Baryon-strangeness correlations in Au+Au collisions at s_(NN)~(1/2) = 7.7–200 GeV from the UrQMD model

摘要

Fluctuations and correlations of conserved charges are sensitive observables for studying the QCD phase transition and critical point in high-energy heavy-ion collisions. We have studied the centrality and energy dependence of mixed cumulants (up to fourth order) between net baryon and net strangeness in Au + Au collisions at s_(NN)~(1/2) = 7.7, 11.5, 19.6, 27, 39, 62.4, and 200 GeV from the ultrarelativistic quantum molecular dynamics (UrQMD) model. To compare with other theoretical calculations, we normalize these mixed cumulants by various order cumulants of net-strangeness distributions. We found that the results obtained from UrQMD calculations are comparable with the results from lattice QCD at low temperature and hadron resonance gas model. The ratios of mixed cumulants (R_(11)~(BS) ,R_(13)~(BS) ,R_(22)~(BS) ,R_(31)~(BS)) from UrQMD calculations show weak centrality dependence. However, themixed-cumulant ratios RBS 11 and R_(31)~(BS) show strong increase at low energy, while the R_(13)~(BS) and R_(22)~(BS) are similar at different energies. Furthermore, we have also studied the correlations between different hadron species and their contributions to the net-baryon and net-strangeness correlations. These model studies can provide baselines for searching for the signals of QCD phase transition and critical point in heavy-ion collisions.