118548456
Meson vacuum phenomenology in a three-flavor linear sigma model with (axial-)vector mesons
We study scalar, pseudoscalar, vector, and axial-vector mesons with non-strange and strange quantum numbers in the framework of a linear sigma model with global chiral $U(N_f)_L \times U(N_f)_R$ symmetry. We perform a global fit of meson masses, decay widths, as well as decay amplitudes. The quality of the fit is, for a hadronic model that does not consider isospin-breaking effects, surprisingly good. We also investigate the question whether the scalar $\bar{q}q$ states lie below or above 1 GeV and find the scalar states above 1 GeV to be preferred as $\bar{q}q$ states. Additionally, we also describe the axial-vector resonances as $\bar{q}q$ states.
56157029
Zero temperature properties of mesons in a vector meson extended linear sigma model
A three flavor linear sigma model with vector and axial-vector mesons is discussed. Preliminary results concerning on the symmetry breaking pattern, the question of parameterization, as well as the resulting meson masses are presented.
118091415
Chiral symmetry, di-electrons and charm
We survey some prospects of identifying further in-medium modifications of hadrons in a strongly interacting medium with respect to ongoing experiment series of the HADES Collaboration and planned experiments of the CBM Collaboration at FAIR. Di-electrons, strange and charm mesons are considered and their potential for signaling imprints of chiral restoration is highlighted.
118814310
Thermal, chemical and spectral equilibration in heavy-ion collisions
Abstract We have considered the equilibration in relativistic heavy ion collisions at energies 1–7 A GeV using our transport model. We applied periodic boundary conditions to close the system in a box. We found that the thermal equilibration takes place in the first 20–40 fm/ c whose time is comparable to the duration of a heavy ion collision. The chemical equilibration is a much slower process and the system does not equilibrate in a heavy ion collision. We have shown that in the testparticle simulation of the Boltzmann equation the mass spectra of broad resonances follow instantaneously their in-medium spectral functions as expected from the Markovian approximation to the Kadanoff–Baym equations employed via the (local) gradient expansion.
32667237
Heavy ion collisions and anisotropic hydrodynamics.
The study of the isotropization of momentum is important in heavy ion collisions. To do this we construct a generalized hydrodynamical equation system, in which the anisotropy of the momentum distribution is added as a new variable. These equations are derived from the moment equations of the relativistic Boltzmann equation where the closure of the set is achieved by assuming a particular class of initial conditions. The equations are then explicitly solved for two uniform interpenetrating hadron streams. The collision cross sections are the bare hadron cross sections; the presence of the other hadrons can be simulated by the use of a density- and energy-density-dependent temperature and mass, taken over from self-consistent calculations. The results are compared with other theoretical results. We find that the isotropization occurs sufficiently rapidly for medium energy head-on collisions to reach local thermal equilibrium.
119240638
Dilepton production in pion-nucleon collisions in an effective field theory approach
We present a model of electron-positron pair production in pion-nucleon collisions in the exclusive reaction \pi N -> Ne^+e^-. The model is based on an effective field theory approach, incorporating 16 baryon resonances below 2 GeV. Parameters of the model are fitted to pion photoproduction data. We present the resulting dilepton invariant mass spectra for \pi^- p collisions up to sqrt(s)=1.9 GeV center-of-mass collision energy. These results are meant to give predictions for the planned experiments at the HADES spectrometer in GSI, Darmstadt.
120076725
Dependence of multiplicity and rapidity distributions on the number of projectile collisions in 200-GeV/c proton-nucleus interactions
Interactions of 200-GeV/c protons on hydrogen, neon, argon, and xenon were studied with a streamer-chamber spectrometer. The number of projectile collisions inside the nucleus and the number of secondary collisions in the intranuclear cascade were estimated. The dependence of multiplicity and rapidity distributions on the number of projectile collisions was analyzed. The predictions of the additive quark model were found to be in qualitative agreement with the results of the experiment.
188188770
The reaction k+ d ---> k0 p p at 4.6 gev/c
122292810
A total energy trigger at large angles used in a calorimetric study of 150 GeV and 300 GeV pion and proton interactions on hydrogen
Abstract Hard hadronic scattering was studied by selecting 150 GeV and 300 GeV π − p and pp events with large energy in a 240 cell calorimeter covering 45† to 135† in the c.m.s. polar angle and the full 2 π azimuth. A downstream calorimeter measured the remaining energy flow at smaller angles. For large energy deposited in the segmented calorimeter the proton induced cross section drops below the pion induced cross section, as expected in a constituent scattering picture. However, neither a simple energy scaling of the cross section nor a dominant jet structure of the events is observed. No evidence was found for recently proposed higher-twist mechanisms leading to events
122039401
Long-range correlations in hadron-nucleus interactions
An analysis of correlations in rapidity of charged particles produced in proton and antiproton interactions on hydrogen, argon and xenon at 200 GeV is presented. Positive long-range correlations are observed in interactions on heavy targets. The dependence of rapidity correlations between the forward and backward hemisphere on the number of projectile collisions is discussed.
123558617
A study of high transverse energy interactions of 300 GeV pions and protons on hydrogen using a streamer chamber
Abstract High transverse energy π − p and pp interactions at 300 GeV/ c have been studied using a calorimeter-triggered streamer-chamber vertex spectrometer. The data are found to have many of the qualitative features expected from hard-scattering processes, in particular charge correlations with the quark content of the incident hadrons, charge correlations between the highest- p T particles, and back-to-back correlations between the highest- p T particles. However, the data are found not to agree quantitatively with a QCD four-jet model. Nor can they be described by an extrapolation of low- p T processes.