Net-baryon Rapidity Distributions Research Articles

Landau and Eckart frames for relativistic fluids in nuclear collisions

The quark matter created in relativistic nuclear collisions is interpreted as a nearly-perfect fluid. The recent efforts to explore its finite-density properties in the beam energy scan programs motivate one to revisit the issue of the local rest frame fixing in off-equilibrium hydrodynamics. I first investigate full second-order relativistic hydrodynamics in the Landau and the Eckart frames. Then numerical hydrodynamic simulations are performed to elucidate the effect of frame choice on flow observables in relativistic nuclear collisions. The results indicate that the flow can differ in the Landau and the Eckart frames but charged particle and net baryon rapidity distributions are mostly frame independent when off-equilibrium kinetic freeze-out is considered.

Dynamical initial-state model for relativistic heavy-ion collisions

We present a fully three-dimensional model providing initial conditions for energy and net-baryon density distributions in heavy ion collisions at arbitrary collision energy. The model includes the dynamical deceleration of participating nucleons or valence quarks, depending on the implementation. The duration of the deceleration continues until the string spanned between colliding participants is assumed to thermalize, which is either after a fixed proper time, or a fluctuating time depending on sampled final rapidities. Energy is deposited in space-time along the string, which in general will span a range of space-time rapidities and proper times. We study various observables obtained directly from the initial state model, including net-baryon rapidity distributions, 2-particle rapidity correlations, as well as the rapidity decorrelation of the transverse geometry. Their dependence on the model implementation and parameter values is investigated. We also present the implementation of the model with 3+1 dimensional hydrodynamics, which involves the addition of source terms that deposit energy and net-baryon densities produced by the initial state model at proper times greater than the initial time for the hydrodynamic simulation.

Dissipative hydrodynamic effects on the quark-gluon plasma at finite baryon density

The quark-gluon plasma behaves as a relativistic viscous fluid in high-energy heavy ion collisions. I develop a causal dissipative hydrodynamic model at finite baryon density for RHIC and LHC to estimate the net baryon rapidity distribution. The net baryon number is found to be carried to forward rapidity by the flow, effectively enhancing the transparency of the collisions. This suggests that the energy available for the production of a hot medium could be larger than that naively implied from experimental data. Also the distribution can be sensitive to baryon dissipation as much as to shear and bulk viscosity.

Gluon Saturation Model with Geometric Scaling for Net-Baryon Distributions in Relativistic Heavy Ion Collisions

The net-baryon number is essentially transported by valence quarks that probe the saturation regime in the target by multiple scattering. The net-baryon distributions, nuclear stopping power and gluon saturation features in the SPS and RHIC energy regions are investigated by taking advantage of the gluon saturation model with geometric scaling. Predications are made for the net-baryon rapidity distributions, mean rapidity loss and gluon saturation features in central Pb + Pb collisions at LHC.

Net-Baryon and Net-Kaon Rapidity Distributions in Ultrarelativistic Heavy-Ion Collisions

In this paper, the gluon distribution is extracted from the KLR-AdS/CFT saturation model and used to investigate net-baryon and net-kaon rapidity distributions in ultrarelativistic heavy-ion collisions. With the same parameters of the saturation model fitting to HERA data and an χ2 analysis of the overall constant C, the theoretical results are in good agreement with RHIC data in Au+Au collisions at √s = 0.2 TeV. Then, we present the predictive results for net-baryon rapidity distributions in central Pb+Pb collisions at LHC energies of √s = 2.76, 3.94, and 5.52 TeV, and give the corresponding values of dN/dy for net-baryon at y = 0.

Gluon saturation and baryon stopping in the SPS, RHIC, and LHC energy regions

A new geometrical scaling method with a gluon saturation rapidity limit is proposed to study the gluon saturation feature of the central rapidity region of relativistic nuclear collisions. The net-baryon number is essentially transported by valence quarks that probe the saturation regime in the target by multiple scattering. We take advantage of the gluon saturation model with geometric scaling of the rapidity limit to investigate net baryon distributions, nuclear stopping power and gluon saturation features in the SPS and RHIC energy regions. Predictions for net-baryon rapidity distributions, mean rapidity loss and gluon saturation feature in central Pb+Pb collisions at the LHC are made in this paper.

Baryon stopping probes geometric scaling

We investigate baryon transport in relativistic heavy-ion collisions at energies reached at SPS, RHIC and LHC in the model of saturation. An analytical scaling law is derived within the color glass condensate framework based on small-coupling QCD. Transverse momentum spectra, net-baryon rapidity distributions and their energy, mass and centrality dependences are well described. In a comparison with RHIC data in Au + Au collisions at s N N = 62.4 GeV and 200 GeV, the gradual approach to the gluon saturation regime is investigated, and limits for the saturation-scale exponent are determined. Predictions for net-baryon rapidity spectra and the mean rapidity loss in central Pb + Pb collisions at LHC energies of s N N = 5.52 TeV are made.

Baryon stopping and saturation physics in relativistic collisions

We investigate baryon transport in relativistic heavy-ion collisions at energies reached at the CERN Super Proton Synchrotron, BNL Relativistic Heavy-Ion Collider (RHIC), and CERN LHC in the model of saturation. An analytical scaling law is derived within the color glass condensate framework based on small-coupling QCD. Transverse momentum spectra, net-baryon rapidity distributions and their energy, mass and centrality dependences are well described. In a comparison with RHIC data in Au + Au collisions at sqrt (s_NN) = 62.4 GeV and 200 GeV, the gradual approach to the gluon saturation regime is investigated, and limits for the saturation-scale exponent are determined. Predictions for net-baryon rapidity spectra and the mean rapidity loss in central Pb + Pb collisions at LHC energies of sqrt (s_NN) = 5.52 TeV are made.

Baryon Stopping as a New Probe of Geometric Scaling

We suggest using net-baryon rapidity distributions in central relativistic heavy-ion collisions at energies reached at the CERN Super Proton Synchrotron, BNL Relativistic Heavy-Ion Collider (RHIC), and CERN LHC in order to probe saturation physics. Within the color glass condensate framework based on small-coupling QCD, net-baryon rapidity distributions are shown to exhibit geometric scaling. In a comparison with RHIC data in Au+Au collisions at sqrt[sNN=62.4 GeV and 200 GeV the gradual approach to the gluon saturation regime is investigated. Predictions for net-baryon rapidity spectra and the mean rapidity loss in central Pb+Pb collisions at LHC energies of sqrt[sNN=5.52 TeV are made.

Diffusion and local deconfinement in relativistic systems

In relativistic heavy-ion systems at the highest collision energies, new deconfinement signatures emerge and indicate an increasingly clear separation between soft hadronic processes and hard partonic interactions in a locally deconfined subsystem. Here the emphasis is on longitudinal variables, namely, net-baryon rapidity distributions. As described in a Relativistic Diffusion Model, they change from bell shaped at the lower to double humped at the higher SPS energy, but do not reach local statistical equilibrium. At $\sqrt{{s}_{NN}}=200\phantom{\rule{0.3em}{0ex}}\text{GeV}$ in the Au-Au system, however, they are shown to consist of three components. In addition to the nonequilibrium contributions, a third fraction close to midrapidity containing ${Z}_{eq}\ensuremath{\simeq}22$ protons reaches local statistical equilibrium in a discontinuous transition. It may be associated with a deconfinement of the participant partons and thus, serve as a signature for quark-gluon matter formation.

Anomalous net-baryon-rapidity spectra at RHIC

Net-baryon rapidity distributions in central Au+Au collisions at sNN=200 GeV are shown to consist of three components. The nonequilibrium contributions are accounted for in a Relativistic Diffusion Model. Near midrapidity, a third fraction containing Zeq≃22 protons reaches local statistical equilibrium in a discontinuous transition. It may be associated with a deconfinement of the participant partons and thus, serve as a signature for Quark–Gluon Matter formation.

Net baryon density in Au+Au collisions at the relativistic heavy ion collider.

We calculate the net-baryon rapidity distribution in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) in the framework of the parton cascade model (PCM). Parton rescattering and fragmentation leads to a substantial increase in the net-baryon density at midrapidity over the density produced by initial primary parton-parton scatterings. The PCM is able to describe the measured net-baryon density at RHIC.

Monte Carlo model for multiparticle production at ultrarelativistic energies.

The Monte Carlo parton string model for multiparticle production in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions at high energies is described. An adequate choice of the parameters in the model gives the possibility of recovering the main results of the dual parton model, with the advantage of treating both hadron and nuclear interactions on the same footing, reducing them to interactions between partons. Also the possibility of considering both soft and hard parton interactions is introduced. Comparison to the available experimental data on nucleon and nuclear collisions, together with predictions for mean multiplicities, net baryon rapidity distributions, and the temporal evolution of meson densities for heavy ion collisions at the CERN Super Proton Synchrotron (194A) GeV) and the BNL Relativistic Heavy Ion Collider (200A GeV) are presented. Furthermore, predictions for charm production at these energies are given.