Thermodynamics of Two Flavor QCD to Sixth Order in Quark Chemical Potential

TL;DR

This study computes high-order derivatives of the QCD partition function to explore thermodynamic properties and phase transitions, including the chiral critical point, using lattice simulations with improved staggered fermions.

Contribution

It provides sixth-order Taylor expansion results of QCD thermodynamics at finite chemical potential, advancing understanding of the QCD phase diagram and critical phenomena.

Findings

Bulk thermodynamic observables do not show direct evidence of a chiral critical point.

Results align with high-temperature perturbation theory and hadron resonance gas models.

Analysis of fluctuations and convergence radius relates to phase transition characteristics.

Abstract

We present results of a simulation of 2-flavor QCD on a 4x16^3 lattice using p4-improved staggered fermions with bare quark mass m/T=0.4. Derivatives of the thermodynamic grand canonical partition function Z(V,T,mu_u,mu_d) with respect to chemical potentials mu_(u,d) for different quark flavors are calculated up to sixth order, enabling estimates of the pressure and the quark number density as well as the chiral condensate and various susceptibilities as functions of mu_q = (mu_u + mu_d)/2 via Taylor series expansion. Furthermore, we analyze baryon as well as isospin fluctuations and discuss the relation between the radius of convergence of the Taylor series and the chiral critical point in the QCD phase diagram. We argue that bulk thermodynamic observables do not, at present, provide direct evidence for the existence of a chiral critical point in the QCD phase diagram. Results are compared to high temperature perturbation theory as well as a hadron resonance gas model.