Phase structure of hot dense QCD by a histogram method

TL;DR

This paper investigates the phase structure of hot dense QCD using lattice simulations and a histogram method, identifying critical surfaces and points as functions of quark mass and chemical potential.

Contribution

It introduces a histogram-based approach to determine the phase transition nature and critical points in QCD at finite temperature and density.

Findings

The critical surface separating first order and crossover transitions is mapped.

The critical point at finite density for two-flavor QCD is identified.

The first order transition region expands with increasing chemical potential in many-flavor QCD.

Abstract

We study the phase structure of QCD at high temperature and density by lattice QCD simulations adopting a histogram method. The quark mass dependence and the chemical potential dependence of the nature of phase transition are investigated focusing on the probability distribution function (histogram). The shape of the distribution function changes with the quark mass and chemical potential. Through the shape of the distribution, the critical surface which separates the first order transition and crossover regions in the heavy quark region is determined for the (2+1)-flavor case. Moreover, we determined the critical point at finite density for two-flavor QCD with an intermediate quark mass, using a Gaussian approximation of the complex phase distribution of the quark determinant. The chemical potential dependence of the critical quark mass is also evaluated in the situation where two light quarks and many massive quarks exist. We find that the first order transition region becomes wider with the chemical potential in the many-flavor QCD.