Rapidity and energy dependence of the electric charge correlations inA+Acollisions from20Ato158A

Abstract

Results from electric charge correlations studied with the Balance Function method in A+A collisions from 20A to 158A GeV are presented in two different rapidity intervals: In the mid-rapidity region we observe a decrease of the width of the Balance Function distribution with increasing centrality of the collision, whereas this effect vanishes in the forward rapidity region.Results from the energy dependence study in central Pb+Pb collisions show that the narrowing of the Balance Function expressed by the normalised width parameter W increases with energy towards the highest SPS and RHIC energies.Finally we compare our experimental data points with predictions of several models. The hadronic string models UrQMD and HIJING do not reproduce the observed narrowing of the Balance Function. However, AMPT which contains a quark-parton transport phase before hadronization can reproduce the narrowing of the BF's width 2 with centrality. This confirms the proposed sensitivity of the Balance Function analysis to the time of hadronization.

Balance functions fromAu+Au,d+Au, andpAggarwal1, Ahammed2, Alakhverdyants3 et al. 2010Phys. Rev. CSelf Cite541340View full textAdd to dashboardCite

“…The rapidity dependence and incident energy dependence of the balance function for all charged particles have been studied for Pb + Pb collisions from √ s NN = 6.3 GeV to √ s NN = 17.3 GeV in Ref. [35]. The balance function is observed to narrow in central collisions for midrapidity, but does not narrow at forward rapidity.…”

“…The authors of Ref. [35] show that the narrowing of the balance function in terms of η in central collisions can be explained with the AMPT (a multiphase transport) model [36] incorporating delayed hadronization, while models such as HIJING (heavy ion jet interaction generator, version 1.38) [37] and UrQMD fail to reproduce the observed narrowing. We have recently presented a study of the longitudinal scaling of the balance function in Au + Au collisions at √ s NN = 200 GeV [38].…”

Beam-energy dependence of charge balance functions from Au + Au collisions at energies available at the BNL Relativistic Heavy Ion Collider

“…The balance function for all charged particles narrows in central Pb + Pb collisions at 17.3 GeV and the widths of the balance functions for p + p, C + C, Si + Si, and Pb + Pb collisions scale with the number of participating nucleons. The NA49 Collaboration has also published results [37] for the rapidity dependence and beam energy dependence of the balance function for all charged particles for Pb + Pb collisions from √ s NN = 6.3 to 17.3 GeV. The balance function was observed to narrow in central collisions for midrapidity, but did not narrow at forward rapidity.…”

“…[43] calculated the widths over the range 0.0 η 1.6 for both the ALICE and STAR balance functions. We do not compare with the results from NA49 [37] here because the acceptance of NA49 in η is relatively small.…”

“…The authors of Ref. [37] showed that the narrowing of the balance function in terms of η in central collisions was explained with the AMPT (a multiphase transport) model [38] incorporating delayed hadronization, while models such as HIJING (heavy ion jet interaction generator, version 1.38, default parameters) [39] and UrQMD (ultrarelativistic quantum molecular dynamics, version 3.3, with default parameters) [40] [23,42]. The balance functions for all charged particles and for charged pions narrow as the events become more central while balance functions calculated using HIJING and UrQMD showed no centrality dependence.…”