The order of the chiral transition in N_f=2 QCD

TL;DR

This paper investigates the nature of the chiral transition in two-flavor QCD using finite size scaling and lattice simulations, finding evidence inconsistent with second order but compatible with a first order transition.

Contribution

The study develops a finite size scaling strategy and provides numerical evidence supporting a first order chiral transition in N_f=2 QCD.

Findings

Second order O(4) transition is excluded.

Data are consistent with a first order transition.

Numerical simulations on various lattice sizes support the conclusion.

Abstract

A strategy is developed to investigate the order of the transition using finite size scaling and its relation to color confinement. An in-depth numerical investigation has been performed with KS fermions on lattices with N_t=4 and N_s=12,16,20,24,32 and quark masses am_q ranging from 0.01335 to 0.35. The specific heat and a number of susceptibilities have been measured and compared with the expectation of an O(4) second order and a first order phase transition. A second order O(4) is excluded, whilst data are consistent with a first order.