and anisotropies during diffuse particle events was conducted with an ultra-low energy charge analyzer (ULECA) sensor.
Abstract: An analysis is conducted of the temporal development of particle intensity, composition, and anisotropies during diffuse particle events. The observations were made with an ultra-low energy charge analyzer (ULECA) sensor. ULECA basically consists of an electrostatic deflection system and an array of solid state detectors. The simultaneous measurement of energy per charge and total energy makes it possible to determine the charge state of a particle. Spectra are derived by an iterative technique involving the numerical integration of particle spectra with the energy response functions of the individual detectors. The presented data are explained in terms of temporal and spatial structures in the upstream region. The temporal structures during the event onset are consistent with a time-dependent first-order Fermi acceleration model, as discussed by Scholer et al. (1980).
79 citations
TL;DR: In this article, the Weinberg-Salam model with two Higgs doublets upper bounds are derived for the Higgs boson masses by applying partial wave unitarity to the tree graphs of Higgs-Higgs scatterings.
Abstract: In the Weinberg-Salam model with two Higgs doublets upper bounds are derived for the Higgs boson masses by applying partial wave unitarity to the tree graphs of Higgs-Higgs scatterings. The upper bounds we find are
$$m_{H^ \pm } ,m_{H^0 }< 1.7TeVm_{\phi ^0 }< 1.4TeV,m_{h^0 }< 1.4 - 2.2TeV$$
.
78 citations
TL;DR: The O(..cap alpha/sub s/) perturbative quantum-chromodynamic corrections to weak, charged-current production of heavy quarks are evaluated in this article, and the residual corrections to the flavor-production structure functions are shown to be modest except for x'..-->..1 or Q/sup 2/..cc-bar splitting ''singularities'' into evolution of an intrinsic charm-sea component of the nucleon.
Abstract: The O(..cap alpha../sub s/) perturbative quantum-chromodynamic corrections to weak, charged-current production of heavy quarks are evaluated. For perturbative subtractions and parton densities defined via the electroproduction structure function F*/sub 2/, the residual corrections to ..nu..N flavor-production structure functions are shown to be modest except for x'..-->..1 or Q/sup 2/ ..cc-bar splitting ''singularities'' into evolution of an intrinsic charm-sea component of the nucleon. The longitudinal structure function due to charm production is computed and found to be substantial.
74 citations
TL;DR: In this paper, the multiplicity distributions of charged hadrons produced in νp interactions are studied using a sample of 7850 charged current interactions in BEBC, and a comparison is made with other lepton and hadron-induced reactions.
01 Jul 1981
TL;DR: In this article, it was shown that the true mass parameter which determines the transverse polarization of the hadrons is the mass of the one-loop diagram for quark-quark scattering.
Abstract: From an analysis of the polarization density matrix in QCD we have established that the true mass parameter which determines the transverse polarization of the hadrons is the mass of the hadron and not the mass of the quark. However, a rough estimate of the asymmetry of the pion which is based on the calculation of the one-loop diagram for quark-quark scattering, gives at p/sub T/roughly-equal1 GeV/c in the central region y = 0 a value of 3%.
TL;DR: In the early 1960s, with the advent of a new generation of particle accelerators, the list of elementary particles such as protons and neutrons collectively known as "hadrons" was growing rapidly as discussed by the authors.
Abstract: THE EXPERIMENTAL STATUS of quarks, hypothetical particles smaller than the electron, has excited debate within the physics community from 1977 on. The experimental developments that led up to this debate and the course the debate took up to mid-1979 reveal certain features of the experimental method that have received less attention from historians and philosophers than they deserve. In particular the quark debate reveals an intimate relationship between experimental practice and theoretical belief that has often been overlooked but has significant implications for our understanding of science. First, a thumbnail sketch of the history of quarks. In the early 1960s, with the advent of a new generation of particle accelerators, the list of elementary particles-strictly speaking the strongly interacting particles such as protons and neutrons, collectively known as "hadrons"-was growing rapidly. More than two hundred distinct hadrons have now been identified. In 1961 Murray Gell-Mann and Yuval Ne'eman introduced a symmetry scheme, known as "the eightfold way" or "SU(3)," which injected order into the proliferation of new hadrons by grouping them into multiplets, the members of each multiplet having closely related properties. I The success of this scheme has been unchallenged ever since. In 1964 Gell-Mann and George Zweig independently pointed out that this multiplet structure could be understood if one postulated the existence of a new layer of matter.2 They suggested that hadrons were not truly elementary particles, but were instead composites of just three subhadronic entities, which Gell-Mann christened "quarks." Combinations of quarks were supposed to make up hadrons, just as combinations of hadrons make up nuclei, combinations of nuclei and electrons make up atoms, and so on. The economy of Gell-Mann and Zweig's proposal was striking, explaining an apparently indefinitely rising number of hadrons in terms of only three constituent quarks. One question that immediately arose was, and is, could isolated quarks be found? Experimentalists began to search for them in a variety of ways, all predicated upon the unusual electric charges which had been postulated for quarks: either one third or two thirds of the electric charge of the electron (e). Since physicists had hitherto believed that all matter carried electric charge in
TL;DR: In this article, the authors measured the differential cross-sections for the vector and tensor mesons using various parametrizations for they and the dependence of their differential cross sections.
Abstract: Inclusive production of ϱ0,f, andg
0 mesons and ofK
0
,K
*0 (892), ϕ andK
*0(1430)mesons has been measured at ∼2.6 and
∼1.1 GeV/c in proton-proton interactions at $$\sqrt s = 52.5$$ GeV. The negative particle from the two-body decays of these resonances were identified by a threshold Cerenkov counter and used for triggering. Starting from the measured differential cross section, total inclusive cross sections for the vector and tensor mesons were determined using various parametrizations for they andp T dependence of the differential cross section. The experimental results are discussed in the framework of production models based on the parton picture. The strangeness suppresion factor λ=(0.30±0.10) due toSU(3) symmetry breaking of the quark sea is derived.
TL;DR: In this article, the photoproduction of 0-150-MeV charged pions from light nuclei is studied from a distorted wave impulse approximation (DWIA) approach, where the final nuclear states are restricted to a finite set of isospin analogs of excited states of the target nucleus.
TL;DR: In this article, the parton-recombination model plus SU(6) symmetry is used to relate polarizations in inclusive baryon production to those of the underlying constituent subprocesses.
Abstract: The parton-recombination model plus SU(6) symmetry is used to relate polarizations in inclusive baryon production to those of the underlying constituent subprocesses. A large number of predictions are given, none of which disagrees with experiment. It is suggested that the polarization arises via Thomas precession of the quarks' spins in the recombination process. This description accounts for all of the qualitative features of the baryon and antibaryon polarization data.
TL;DR: In this article, the production of scalar particles in a homogeneous isotropic spatially flat universe containing classical baryons and radiation is studied for regulated massless free-field theories without trace anomalies.
Abstract: The production of scalar particles in a homogeneous isotropic spatially flat universe containing classical baryons and radiation is studied for regulated massless free-field theories without trace anomalies. The pair-production probability is evaluated to lowest nonvanishing order in the parameter j = lp/sub b//p/sub r//sup ts3/4/, where l is the Planck length, p/sub b/ is the baryon energy density, and p/sub r/ is the radiation energy density, all in units where h = c = 1. For our universe japprox.10/sup -27/. The back reaction regulates the production of scalar particles near the singularity so that the probability to produce a pair in the volume occupied by one baryon over the history of the universe is finite, of order of magnitude jm/sub b/l, where m/sub b/ is the mass of a typical baryon, and therefore very small.
TL;DR: The present state of the theory of the interactions of high-energy hadrons, photons, and leptons with nuclei is reviewed in this paper, with emphasis placed on evidence for the quark-parton structure of hadrons in inelastic collisions with nucles and on effects resulting from an increase in the secondary-particle formation lengths.
Abstract: The present state of the theory of the interactions of high-energy hadrons, photons, and leptons with nuclei is reviewed. Emphasis is placed on evidence for the quark-parton structure of hadrons in inelastic collisions with nuclei and on effects resulting from an increase in the secondary-particle formation lengths. The discussion is based on the space-time picture of strong interactions which follows from the multiperipheral nature of high-energy inelastic reactions.
TL;DR: In this paper, the self-energy of nucleons inside symmetric nuclear matter is calculated by directing the attention to the energy and momentum dependent pieces which determine the quasiparticle properties.
TL;DR: The question of whether the ten generators for the Poincar\'e group as given in a field theoretical model can be reduced to the pure particle space without invalidating the commutation relations is studied in this article.
Abstract: The question of whether the ten generators for the Poincar\'e group as given in a field theoretical model can be reduced to the pure particle space without invalidating the commutation relations is studied We come to a positive answer in the framework of perturbation theory In a simple model of scalar particles exchanging scalar bosons we construct the generators in lowest order in the coupling constant and compare the expressions with the ones found by Foldy and Krajcik in a $\frac{1}{{c}^{2}}$ expansion We recover their result, but find in addition new terms in the interaction, which remained principally undetermined in their treatment Possible useful features of the "relativistically generalized Schr\"odinger equation" are pointed outNUCLEAR STRUCTURE Relativistic corrections
TL;DR: In this article, the neutral amplitudes for neutrino-quark scattering are calculated in the one-loop approximation of the standard Weinberg-Salam model of weak and electromagnetic interactions.
Abstract: The neutral amplitudes for neutrino-quark scattering are calculated in the one-loop approximation of the standard Weinberg-Salam model of weak and electromagnetic interactions. A careful analysis of renormalization procedure in the 't Hooft-Feynman gauge is presented. Apart from the photonic corrections which are subject to the ordinary QED analysis, purely weak corrections are of the order of one per cent in the amplitudes expressed in terms of the Fermi coupling constant.
TL;DR: In this paper, the one-loop contributions to the amplitude A and B in the standard electroweak gauge model were computed. But they were not considered in this paper, and the result is of importance if all mass effects are to be correctly taken into account.
Abstract: We compute exactly all the one-loop contributions to the amplitude A..-->..B..gamma.., where A and B are fermions of the same charge, but different flavor, in the standard electroweak gauge model. The result is of importance if all mass effects are to be correctly taken into account.
TL;DR: The excitation functions of twenty nuclear reactions induced by protons of up to 85 MeV incident upon 48Ti and 50Ti targets have been measured as mentioned in this paper, most of these involve the emission of one to three alpha particles.
Abstract: The excitation functions of twenty nuclear reactions induced by protons of up to 85 MeV incident upon48Ti and50Ti targets have been measured. Most of these involve the emission of one to three alpha particles.
TL;DR: The author presents a brief review of the progress which has been made in understanding CP violation since its discovery and experiments in Kaon systems and the measurement of parameters associated with long-lived neutral kaon decay.
Abstract: The author presents a brief review of the progress which has been made in understanding CP violation since its discovery. Experiments in Kaon systems and the measurement of parameters associated with long-lived neutral kaon decay are described. Theoretical ideas about CP violation are briefly considered. Forty eight references are given.
TL;DR: In this paper, the necessity of a separation of quarks and gluons in qq-barg three-jet events in e/sup +/e/sup -/ annihilation in order to obtain quantitative tests of quantum chromodynamics is discussed.
Abstract: We discuss the necessity of a separation of quarks and gluons in qq-barg three-jet events in e/sup +/e/sup -/ annihilation in order to obtain quantitative tests of quantum chromodynamics. The possibility of such a separation is investigated with special emphasis on the case that one or two of the jets are identified as quark jets by a semileptonic decay of a c or b quark. It is shown in detail how gluon energy spectra and gluon-jet properties can be deduced from these measurements.
TL;DR: In this paper, the authors examined the possibility that the orthogonal state f/sup perpendicular/ = -sinthetaVertical Barqq-bar>+costheta Vertical Bargg> decouples from π pi pi.., and found sin/sup 2/theta = 0.15/sup + 0.05/sub -0.06/.
Abstract: SU(3) and SU(6) suggest GAMMA(f..--> pi pi..) = 112--115 MeV for a quark-antiquark state, while the observed value is 148 +- 17 MeV. This small discrepancy permits a non-qq-bar admixture (''gg'') in the f: Vertical Barf> = costhetaVertical Barqq-bar>+sinthetaVertical Bargg>. We examine the possibility that the orthogonal state f/sup perpendicular/ = -sinthetaVertical Barqq-bar>+costhetaVertical Bargg> decouples from ..pi pi.., and find sin/sup 2/theta = 0.15/sup +0.05//sub -0.06/. Consequences include a diminished predicted rate for f..--> gamma gamma.., in qualitative accord with experiment; a mass formula f/sup perpendicular/-A/sub 2/ = cot/sup 2/theta(A/sub 2/-f) yielding f/sup perpendicular/ in the range 1.45--1.87 GeV/c/sup 2/; and predictions for f/sup() perpendicular/ spectra as produced in ..gamma gamma -->..f/sup() perpendicular/ or J/psi..-->..f/sup() perpendicular/+..gamma.. and detected in f..-->..KK-bar, rho..gamma.., or ..gamma gamma... The width of f/sup perpendicular/ is estimated to be no more than 40 MeV under these assumptions.
TL;DR: In this article, it was shown that in Weinberg-salam theory, there are metastable states in which the Higgs field is expelled from the interior of a torus by a trapped quantum of the $Z$ field.
Abstract: It is shown that, in the Weinberg-Salam theory, there are metastable states in which the Higgs field is expelled from the interior of a torus by a trapped quantum of the $Z$ field. Called "vorticons," they are scalar particles that decay via the decay modes of the $Z$. A variational calculation estimates the mass to be of the order of 3000 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$. The "macroscopic" vortex rings, in which the trapped $Z$ field is so strong that it becomes classical, are not even metastable; they tend to collapse into vorticons.
01 Feb 1981
TL;DR: In this article, it was shown that the proton has a non-negligible uudcc-bar Fock component at high x/sub F/ in hadron collisions.
Abstract: Recent data give unexpectedly large cross-sections for charmed particle production at high x/sub F/ in hadron collisions. This may imply that the proton has a non-negligible uudcc-bar Fock component.
01 Dec 1981
TL;DR: In this paper, the authors presented the observables for the A = 3 bound state with a two-pion exchange three-body force added to the de Tourreil and Sprung realistic nucleon-nucleon interaction.
Abstract: We present the observables for theA=3 bound state with a two-pion exchange three-body force added to the de Tourreil and Sprung realistic nucleon-nucleon interaction. This results mainly in increasing the binding energy by 650 keV. In the framework of the impulse approximation, we find no sensible improvement for the electromagnetic form factors, and no central depression for the He3 charge density with point nucleons. We compute the contribution of the three-body force to then-d doublet scattering length whose agreement with experiment is improved.