Freeze-out conditions from net-proton and net-charge fluctuations at RHIC

Abstract

We calculate ratios of higher-order susceptibilities quantifying fluctuations in the number of netprotons and in the net-electric charge using the Hadron Resonance Gas (HRG) model. We take into account the effect of resonance decays, the kinematic acceptance cuts in rapidity, pseudo-rapidity and transverse momentum used in the experimental analysis, as well as a randomization of the isospin of nucleons in the hadronic phase. By comparing these results to the latest experimental data from the STAR Collaboration, we determine the freeze-out conditions from net-electric charge and net-proton distributions and discuss their consistency.

Fluctuations of conserved charges within a Hadron Resonance Gas approach: chemical freeze-out conditions from net-charge and net-proton fluctuations

“…LQCD studies of the deconfinement transition from quarks and gluons to hadrons, also show a similar flavour hierarchy [27]. In [10] we reproduce quite well the STAR data on particle ratios for √ s = 200 GeV, but hyperons are underestimated for our value of T ch . However the discussion on the so-called proton anomaly is still ongoing.…”

“…In order to make connection to experimental data which cover a finite phase space region, we also include the experimental kinematic cuts on transverse momentum, rapidity and pseudo-rapidity which modifies the thermodynamical integrals in the HRG calculations [10].…”

“…The net-electric charge fluctuations are not affected by this issue since data and our calculations are based on the contribution from pions, kaons and protons which constitute the most abundant charged particles. More details can be found in our published work [10,11].…”

“…So far, these freeze-out parameters have been extracted by means of Statistical Hadronization Models (SHMs) which fitted the data on particle yields and ratios in a wide range of energies, from AGS to LHC [1][2][3][4][5]. Recently the study of fluctuations of conserved charges in Lattice QCD (LQCD) [6][7][8][9] approach [10][11][12][13][14][15] has been proposed as another tool to obtain the values of the freeze-out parameters and experimental data for these observables have been published by the STAR collaboration [16,17]. The description of the low temperature regime of strongly interacting matter within a HRG model shows a nice agreement with LQCD calculations up to T ≈ 170 MeV, near the crossover region [18,19].…”

Frontiers of finite temperature lattice QCD

“…This is a generalization of the earlier statistical hadronization model, which was based on particle yields instead of fluctuations [23,24]. The fluctuation-based freeze-out temperatures lie in general below the original yield-based freeze-out curve [25].…”