Nonperturbative investigations of SU(3) gauge theory with eight dynamical flavors

TL;DR

This study investigates the nonperturbative properties of SU(3) gauge theory with eight flavors using lattice simulations, focusing on chiral symmetry breaking and scalar spectrum, and compares it to four-flavor theory to understand different dynamical behaviors.

Contribution

It provides the first detailed lattice analysis of SU(3) with eight flavors, highlighting challenges in confirming chiral symmetry breaking and examining the scalar spectrum in this regime.

Findings

Light flavor-singlet scalar degenerate with pseudo-Goldstone states

Finite-temperature transitions enter a strongly coupled phase at small fermion masses

Contrast between 8-flavor and 4-flavor theories in scalar spectrum behavior

Abstract

We present our lattice studies of SU(3) gauge theory with $N_f$ = 8 degenerate fermions in the fundamental representation. Using nHYP-smeared staggered fermions we study finite-temperature transitions on lattice volumes as large as $L^3 \times N_t = 48^3 \times 24$, and the zero-temperature composite spectrum on lattice volumes up to $64^3 \times 128$. The spectrum indirectly indicates spontaneous chiral symmetry breaking, but finite-temperature transitions with fixed $N_t \leq 24$ enter a strongly coupled lattice phase as the fermion mass decreases, which prevents a direct confirmation of spontaneous chiral symmetry breaking in the chiral limit. In addition to the connected spectrum we focus on the lightest flavor-singlet scalar particle. We find it to be degenerate with the pseudo-Goldstone states down to the lightest masses reached so far by non-perturbative lattice calculations. Using the same lattice approach, we study the behavior of the composite spectrum when the number of light fermions is changed from eight to four. A heavy flavor-singlet scalar in the 4-flavor theory affirms the contrast between QCD-like dynamics and the low-energy behavior of the 8-flavor theory.