A dynamical holographic QCD model for spontaneous chiral symmetry breaking and confinement

TL;DR

This paper develops a holographic QCD model that captures spontaneous chiral symmetry breaking and confinement, reproducing meson spectra and decay constants consistent with QCD phenomenology.

Contribution

It introduces a novel 5d Einstein-dilaton holographic model with a non-minimal dilaton coupling, enabling the study of chiral symmetry breaking and meson spectra.

Findings

Reproduces confining quark-antiquark potential.

Identifies a massless pion in the chiral limit.

Matches the Gell-Mann-Oakes relation for pions.

Abstract

In this paper, we present a holographic realization of spontaneous chiral symmetry breaking and confinement. The latter is realized by building a solution of 5d Einstein-dilaton gravity leading to a confining quark antiquark potential. The 4d currents and the quark mass operator associated with chiral symmetry breaking and creation of meson states are mapped to 5d fields whose dynamics is given by a non-Abelian Higgs action. We introduce a non-minimal dilaton coupling to the tachyon potential which has two parameters, one of them controlling the presence or absence of spontaneous chiral symmetry breaking and the other controlling the sign of the chiral condensate as the quark mass grows. We calculate the masses of vector, scalar, axial-vector and pseudoscalar mesons, focusing on the effect of chiral symmetry breaking on the spectrum. In the chiral limit we identify the emergence of a massless state in the pseudoscalar meson spectrum, i.e., the pion. We calculate all meson decay constants and confirm that the pion satisfies the Gell-Mann-Oakes relation in the light quark regime.