119138207
Lepton flavor violating photoleptonic effect
We study lepton flavor violating analogs of the photoelectric effect, with a final μ or T instead of an electron: γe → μ and γe → T. On the basis of the general parametrization of the matrix element of the electromagnetic current we estimate the upper limits for the cross sections and event rates of these processes, imposed by the current experimental bounds on μ → ey and T → eγ decays.
117509698
QCD NUCLEON MODEL WITH RELATIVISTIC OSCILLATOR INTERACTION BETWEEN CONSTITUENT QUARK
117569877
Lepton-nucleon scattering in the relativistic oscillator model
The scattering of charged leptons by a system of three quarks locked in by a relativistic oscillator potential is considered. The calculations are performed in the rest frame of the target, which allows the derivation of the explicit x and Q/sup 2/ dependences of the nucleon structure functions F/sub 1/(x,Q/sup 2/) and F/sub 2/(x,Q/sup 2/) and the quantity R = sigma/sub L//sigma/sub T/ in the region of moderate Q/sup 2/ values.
126120440
Spectra Particles From $\Lambda_c^+$ and $\Sigma_c^{++}$ Charmed Baryon Decays Produced in Neutrino $N$ Interactions
118014393
QCD analysis of deep inelastic lepton-scattering data
We have carried out a QCD analysis of data on deep inelastic lepton-scattering (using data of the collaborations BCDMS, EMC, and CDHS) in the leading and next-to-leading orders in the coupling constant ..cap alpha../sub s/. We have considered the effect of the sea quarks and gluons. We discuss the dependence of our results for ..lambda.. on effects of twist corrections, nuclear target effects, and heavy-quark production thresholds.
615085
Nucleon structure as a background for determination of fundamental parameters.
We consider deep inelastic (quasi)elastic lepton-nucleon scattering and investigate the possibilities of eliminating or suppressing theoretical uncertainties induced by the nucleon structure in measuring the standard model parameters or in searching for new physics. On the basis of rather general assumptions about nucleon structure we have obtained new relations between cross sections and neutral current parameters which are weakly dependent on the nucleon structure. We also investigate the dependence of the QCD $\ensuremath{\Lambda}$ parameter extracted from the data on the unknown large-scale nucleon structure and propose a modification of the conventional QCD predictions in which the dependence on this uncertainty factor is suppressed.
123021094
Analysis of intermediate-energy heavy-ion collisions within relativistic mean-field two-fluid model
A three-dimensional realization of the relativistic mean-field two-fluid model is described. First results of analyzing the inclusive data on the yield of nuclear fragments and pions, as well as the Plastic-Ball rapidity distributions of nuclear fragments are presented. For comparison, calculations within the conventional relativistic hydrodynamical model with the same mean fields are also performed. In spite of a pronounced sensitivity of the nuclear dynamics to the nuclear equation of state (more precisely, to the form of the mean fields), it is found that all the analyzed observables, except the pion spectra, appear to be fairly insensitive to it. The sensitivity to the nuclear stopping power is slightly higher. The original sensitivity of the rapidity distributions to the stopping power is smeared out by the Plastic-Ball filter and selection criterion. Nevertheless, one can conclude that the stopping power induced by the Cugnon parametrization of the nucleon-nucleon cross sections is not quite sufficient for a more adequate reproduction of the experimental data.
122934808
Relativistic mean field kinetic approach to hadron plasma and three-fluid dynamics
Abstract Proceeding from the Walecka mean field theory, a system of relativistic kinetic equations has been derived for the description of hadron plasma formation and evolution in nucleus-nucleus collisions at high energies. These equations comprise the dynamics of relativistic self-consistent σ and ω fields and, in particular, satisfactorily described ground states of nuclei. The constructed collision integrals are expressed via inclusive hadron-hadron cross sections and allow one to describe inelastic production of new particles in the process of the nucleus-nucleus collision. A method of solving these kinetic equations, based on a model representation of distribution functions, is proposed. An ansatz for the distribution functions is constructed proceeding from the assumption of incomplete stopping of nuclei in the collision process. This ansatz make it possible to reduce the set of kinetic equations to a set of equations of the three-fluid dynamics type for the parameters of the distribution functions.
16049954
Soft modes, resonances, and quantum transport
Effects of the propagation of particles that have a finite lifetime and an according width in their mass spectrum are discussed in the context of transport description. First, the importance of coherence effects (Landau-Pomeranchuk-Migdal effect) on the production and absorption of field quanta in nonequilibrium dense matter is considered. It is shown that classical diffusion and Langevin results correspond to a resummation of certain field-theory diagrams formulated in terms of full nonequilibrium Green's functions. General properties of broad resonances in dense and hot systems are discussed in the framework of a self-consistent and conserving Φ-derivable method of Baym by considering the examples of the ρ meson in hadronic matter and the pion in dilute nuclear matter. Further, we address the problem of a transport description that properly takes into account the damping width of the particles. The Φ-derivable method generalized to the real-time contour provides a selfconsistent and conserving kinetic scheme. We derive a generalized expression for the nonequilibrium kinetic entropy flow, which includes corrections from fluctuations and mass-width effects. In special cases, an H theorem is proven. Memory effects in collision terms contribute to the kinetic entropy flow that, in the Fermi liquid case, reproduces the famous bosonic-type T3lnT correction to the specific heat of liquid 3He. For the example of the pion-condensate phase transition in dense nuclear matter, we demonstrate the important role of the width effects within the quantum transport.
118620025
Quantum simulations of thermodynamic properties of strongly coupled quark-gluon plasma
A strongly coupled quark-gluon plasma (QGP) of heavy constituent quasi-particles is studied by a path-integral Monte-Carlo method. This approach is a quantum generalization of the model developed by Gelman, Shuryak and Zahed. It is shown that this method is able to reproduce the QCD lattice equation of state and also yields valuable insight into the internal structure of the QGP. The results indicate that the QGP reveals liquid-like rather than gas-like properties. At temperatures just above the critical one it was found that bound quark-antiquark states still survive. These states are bound by effective string-like forces and turns out to be colorless. At the temperature as large as twice the critical one no bound states are observed. Quantum effects turned out to be of prime importance in these simulations.
122100360
Kaon production in intermediate-energy nuclear collisions
Abstract Production of positive kaons in nuclear collisions at intermediate energies (∼1–2 GeV/nucleon) is studied within the 3-dimensional fluid dynamics combined with the hadrochemical kinetics for strangeness production. Sensitivity of the kaon probe to a form of the nuclear equation of state is analyzed. The model reproduces total and differential cross sections of Ne + NaF → K + + X and Ne + Pb → K + + X reactions at E lab = 2.1 GeV/nucleon, provided a soft equation of state is used. The pion-production data are also well described employing the same equation of state. Predictions are made for the current experiment on kaon production at the SIS accelerator. The obtained results are compared with the predictions of other models.