Light scalar mesons in the soft-wall model of AdS/QCD

TL;DR

This paper models light scalar mesons using the soft-wall AdS/QCD approach, achieving compatible masses and decay constants, and explores their organization in Regge trajectories, but finds discrepancies in coupling strengths related to chiral symmetry breaking.

Contribution

It applies the soft-wall AdS/QCD model to light scalar mesons, providing mass spectra, decay constants, and insights into their organization and couplings, highlighting limitations in chiral symmetry breaking representation.

Findings

Masses and decay constants match experimental data.

Scalar mesons form linear Regge trajectories.

Couplings to pseudoscalar pairs are smaller than expected.

Abstract

We study light scalar mesons in the AdS/QCD soft-wall model with a background dilaton field. The masses and decay constants are compatible with experiment and QCD determinations if $a_0(980)$ and $f_0(980)$ are identified as the lightest scalar mesons; moreover, the states are organized in linear Regge trajectories with the same slope of vector mesons. Comparing the two-point correlation function of scalar operators in AdS and QCD, information about the condensates can be derived. Strong couplings of scalar states to pairs of light pseudoscalar mesons turn out to be small, at odds with experiment and QCD estimates: this discrepancy is related to the description of chiral symmetry breaking in this model.