Thermodynamics of lattice QCD with 3 flavours of colour-sextet quarks

TL;DR

This study investigates the phase transitions in lattice QCD with 3 colour-sextet quarks to determine if it exhibits conformal behavior or QCD-like properties, comparing results with the 2-flavour case.

Contribution

The paper provides the first finite-temperature lattice QCD results for 3-flavour colour-sextet quarks, analyzing their phase transitions and comparing with the 2-flavour case to understand conformality.

Findings

Deconfinement and chiral-symmetry restoration transitions occur at weaker couplings as $N_t$ increases.

Transitions are in the strong-coupling domain, indicating the theory is essentially quenched.

Similar phase structures observed in 2 and 3-flavour theories.

Abstract

We have been studying QCD with 2 flavours of colour-sextet quarks to distinguish whether it is QCD-like or conformal. For comparison we are now studying QCD with 3 flavours of colour-sextet quarks, which is believed to be conformal in the chiral limit. Here we present the results of simulations of lattice QCD with 3 colour-sextet quarks at finite temperatures on lattices of temporal extent $N_t=4$ and 6, with masses small enough to yield access to the chiral limit. As for the 2-flavour case, we find well-separated deconfinement and chiral-symmetry restoration transitions, both of which move to appreciably weaker couplings as $N_t$ is increased from 4 to 6. If this theory is conformal, we would expect there to be a bulk chiral transition at a fixed coupling. For this reason we conclude that for $N_t=4$ and 6, the chiral and hence the deconfinement transitions are in the strong-coupling domain where the theory is essentially quenched. The similarity between the behaviours of the 2 and 3 flavour theories suggested that the $N_t=4$ and 6 transitions for the 2-flavour theory also lie in the strong-coupling domain. The phase structure of both theories is very similar.