QCD Thermodynamics with Three Flavors of Improved Staggered Quarks

TL;DR

This study investigates QCD thermodynamics with three flavors of improved staggered quarks, revealing a rapid crossover and providing the first calculations of quark number susceptibilities relevant for heavy ion collision experiments.

Contribution

It introduces simulations of three-flavor QCD thermodynamics using improved actions and presents the first quark number susceptibility calculations with three sea quark flavors.

Findings

Observed a rapid crossover instead of a phase transition.

Calculated quark number susceptibilities close to continuum values.

Results are relevant for heavy ion collision experiments.

Abstract

We report on a study of QCD thermodynamics with three flavors of quarks, using a Symanzik improved gauge action and the Asqtad O(a^2) improved staggered quark action. Simulations were carried out with lattice spacings 1/4T, 1/6T and 1/8T both for three degenerate quarks with masses less than or equal to the strange quark mass, m_s, and for degenerate up and down quarks with masses in the range 0.1 m_s \leq m_{u,d} \leq 0.6 m_s, and the strange quark mass fixed near its physical value. We present results for standard thermodynamics quantities, such as the Polyakov loop, the chiral order parameter and its susceptibility. For the quark masses studied to date we find a rapid crossover rather than a bona fide phase transition. We have carried out the first calculations of quark number susceptibilities with three flavors of sea quarks. These quantities are of physical interest because they are related to event-by-event fluctuations in heavy ion collision experiments. Comparison of susceptibilities at different lattice spacings show that our results are close to the continuum values.