Study of QCD critical point using the canonical ensemble method

TL;DR

This study uses lattice simulations with the canonical ensemble method to explore the QCD phase diagram, identifying signals of phase transitions and estimating the critical point location at finite baryon density and temperature.

Contribution

First application of canonical ensemble lattice simulations to locate the QCD critical point, providing preliminary results and phase boundary analysis.

Findings

Clear signal of first order phase transition in four-flavor QCD.

No transition observed in two-flavor QCD at low temperatures.

Identification of phase boundaries using Maxwell construction.

Abstract

The existence of the QCD critical point at non-zero baryon density is not only of great interest for experimental physics but also a challenge for the theory. Any hint of the existence of the first order phase transition and, particularly, its critical point will be valuable towards a full understanding of the QCD phase diagram. We use lattice simulation based on the canonical ensemble method to explore the finite baryon density and finite temperature region and look for the QCD critical point. As a benchmark, we run simulations for the four degenerate flavor QCD where we observe a clear signal of the expected first order phase transition. In the two flavor case, we do not see any signal for temperatures as low as $0.83 \rm{T_c}$. Although our real world contains two light quarks and one heavier quark, three degenerate flavor case shares a lot of similar phase structures as the QCD. We scan the phase diagram using clover fermions with $m_\pi \approx 700{MeV}$ on $6^3\times4$ lattices. The baryon chemical potential is measured as we increase the baryon number and we see the characteristic "S-shape" that signals the first order phase transition. We determine the phase boundaries by Maxwell construction and report our preliminary results for the location of critical point for the present lattice.