896237
Electroproduction of charmonia off nuclei
In a recent publication we have calculated elastic charmonium production in ep collisions employing realistic charmonia wave functions and dipole cross sections and have found good agreement with the data in a wide range of s and Q^2. Using the ingredients from those calculations we calculate exclusive electroproduction of charmonia off nuclei. Here new effects become important, (i) color filtering of the c-cbar pair on its trajectory through nuclear matter, (ii) dependence on the finite lifetime of the c-cbar fluctuation (coherence length) and (iii) gluon shadowing in a nucleus compared to the one in a nucleon. Total coherent and incoherent cross sections for C, Cu and Pb as functions of s and Q^2 are presented together with some differential cross sections. The results can be tested with future electron-nucleus colliders or in peripheral collisions of ultrarelativistic heavy ions.
117509698
QCD NUCLEON MODEL WITH RELATIVISTIC OSCILLATOR INTERACTION BETWEEN CONSTITUENT QUARK
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.
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.
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.
120068071
Partial-transparency effects in heavy-ion collisions at energies of the order of 1 GeV/nucleon
Abstract A model of heavy-ion collisions at energies E lab ∼ 1 GeV/nucleon taking into account the effects of incomplete statistical equilibrium in highly-excited nuclear matter is presented. The collision process is considered as the interaction of two flows of nucleons decelerating each other. This process is described within the framework of a relativistic kinetic approach employing the Fokker-Planck approximation. Assuming two-flow nonequilibrium the momentum distribution function is represented as a sum of two maxwellian distributions displaced by the average relative velocity of flows. Equations for time evolution of space-averaged velocities and internal energies of flows are derived. These equations contain a single model parameter, i.e. the effective deceleration length λ d . Using the firestreak model geometry inclusive cross sections of protons and composite particles (d, t) in the reactions Ne + NaF, Ar + KCl and Ar + Pb are calculated at various values of E lab . In contrast to the firestreak model, a complete stopping of colliding tubes in the centre-of-mass frame was not assumed in the present calculation. Composite particle spectra are calculated on the basis of the coalescence model. The theory is thoroughly compared with the experimental data. The approach suggested allows us to reproduce a two-humped structure in the rapidity distributions of the secondary particles. The experimental data analysis leads to the value λ d = 8 fm for E lab = 0.8 GeV/nucleon, which is in good agreement with the estimation based on experimental NN cross sections.
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.
14163235
SOFT MODES, QUANTUM TRANSPORT AND KINETIC ENTROPY
The effects of the propagation of particles which have a finite life-time and an according width in their mass spectrum are discussed in the context of transport descriptions. In the first part the coupling of soft photon modes to a source of charged particles is studied in a classical model which can be solved completely in analytical terms. The solution corresponds to a re-summation of certain field theory diagrams. The general properties of broad resonances in dense finite temperature systems are discussed at the example of the $\rho$-meson in hadronic matter. The second part addresses the problem of transport descriptions which also account for the damping width of the particles. The Kadanoff--Baym equation after gradient approximation together with the $\Phi$-derivable method of Baym provides a self-consistent and conserving scheme. Memory effects appearing in collision term diagrams of higher order are discussed. 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 proved. Memory effects in collision terms provide contributions to the kinetic entropy flow that in the Fermi-liquid case recover the famous bosonic type $T^3 \ln T$ correction to the specific heat of liquid Helium-3.
125840079
Quantum Color Dynamic Simulations of the Strongly Coupled Quark-Gluon Plasma
A strongly coupled plasma of quark and gluon quasiparticles is studied by combination of Path integral Monte Carlo and quantum Wigner dynamics simulations. This method extends previous classical nonrelativistic simu-lations based on a color Coulomb interaction to the quantum regime. First results for the momentum-momentum autocorrelation function and diffusion constant are presented (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)