Is There a Flavor Hierarchy in the Deconfinement Transition of QCD?

Abstract

We present possible indications for flavor separation during the QCD crossover transition based on continuum extrapolated lattice QCD calculations of higher order susceptibilities. We base our findings on flavor-specific quantities in the light and strange quark sector. We propose a possible experimental verification of our prediction, based on the measurement of higher order moments of identified particle multiplicities. Since all our calculations are performed at zero baryochemical potential, these results are of particular relevance for the heavy-ion program at the LHC.

Hadron yields and the phase diagram of strongly interacting matter

“…Since the transition from the deconfined medium to hadronic matter is a smooth crossover, the freeze-out temperature cannot be uniquely identified but it depends on the observable under study. It was further suggested in [58], based on lattice and Hadron Resonance Gas (HRG) calculations, that the (crossover) transition temperature for light and strange quarks may be different (150 MeV and 165 MeV, respectively). This would subsequently lead to a separate freeze-out at slightly lower temperatures.…”

Strangeness at Intermediate Baryon Density

“…This is indicative of a separation of chemical freeze-out temperatures between light and strange quark hadrons. Since the ALICE results came from Pb+Pb collisions at √ s NN = 2.7 TeV, the µ B was nearly 0 and the results are suited for comparisons with lattice QCD calculations of higher order quark number susceptibilities χ n [12][13][14] for light and strange quarks [15]. Figure 1 (right panel) shows the dependency of the susceptibility ratios χ 4 /χ 2 for light and strange quarks on temperature T together with corresponding HRG model predictions.…”

“…The lattice data are compared to HRG calculations. Left panel taken from Ref [9] and right panel from Ref [15].…”

Strangeness in Quark Matter: Opening Talk

“…The enhancement of strange particle production is discussed [5,6,7,8,9] as a possible signal for the creation of a deconfined phase. Recently several observables, regarding strange and charm quarks have shown the importance of understanding the dynamics of strangeness and charm production in heavy ion collisions:• Strange particle ratios and yields from the ALICE collaboration may indicate that there is either no unique chemical freeze out point for strange an non-strange particles [10,11,12,13], or the light quark phase space is severely over-saturated [14].• Lattice calculations on the stability of the H-dibaryon indicate it might be either very loosely bound or a resonant state [15,16,17].• Viscous hydrodynamics, with fluctuating initial conditions [18] and finite but small viscous corrections, seems to describe strange hadron observables even at large baryon densities [19,20].• The hydrodynamic model calculations show sensitivity on the life time of the system and the applied equation of state [21].• There are indications that systems created in high energy p+p and p+Pb collisions can thermalize/equilibrate to a certain degree and show signs of collectivity [22,23,24,25].• A polarization of Λ's due to the finite angular momentum of the fireball is expected [26]. …”

“…• Strange particle ratios and yields from the ALICE collaboration may indicate that there is either no unique chemical freeze out point for strange an non-strange particles [10,11,12,13], or the light quark phase space is severely over-saturated [14].…”