Exotic $$J^{PC}=1^{-+}$$ J P C = 1 - + mesons in a holographic model of QCD

L Bellantuono,P Colangelo,F Giannuzzi

doi:10.1140/epjc/s10052-014-2830-6

Abstract

Mesons with quantum numbers $J^{PC}=1^{-+}$ cannot be represented as simple quark-antiquark pairs. We explore hybrid configurations in the light meson sector comprising a quark, an antiquark and an excited gluon, studying the properties of such states in a phenomenological model inspired by the gauge/gravity correspondence. The computed mass, compared to the experimental mass of the $1^{-+}$ candidates $\pi_1(1400)$, $\pi_1(1600)$ and $\pi_1(2015)$, favous $\pi_1(1400)$ as the lightest hybrid state. An interesting result concerns the stability of hybrid mesons at finite temperature: they disappear from the spectral function (i.e. they melt) at a lower temperature with respect to other states, light vector and scalar mesons, and scalar glueballs.

Highlights

There are combinations of spin, parity and charge conjugation of meson quantum numbers that cannot be obtained by a quark model description of a quark–antiquark pair with orbital angular momentum L and quark spin Sq and Sq
We explore hybrid configurations in the light meson sector comprising a quark, an antiquark and an excited gluon, studying the properties of such states in a phenomenological model inspired by the gauge/gravity correspondence
An interesting result concerns the stability of hybrid mesons at finite temperature: they disappear from the spectral function at a lower temperature with respect to other states, light vector and scalar mesons and scalar glueballs

Summary

Introduction

There are combinations of spin, parity and charge conjugation of meson quantum numbers that cannot be obtained by a quark model description of a quark–antiquark pair with orbital angular momentum L and quark spin Sq and Sq. If new hadronic states can be obtained explicitly considering the dynamics of gluonic excitations, hybrid configurations with non-exotic quantum numbers should be present in the meson spectrum. Their identification in this case is more difficult, due to the mixing with the ordinary qqconfigurations, and one has to mainly look for overpopulation of the levels with respect to, e.g., the quark model predictions. One can fix c including the mass of the excited states of the 1−− spectrum, or the whole Regge trajectory, as done in [40] In the latter case, we obtain c ∼ 474 MeV and M0 ∼ 1.34 GeV. The expression for the residues is obtained, which are interesting to compare with the outcome of different approaches

Thermal effects on the hybrid meson spectrum

Conclusions