Proton intermittency in heavy-ion collisions



    • 3:00 PM 3:15 PM
      Summary of NA61/SHINE results on proton intermittency 15m

      Local proton density fluctuations in transverse momentum space represent an order parameter of the chiral phase transition and are expected to scale according to a universal power-law in the vicinity of the CP. The NA61/SHINE experiment intermittency analysis program probes the second scaled factorial moments (SSFMs) $F_2(M)$ of proton momenta at mid-rapidity. A number of collision systems of different size (Be+Be, Ar+Sc, Pb+Pb) are analyzed, at the maximum SPS energy ($\sqrt{s_{NN}} \sim 17$ GeV), yielding a non-trivial intermittency effect in the Ar+Sc system. Novel techniques, such as the statistical bootstrap, cumulative variables and independent bin analysis, are implemented in order to quantify statistical and systematic uncertainties, whereas the observed effect is compared against Monte Carlo models.

      Speaker: Nikolaos Davis (Polish Academy of Sciences (PL))
    • 3:15 PM 3:45 PM
      Intermittency analysis of proton numbers in heavy-ion collisions at RHIC energies 30m

      Jin Wu, Yufu Lin, Zhiming Li, Xiaofeng Luo, Yuanfang Wu

      Local density fluctuation near the QCD critical point has been suggested to exhibit a power-law behavior which can be probed by an intermittency analysis on scaled factorial moment (SFM) in relativistic heavy-ion collisions. The collision energy and centrality dependence of the second-order SFMs are systematically investigated in Au + Au collisions at √sNN = 7.7, 11.5, 19.6, 27, 39, 62.4, 200 GeV within the UrQMD model. We estimate the non-critical background in the measurement of intermittency and suggest a cumulative variable method to effectively remove the contributions from background. We further study the effect of particle detection efficiency by implementing UrQMD events in the RHIC/STAR experimental tracking efficiencies. A cell-by-cell method is proposed for experimental application of efficiency corrections on SFM. This work can provide a guidance of background subtraction and efficiency correction for experimental measurement of intermittency in the search of QCD critical point in heavy-ion collisions.

      Speaker: Zhiming Li (Central China Normal University)
    • 3:45 PM 4:15 PM
      Proton correlations and apparent intermittency in the UrQMD model with hadronic potentials 30m

      Pengcheng Li, Yongjia Wang, Jan Steinheimer, Qingfeng Li, Hongfei Zhang

      It is shown that the inclusion of hadronic interactions, and in particular nuclear potentials, in simulations of heavy ion collisions at the SPS energy range can lead to obvious correlations of protons. These correlations contribute significantly to an intermittency analysis as performed at the NA61 experiment. The beam energy and system size dependence is studied by comparing the resulting intermittency index for heavy ion collisions of different nuclei at beam energies of 40A, 80A and 150A GeV. The resulting intermittency index from our simulations is similar to the reported values of the NA61 collaboration, if nuclear interactions are included. The observed apparent intermittency signal is the result of the correlated proton pairs with small relative transverse momentum Δpt, which would be enhanced by hadronic potentials, and this correlation between the protons is slightly influenced by the coalescence parameters and the relative invariant four-momentum qinv cut.

      Speaker: Pengcheng Li
    • 4:15 PM 4:45 PM
      Common discussion 30m