title: Freeze-out conditions in heavy ion collisions from QCD thermodynamics.
abstract: We present a determination of freeze-out conditions in heavy ion collisions based on ratios of cumulants of net electric charge fluctuations. These ratios can reliably be calculated in lattice QCD for a wide range of chemical potential values by using a next-to-leading order Taylor series expansion around the limit of vanishing baryon, electric charge and strangeness chemical potentials. From a computation of up to fourth order cumulants and charge correlations we first determine the strangeness and electric charge chemical potentials that characterize freeze-out conditions in a heavy ion collision and confirm that in the temperature range 150 MeV ≤ T ≤ 170 MeV the hadron resonance gas model provides good approximations for these parameters that agree with QCD calculations on the 5%-15% level. We then show that a comparison of lattice QCD results for ratios of up to third order cumulants of electric charge fluctuations with experimental results allows us to extract the freeze-out baryon chemical potential and the freeze-out temperature.
authors.affiliation: Physics Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: A
authors.initials: A
authors.lastname: Bazavov
authors.forename: H-T
authors.initials: HT
authors.lastname: Ding
authors.forename: P
authors.initials: P
authors.lastname: Hegde
authors.forename: O
authors.initials: O
authors.lastname: Kaczmarek
authors.forename: F
authors.initials: F
authors.lastname: Karsch
authors.forename: E
authors.initials: E
authors.lastname: Laermann
authors.forename: Swagato
authors.initials: S
authors.lastname: Mukherjee
authors.forename: P
authors.initials: P
authors.lastname: Petreczky
authors.forename: C
authors.initials: C
authors.lastname: Schmidt
authors.forename: D
authors.initials: D
authors.lastname: Smith
authors.forename: W
authors.initials: W
authors.lastname: Soeldner
authors.forename: M
authors.initials: M
authors.lastname: Wagner