Charged particle rapidity distributions at relativistic energies

Abstract

Using a multiphase transport model ͑AMPT͒, which includes both initial partonic and final hadronic interactions, we study the rapidity distributions of charged particles such as protons, antiprotons, pions, and kaons in heavy ion collisions at RHIC. The theoretical results for the total charged particle multiplicity at midrapidity are consistent with those measured by the PHOBOS Collaboration in central AuϩAu collisions at ͱsϭ56 and 130 A GeV. We find that these hadronic observables are much more sensitive to the hadronic interactions than to the partonic interactions. DOI: 10.1103/PhysRevC.64.011902 PACS number͑s͒: 25.75.Ϫq, 24.10.Lx Collisions of nuclei at high energies offer the possibility to subject nuclear matter to the extreme conditions of large compression and high excitation energies. Studies based on both nonequilibrium transport models ͓1͔ and equilibrium thermal models ͓2͔ have shown that the experimental data from heavy ion collisions at SIS, AGS, and SPS, where the center of mass collision energies are, respectively, about 3, 5, and 17 A GeV, are consistent with the formation of a hot dense nuclear matter in the initial stage of collisions. With the Relativistic Heavy Ion Collider ͑RHIC͒ at Brookhaven National Laboratory, which can reach a center-of-mass energy of 200A GeV, the initial energy density is expected to exceed that for the transition from the hadronic matter to the quark-gluon plasma. Experiments at RHIC thus provide the opportunity to recreate the matter which is believed to have existed during the first microsecond after the big bang and to study its properties.Recently, charged particle multiplicity near midrapidity has been measured in central AuϩAu collisions at ͱsϭ56and 130 A GeV at RHIC by the PHOBOS Collaboration ͓3͔. The observed charged particle density per participant is found to be compatible with the predictions of the HIJING model that includes particle production from minijets produced in hard-scattering processes ͓4͔. Although the HIJING model implements the parton energy loss via jet quenching ͓5͔, it does not include explicit interactions among minijet partons and the final-state interactions among hadrons. Other models have also been used to understand the data from the PHOBOS Collaboration. The LEXUS model ͓6͔, which is based on a linear extrapolation of ultrarelativistic nucleonnucleon scattering to nucleus-nucleus collisions, predicts too many charged particles compared with the PHOBOS data ͓7͔. On the other hand, the hadronic cascade model LUCIFER ͓8͔ predicts a charged particle multiplicity near midrapidity that is comparable to the PHOBOS data ͓9͔. In this Rapid Communication, we shall use a multiphase transport model ͑AMPT͒ ͓10͔, that includes both partonic and hadronic interactions, to study their effects not only on the total charged particle multiplicity but also on those of kaons, protons, and antiprotons. In the AMPT model, the initial conditions are obtained from the HIJING model ͓4͔ by using a Woods-Saxon radial shape for the colliding nuclei and in...

Higher harmonic flow coefficients of identified hadrons in Pb-Pb collisions at s N N = 2.76 $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV

“…Section 6.3 presents the mass dependence of v sub n (p T ) which is followed by a discussion about the scaling properties of different flow harmonics in different centrality intervals. In section 6.5, two models, namely iEBE-VISHNU [49] and A Multi Phase Transport model (AMPT) [50][51][52], are compared with the experimental measurements. Note that the same data will be shown in different representations in the following sections to highlight the various physics implications of the measurements.…”

Anisotropic flow inCu+Aucollisions atsNN=200GeV

“…Final-state scatterings among hadrons are then modeled by a relativistic transport (ART) model [31]. The default AMPT model [20] has been quite successful in describing measured rapidity distributions of charge particles, particle to antiparticle ratios, and spectra of low transverse momentum pions and kaons [21] in heavy-ion collisions at the Super Proton Synchrotron (SPS) and RHIC. It has also been useful in understanding the production of J /ψ [25] and multistrange baryons [26] in these collisions.…”

“…The AMPT model [20,21,[25][26][27]] is a hybrid model that uses minijet partons from hard processes and strings from soft processes in the Heavy Ion Jet Interaction Generator (HIJING) model [28] as the initial conditions for modeling heavy-ion collisions at ultra-relativistic energies. The time evolution of resulting minijet partons is described by Zhang's parton cascade (ZPC) [29] model.…”

“…In the present work, we use a multiphase transport (AMPT) model, which includes both initial partonic and final hadronic interactions [20,21], to study the anisotropic flows v 1 , v 2 , v 3 , and v 4 of charged hadrons in asymmetric Cu + Au collisions at √ s = 200A GeV at RHIC. Use is made of both the default version and the version with string melting, that is, a version allowing hadrons that are expected to be formed from initial strings to convert to their valence quarks and antiquarks [10,22,23].…”

Hadron production from resonance decay in relativistic collisions

“…Large fractions of final light-particles within those thermodynamic equilibrium models result from secondary decays of heavy resonances whose features are, generally, less and less known the heavier the resonances. The lack of knowledge has forced the use of cut-offs on the primary resonance mass in equilibrium models [3,4,5,6]; analogous cut-offs have been employed in transport models [9,10,11]. In this paper, we explore the possibility of an apparent equilibrium in the reactions stemming from sequential binary decays of heavy resonances, with the characteristic temperature describing the resonance mass spectrum, rather than being proposed ad hoc.…”