Gluon string breaking and meson spectrum in the holographic Soft Wall model

TL;DR

This paper introduces a holographic Soft Wall model for QCD that predicts meson spectra by analyzing gluon string breaking, naturally incorporating chiral symmetry breaking and parity splitting, with results aligning well with experimental data.

Contribution

It presents a novel bottom-up holographic model that automatically incorporates chiral symmetry breaking and predicts meson spectra using a new string breaking condition.

Findings

Accurate predictions for meson Regge trajectories.

Natural mass splitting between parity partners.

Agreement with experimental and phenomenological data.

Abstract

We propose a general method for finding a string-like meson spectrum which is based on a certain condition for the breaking of closed gluon string. A model is constructed that successfully realizes the proposed method. The model is based on the holographic Soft Wall model for QCD and the use of the Wilson confinement criterion. We applied our approach to the vector and scalar cases and obtained numerical predictions for the intercepts of corresponding Regge like radial meson spectra. A good agreement is obtained both with the existing experimental data and with some other known phenomenological approaches. Remarkably, our closed string breaking condition has two branches. We argue that they should correspond to states of opposite parity. The Wilson confinement criterion leads then to a natural mass splitting between parity partners. The constructed model represents thus the first example of bottom-up holographic model in which the effects of chiral symmetry breaking can emerge automatically, i.e., without additional assumptions taken outside of the holographic approach.