Fermions obstruct dimensional reduction in hot QCD

TL;DR

This study investigates how non-perturbative effects in hot QCD with light quarks prevent the expected dimensional reduction at high temperatures, impacting theoretical predictions relevant for collider experiments.

Contribution

First analysis of glueball-like screening masses in four-flavor QCD at high temperatures, revealing non-perturbative effects obstructing dimensional reduction.

Findings

Glueball screening masses are heavier than pion-like and sigma-like masses.

Pion-like and sigma-like screening masses are degenerate across the studied temperature range.

Obstruction to dimensional reduction may persist at temperatures achievable at the LHC.

Abstract

We have studied, for the first time, screening masses obtained from glueball-like correlators in Quantum Chromodynamics with four light dynamical flavours of quarks in the temperature range 1.5T_c < T < 3T_c, where T_c is the temperature at which the chiral transition occurs. We have also studied pion-like and sigma-like screening masses, and found that they are degenerate in the entire range of T. These obstruct perturbative dimensional reduction since the lowest glueball screening mass is heavier than them. Extrapolation of our results suggests that this obstruction may affect the entire range of temperature expected to be reached even at the Large Hadron Collider.