Baryonic screening masses in QCD at high temperature

TL;DR

This study calculates baryonic screening masses in high-temperature QCD using lattice simulations, revealing chiral symmetry restoration and persistent interaction effects up to very high temperatures.

Contribution

It provides the first high-precision lattice QCD results for baryonic screening masses at temperatures up to 160 GeV, including continuum extrapolation and analysis of chiral symmetry restoration.

Findings

Degeneracy of positive and negative parity masses confirms chiral symmetry restoration.

Baryonic masses deviate 4-8% from free theory, indicating persistent interactions.

Interaction effects remain significant even at the highest temperatures studied.

Abstract

We compute the baryonic screening masses with nucleon quantum numbers and its negative parity partner in thermal QCD with $N_f=3$ massless quarks for a wide range of temperatures, from $T \sim 1$ GeV up to $\sim 160$ GeV. The computation is performed by Monte Carlo simulations of lattice QCD with $O(a)$-improved Wilson fermions by exploiting a recently proposed strategy to study non-perturbatively QCD at very high temperature. Very large spatial extensions are considered in order to have negligible finite volume effects. For each temperature we have simulated $3$ or $4$ values of the lattice spacing, so as to perform the continuum limit extrapolation with confidence at a few permille accuracy. The degeneracy of the positive and negative parity-state screening masses, expected from Ward identities associated to non-singlet axial transformations, provides further evidence for the restoration of chiral symmetry in the high temperature regime of QCD. In the entire range of temperatures explored, the baryonic masses deviate from the free theory result, $3 \pi T$, by $4$-$8\%$. The contribution due to the interactions is clearly visible up to the highest temperature considered, and cannot be explained by the expected leading behavior in the QCD coupling constant $g$ over the entire range of temperatures explored.