126039083
Approximated Solution of {QCD} Evolution Equations
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.
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.
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.
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.
182432079
SPECTRALITY OF GELL-MANN-LOW FUNCTION
119251075
Alternative Scenarios of Relativistic Heavy-Ion Collisions: I. Baryon Stopping
Simulations of relativistic heavy-ion collisions within the three-fluid model employing a purely hadronic equation of state (EoS) and two versions of the EoS involving deconfinement transition are presented. The latter are an EoS with the first-order phase transition and that with a smooth crossover transition. The model setup is described in detail. The analysis is performed in a wide range of incident energies 2.7 GeV $< \sqrt{s_{NN}} <$ 39 GeV in terms of the center-of-mass energy. Results on proton and net-proton rapidity distributions are reported. Comparison with available data indicate certain preference of the crossover EoS. It is found that predictions within deconfinement-transition scenarios exhibit a "peak-dip-peak-dip" irregularity in the incident energy dependence of the form of the net-proton rapidity distributions in central collisions. This irregularity is a signal of deconfinement onset occurring in the hot and dense stage of the nuclear collision.
118464063
On freeze-out problem in relativistic hydrodynamics
A finite unbound system which is equilibrium in one reference frame is in general nonequilibrium in another frame. This is a consequence of the relative character of the time synchronization in the relativistic physics. This puzzle was a prime motivation of the Cooper-Frye approach to the freeze-out in relativistic hydrodynamics. Solution of the puzzle reveals that the Cooper-Frye recipe is far not a unique phenomenological method that meets requirements of energy-momentum conservation. Alternative freeze-out recipes are considered and discussed.
116146206
Multifluid dynamics of intermediate-energy heavy-ion collisions
An extension of the multifluid approach to the description of heavy-ion collisions is proposed. A three-fluid model involving mean {sigma} and {omega} fields is formulated for heavy-ion collisions at incident energies around 1 GeV per nucleon. It is a natural extension of a similar two-fluid model developed in our recent papers and is intended to obtain a closer approximation to the complete relativistic mean-field kinetic theory. The collisional coupling between the fluids is formulated in terms of hadron-hadron cross sections (which take into account Pauli blocking). The model contains no fitting parameters. The relativistic mean-field three-fluid model (RMF-3FM) is tested for the case of thermalization in counter-streaming nuclear fluids. Comparison with the results obtained in relativistic Landau-Vlasov kinetics and in a similar two-fluid model (RMF-2FM) shows that the RMF-3FM reproduces the gross properties of the equilibration better than the RW-2FM. 30 refs., 6 figs.
119538947
Towards a Quantum Transport Description of Particles with finite Mass Width 1
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 second part addresses the derivation of transport equations which also account for the damping width of the particles. The $\Phi$-derivable method of Baym is used to derive a self-consistent and conserving scheme. For this scheme a conserved energy-momentum tensor can be constructed. Furthermore, a kinetic entropy can be derived which besides the standard quasi-particle part also includes contributions from fluctuation.
116272686
Dynamical Instabilities in Relativistic Heavy-Ion Collisions and Associated Phenomena