Showing papers on "Elementary particle published in 1979"
TL;DR: In this article, it is shown that at a sufficiently large temperature a phase transition takes place after which almost all elementary particles in the hot super-dense matter become massless and weak interactions become long-range like electromagnetic interactions.
Abstract: Reviews phase transitions in super-dense matter, which consists of particles interacting in accordance with the unified gauge theories of weak, strong and electromagnetic interactions It is shown that at a sufficiently large temperature a phase transition takes place after which almost all elementary particles in the hot super-dense matter become massless and weak interactions become long-range like electromagnetic interactions Analogous phenomena may take place with an increase of fermion density in cold dense matter, and also in the presence of external fields and currents Phase transitions in gauge theories lead to a time dependence of the masses of particles, of coupling constants and of the cosmological term in the expanding Universe, to the appearance of a domain structure of vacuum, to substance energy non-conservation, to a possibility of obtaining the 'hot' Universe starting with a 'cold' one, and to some other unusual effects important for cosmology and for elementary particle physics
605 citations
TL;DR: Hadron jets produced in e+e− annihilation between 13 GeV and 31.6 GeV in c.m. energy at PETRA are analyzed in this article, showing that the broadening of the jets is not uniform in azimuthal angle around the quark direction but tends to yield planar events with large and growing transverse momenta in the plane and smaller transverse momentsa normal to the plane.
317 citations
TL;DR: In this article, the asymptotic behavior of the form factor in quantum electrodynamics is calculated in case the photon has a mass, and the result is essentially that found by Sudakov.
Abstract: The asymptotic behavior of the form factor in quantum electrodynamics is calculated in case the photon has a mass. The technique used takes into account all logarithms in ${q}^{2}$ but neglects inverse powers of ${q}^{2}$. The result is essentially that found by Sudakov. In order to obtain this result the large-$n$ behavior of ${\ensuremath{\gamma}}_{n}$ is obtained.
245 citations
TL;DR: In this article, the authors discuss three different mechanisms for the capture of a light particle from a bare heavy nucleus by another bare heavy nuclei which is incident with a very high relative velocity, and a comparison of the relative importance of the different mechanisms in the case of electron capture from hydrogenlike ''atoms''.
Abstract: Within the nonrelativistic approximation the authors discuss three different mechanisms for the capture of a light particle from a bare heavy nucleus by another bare heavy nucleus which is incident with a very high relative velocity. The emphasis is on physical interpretation. For each mechanism a ''physical'' (i.e., more readily comprehensible) derivation is given of the asymptotic form of the total cross section, and a comparison is made of the relative importance of the different mechanisms in the case of electron capture from hydrogenlike ''atoms.'' The first mechanism is knock-on capture, where the two nuclei have equal masses and simply switch places. The second mechanism is radiative capture, which occurs with the emission of a photon. The third mechanism, which is perhaps the most interesting one, is double scattering, first suggested within the framework of classical mechanics by Thomas in 1927.
224 citations
TL;DR: In this paper, the theory and phenomenology of such a situation were examined as a guide for future experimental searches in theories with more scalar multiplets than the minimal Weinberg-Salam model, where there will exist charged physical Higgs particles in addition to the neutral Higgs particle.
Abstract: In theories with more scalar multiplets than the minimal Weinberg-Salam model, there will exist charged physical Higgs particles, in addition to the neutral Higgs particle. We examine the theory and phenomenology of such a situation as a guide for future experimental searches.
222 citations
TL;DR: In this article, the production of hadrons, leptons, and quarks in the early universe is described in terms of departure from thermal equilibrium, and the AIP model is used.
Abstract: Production of hadrons, leptons, and quarks in the early universe is described in terms of departure from thermal equilibrium. (AIP)
159 citations
TL;DR: In this article, the neutrino energy range 30-200 GeV was investigated and the results were in agreement with the expectations of the quark parton model and QCD.
Abstract: We present results on charged current inclusive neutrino and antineutrino scattering in the neutrino energy range 30–200 GeV. The results include a) total cross-sections; b)y distributions; c) structure functions; and d) scaling violations observed in the structure functions. The results, as well as their comparison with the results of electron and muon inclusive scattering, are in agreement with the expectations of the quark parton model and QCD.
126 citations
TL;DR: In this article, it was shown that the Higgs is unlikely to be detected at LEP if its mass is greater than 150 GeV, which is the threshold for the existence of a heavy Weinberg-salam-type neutral Higgs boson.
126 citations
TL;DR: In this paper, the level structures of146Gd and147Gd have been investigated by in-beamγ-ray ande− spectroscopy with (α, xn) reactions on enriched Sm targets.
Abstract: The level structures of146Gd and147Gd have been investigated by in-beamγ-ray ande− spectroscopy with (α, xn) reactions on enriched Sm targets. Detailed level schemes up to ∼4 MeV, which differ radically from earlier schemes, are reported. The energy levels are characterized as particle-hole excitations using empirical single particle energies and two nucleon interactions. Analysis of pure 1p 1h proton excitations demonstrates that theZ=64 andN=82 energy gaps are about equally large.
125 citations
TL;DR: In this article, the π+ production is dominated by longitudinally polarized photons and can be described by one pion exchange at small |t| and at low |t | the transverse (π+¯¯¯¯n) cross section drops steeply withQ petertodd2, but remains roughly constant forQ�2≧0.5 GeV2.
Abstract: The reactionsΣ
v
p→π+
n,K
+
Λ,K
+
∑
0 andΣ
v
n→π+
n were studied at invariant hadronic masses around 2.2. GeV forQ
2=0.06, 0.28, 0.70, and 1.35 GeV2. The main results are: At small |t| the π+ production is dominated by longitudinally polarized photons and can be described by one pion exchange. At low |t| the transverse (π+
n) cross section drops steeply withQ
2, but remains roughly constant forQ
2≧0.5 GeV2. For |t⊢≧0.8 GeV2, (π+
n/dt) is almost independent ofQ
2. The integrated cross section (π+
n) shows a similarQ
2-dependence asσ
tot (γ
v
p) forQ
2≧0.28 GeV2. The ratioσ(π-
p)/σ(π+
n) atQ
2=0.70 and 1.35 GeV2 for |t|≧0.6 GeV2 is smaller than in photoproduction and close to 1/4. The ratioσ(K
+
∑
0 decreases steeply withQ
2 following roughly the predictions of the quark-parton model.
01 Jan 1979
TL;DR: The characteristic value of the electromagnetic field intensity in quantum electrodynamics is studied and presented in this paper, where general remarks are given on processes in an intense electromagnetic field and their description is detailed.
Abstract: The characteristic value of the electromagnetic field intensity in quantum electrodynamics is studied and presented. General remarks are given on processes in an intense electromagnetic field and their description is detailed. Photon emission by electron in the field of an intense electromagnetic wave and pair production by a photon in the field of an intense electromagnetic wave are discussed. The authors examine shift and splitting of the atomic level by electromagnetic wave fields. Radiative corrections are presented.
TL;DR: In this paper, the authors examined the high-temperature behavior of softly broken symmetries such as gauge invariance as well as parity and time-reversal invariance in a class of models of quantum flavor dynamics.
Abstract: We have examined the high-temperature behavior of softly broken symmetries such as gauge invariance as well as parity and time-reversal invariance in a class of models of quantum flavor dynamics. We find that there exist domains of coupling parameters of the theory, for which the above symmetries remain broken at high temperatures. Such models have the potential to explain matter-antimatter asymmetry in the universe while at the same time providing a cure for the strong CP problem. The fermion and boson masses in these models increase with temperature. A signature for such models is the existence of heavy Higgs bosons (with m/sub H/> or approx. =m/sub W/).
TL;DR: In this article, the photon structure function F/sub 2/sup lt. slash/ was generalized to the next-to-the-leading order of asymptotic freedom.
Abstract: We generalize Witten's calculation of the photon structure function F/sub 2//sup lt. slash/ to the next-to-the-leading order of asymptotic freedom. Except for the second moment of F/sub 2//sup lt. slash/, the result is independent of the unknown matrix elements of quark and gluon operators between the photon states. The nonleading corrections turn out to be large.
TL;DR: In this article, the authors formulate the problem of quark confinement in the infinite-momentum frame as a many-body problem, where quarks and gluons can be thought of as nonrelativistic particles moving in the two-dimensional transverse space with mechanical mass related to the longitudinal momentum.
Abstract: We formulate the problem of quark confinement in the infinite-momentum frame. In this frame the dynamics is naturally described as a many-body problem: Quarks and gluons can be thought of as nonrelativistic particles moving in the two-dimensional transverse space with mechanical mass related to the longitudinal momentum ${P}^{+}$. In this language, a natural quark-confining mechanism is the condensation of gluons along a tube joining a separated quark and antiquark. This condensation is favored by two circumstances: (1) The fact that bare gluons are massless reduces the minimum energy for gluon pair production to zero, and (2) the octet color structure allows gluons to form into chains with long-range attractive nearest-neighbor interactions. We investigate the viability of this mechanism first in the limit ${N}_{c}\ensuremath{\rightarrow}\ensuremath{\infty}$, ${N}_{c}{g}^{2}$ fixed, where ${N}_{c}$ is the number of colors in the theory. We analyze in detail a simplified version of the ${N}_{c}\ensuremath{\rightarrow}\ensuremath{\infty}$ dynamics which preserves the essential features of the full problem. This simplified model exhibits quark confinement and describes mesons as relativistic open strings. It also yields a relationship between the Regge slope $\ensuremath{\alpha}$' and the scale ${\ensuremath{\mu}}_{0}$, measured in deep-inelastic leptoproduction: ${\ensuremath{\mu}}_{0}^{2}\ensuremath{\approx}\frac{2}{(\ensuremath{\pi}\sqrt{3}{\ensuremath{\alpha}}^{\ensuremath{'}})}\ensuremath{\approx}0.4$ Ge${\mathrm{V}}^{2}$, which is not too far from the experimental number 0.25 Ge${\mathrm{V}}^{2}$. We discuss next the problem of finite ${N}_{c}$. We argue that the $\frac{1}{{N}_{c}}$ expansion is likely to have a vacuum instability which must be handled nonperturbatively before $\frac{1}{{N}_{c}}$ corrections can be calculated. We suggest that the true vacuum is a condensate of closed strings which have a finite density by virtue of repulsive interactions inherent in the fourgluon term in the Hamiltonian. A crude estimate of the condensate energy density yields an order-of-magnitude relation of the form $\ensuremath{\epsilon}\ensuremath{\sim}\frac{{{N}_{c}}^{2}}{{\ensuremath{\alpha}}^{2}}$. ${\ensuremath{\epsilon}}^{\ensuremath{-}\frac{1}{4}}$ should be a rough estimate of the thickness of the string.
TL;DR: In this paper, the Higgs-boson production cross sections were estimated by calculating the subprocess gluon +gluon and heavy-quark-antiquark pair.
Abstract: We estimate the Higgs-boson production cross sections dsigma/dy and dsigma/dydq/sup ts2//sub T/ at y = 0 in p (p-bar) p collisions by calculating the subprocess gluon + gluon ..-->.. Higgs boson + heavy-quark-antiquark pair.
TL;DR: In this paper, the Weinberg-Salam SU/sub 2/ x U/sub 1/ gauge model was shown to have a multiplicatively conserved quantum number, where π = +-1.
Abstract: The leptons ..nu../sub e/, e, ..nu../sub ..mu../, ..mu.., ..nu../sub tau/, tau, and analogously the quarks u, d, c, s, t, b, are unified within the Weinberg-Salam SU/sub 2/ x U/sub 1/ gauge model without enlarging the gauge group. The result is a theory in which the familiar leptons, quarks, and gauge bosons, plus some extra Higgs bosons necessary for unification, all carry a new multiplicatively conserved quantum number ..pi.. = +- 1. The most striking results of this unification are (1) ..pi.. conservation forbids ..mu.. ..-->.. e..gamma.. but allows the Higgs-boson-mediated decays tau ..-->.. l..gamma.. (l = e or ..mu..) and tau ..-->.. ..mu..ee or e..mu mu.., at a calculable rate with a calculable lower limit; (2) for quarks, two of the three Cabibbo angles must be zero, so that the b quark (assumed lighter than t) decays only via Higgs-boson exchange, always semileptonically and always with lepton-number violation, e.g., b ..-->.. de/sup +/..mu../sup -/. This singular prediction will confirm or exclude the model as soon as b-flavored mesons are discovered. These and other phenomenological consequences of this unification are explained, and rates are estimated.
TL;DR: In this paper, the authors examined the magnitude of the cosmological baryon asymmetry arising in several of the standard models of CP violation, including the Kobayashi-Maskawa model.
Abstract: We have examined the magnitude of the cosmological baryon asymmetry arising in several of the standard models of CP violation. Agreement with the experimental baryon to photon number ratio n/sub B//n/sub ..gamma../ approx. = 10/sup -8/ is obtained in models where superheavy Higgs mesons decay with complex amplitude into other Higgs mesons. By contrast, in the Kobayashi-Maskawa model n/sub B//n/sub ..gamma../ approx. = O (10/sup -20/).
01 Jun 1979
TL;DR: In this paper, the effect of two-body collisions on the Hartree-Fock (TDHF) theory is considered and a collision integral is added to the Boltzmann equation to obtain conserving approximations.
Abstract: The time-dependent Hartree-Fock (TDHF) theory is generalized in order to include the effect of two-body collisions (i.e. the residual interaction). This is achieved by adding a collision integral into the TDHF equations, similar to the one ordinarily used in the Boltzmann equation. It is shown, that two-body collisions arise from the imaginary part of the effective interaction between two nucleons whereas the Hartree-Fock field is associated to the real part of the same interaction. There is thus no double counting when the collisions are added to a single particle field. Various approximations for the collision integral are discussed and their accuracy evaluated. Special effort is made in order to obtain conserving approximations. It is shown that for discrete fields, energy as well as momentum conservation is achieved by off-shell scattering processes. In the light of a previous paper, it is argued that two-body collisions should dominate the irreversible processes above some critical energy (roughly 200 MeV per nucleon). Below this energy the irreversible effects due to the single particle field and the collisions are expected to be of the same order of magnitude.
TL;DR: In this article, it was shown that relativistic particles may be described in terms of conformal 0(2,4)-symmetric actions and that this is the maximal √ O(m,n) symmetry.
Abstract: It is shown that relativistic particles may be described in terms of conformal 0(2,4)-symmetric actions and that this is the maximal $\mathrm{O}(m,n)$ symmetry. The position is given as a six-component object where two are made fictitious by the introduction of two additional local invariances to the conventional reparametrization invariance. Spinning particles are obtained through the superspace technique, and interaction with an external electromagnetic field is obtained through minimal coupling in the case of massless particles.
Journal Article•
TL;DR: In this article, the Vavilov-Cerenkov radiation in the case of electromagnetic fields has been studied, where the emitted particles with a given energy are concentrated near some polar angle and possess high transverse momentums (at least several GeV/sec).
Abstract: During the interaction of extremely high energy (E/sub lab/> or approx. =10 TeV) hadrons a hadron radiation can appear, similar to the Vavilov-Cerenkov radiation in the case of electromagnetic fields. The process exhibits an energy-threshold character. The emitted particles with a given energy are concentrated near some polar angle and possess high transverse momentums (at least several GeV/sec).
TL;DR: The present pattern of six almost identical SU(2)L × U(1) quark or lepton doublet-singlet sets appears to indicate that all matter is made of one fundamental fermion set as mentioned in this paper.
TL;DR: In this article, the authors unify the n quark and n lepton generations within the standard SU/sub 2/x U/sub 1/gauge model by means of the generation symmetry group S/sub n.
Abstract: We unify the n quark and n lepton generations within the standard SU/sub 2/ x U/sub 1/ gauge model by means of the generation symmetry group S/sub n/. We show that no more than five generations of quarks and leptons can be incorporated into the theory. The resultant model always has either one or two exactly conserved multiplicative quantum numbers with eigenvalue +- 1 carried by each generation. These constrain the number of nonzero weak mixing angles between generations so that, even if there exist six or eight quarks, exact Cabibbo universality can hold naturally in the light-four-quark sector. The b quark must then always decay semileptonically with lepton-flavor violation, a key test.
Journal Article•
TL;DR: The total cross section of interaction of rho mesons at high energies was calculated in quantum chromodynamics in lowest-order perturbation theory as discussed by the authors, in agreement with predictions of the additive quark model.
Abstract: The total cross section of interaction of rho mesons at high energies is calculated in quantum chromodynamics in lowest-order perturbation theory. The result is in agreement with predictions of the additive quark model.
TL;DR: In this paper, the authors used the quark model framework to calculate the weak decays of the lowest lying charmed baryons into ground state baryon and mesons.
Abstract: We use the quark model framework to calculate the weak decays of the lowest lying charmed baryons into ground state baryons and mesons. We present detailed results on the predicted flavour and multipole composition of the final state configurations which can be tested in the near future. For the decays 1/2+→1/2++0− we also give symmetry and current algebra estimates which we compare with the quark model results. Semileptonic branching ratios in charmed baryon decays are calculated to be of the order of ∼5%. The total lifetime of charmed baryons is predicted to be ∼7 10−14 s which is 5–10 times smaller than the free quark model estimate.
01 Jun 1979
TL;DR: The level structures of the N=82 and N=83 nuclei147Tb and148Tb have been studied by means of (α, 8n) and (α 7n) reactions induced by 68 to 110 MeVα particle bombardments of151Eu targets as mentioned in this paper.
Abstract: The level structures of theN=82 andN=83 nuclei147Tb and148Tb have been studied by means of (α, 8n) and (α,7n) reactions induced by 68 to 110 MeVα particle bombardments of151Eu targets. In-beam conversion electron measurements have established that isomers withT1/2=4.8(6)ns in147Tb andT1/2=22(1)ns in148Tb decay byM2+E3 transitions to the ground states. The measuredB(E3) values show that the isomeric states arise from the coupling of the valence nucleon(s) to the146Gd core octupole. Particlephonon coupling in these nuclei and in the one-neutron nucleus147Gd is discussed and compared with well known cases involving the208Pb core. The higher lying yrast states in the two Tb nuclei are described as shell-model particle-hole excitations using empirical single particle energies and nucleon-nucleon interactions.
TL;DR: Theoretically, the hypothetical existence of new color interactions, which participate in the spontaneous breaking of the weak-interaction group, will in general lead to relatively light composite pseudo Goldstone bosons as mentioned in this paper.
Abstract: The hypothetical existence of new color interactions, which participate in the spontaneous breaking of the weak-interaction group, will in general lead to relatively light composite pseudo Goldstone bosons. Their production and decay characteristics are analyzed to be close to, yet actually distinguishable from, those of the elementary Higgs bosons of the Weinberg-Salam model.
TL;DR: In this paper, the quasilinear theory of collisionless test particle diffusion in stochastic magnetic fields is extended to include the effects of finite gyroradius, particle drifts, and magnetic trapping.
Abstract: The quasilinear theory of collisionless test particle diffusion in stochastic magnetic fields is extended to include the effects of finite gyroradius, particle drifts, and magnetic trapping. Runaway confinement is substantially improved relative to earlier estimates which assumed that particles exactly followed field lines. Trapped particles are not expected to be stochastic.
TL;DR: In this article, the effect of flavor mixing on SU(5) grand unified theories with arbitrary number of fermion families was discussed and it was shown that in the simplest model with only one {5} Higgs multiplet, all fermions interactions with Higgs as well as gauge bosons are describable in terms of a single mixing matrix.
Abstract: I discuss the effect of flavor mixing on proton-decay Hamiltonian in SU(5) grand unified theories with arbitrary number of fermion families and show that in the simplest model with only one {5} Higgs multiplet, all fermion interactions (with Higgs as well as gauge bosons) are describable in terms of a single mixing matrix. For the more complicated case of several {5} multiplets, the above feature persists for gauge-boson interactions though not for Higgs bosons.
TL;DR: In this article, the mixing angle between the light (u,d,s,c) and the heavy (t,b,g,h) quarks is computed and the masses of all the predicted fermions are predicted.
Abstract: We attempt to use a horizontal gauge symmetry in addition to SU(2)/sub L/ x U(1) to understand Cabibbo universality and the fermion masses. We compute the mixing angle between the light (u,d,s,c) and the heavy (t,b,g,h) quarks and show that it is small. The Cabibbo angle remains undetermined. In this scheme flavor-changing neutral currents exist between the heavy and the light fermions. Owing to this the picture of the decay of the b quark differs from the currently held view. The masses of all the predicted fermions are predicted.