Mesons as Open Strings in a Holographic Dual of QCD

TL;DR

This paper models meson spectra using open string modes in a holographic QCD framework, deriving a mass formula that aligns with observed meson properties and includes higher-spin states.

Contribution

It introduces a holographic dual model of QCD with massive open string modes to describe meson spectra, including higher-spin mesons, with a derived mass formula exhibiting Regge behavior.

Findings

Mass formula exhibits linear Regge trajectories.

Identifies specific mesons as excited open string states.

Captures features of observed meson spectrum.

Abstract

We study meson spectrum obtained from massive open string modes in a holographic dual of QCD constructed on the basis of a D4/D8-brane configuration in type IIA string theory. The spectrum includes mesons with spin higher than one. Taking into account the effect of curved background perturbatively, we obtain a mass formula for these mesons, which exhibits the linear Regge behavior at the leading order with subleading non-linear corrections. We argue that the string spectrum captures some features of the observed meson spectrum. For example, a_2(1320), b_1(1235), \pi(1300), a_0(1450), etc., are identified as the first excited massive open string states and \rho_3(1690), \pi_2(1670), etc., are identified as the second excited states.