Effective chiral restoration in the rho'-meson in lattice QCD

TL;DR

This study investigates the chiral structure of the excited rho-meson in lattice QCD, revealing that its wave function differs from the ground state and shows signs of effective chiral restoration at different scales.

Contribution

First lattice QCD study to analyze the chiral mixing in the excited rho-meson using the variational method with dynamical quarks.

Findings

The excited rho-meson couples predominantly to the (1/2,1/2)_b representation.

The rho' contains a significant 3D1 wave component, deviating from quark model predictions.

Infrared chiral partner of rho' is likely h_1(1380).

Abstract

In simulations with dynamical quarks it has been established that the ground state rho in the infrared is a strong mixture of the two chiral representations (0,1)+(1,0) and (1/2,1/2)_b. Its angular momentum content is approximately the 3S1 partial wave which is consistent with the quark model. Effective chiral restoration in an excited rho-meson would require that in the infrared this meson couples predominantly to one of the two representations. The variational method allows one to study the mixing of interpolators with different chiral transformation properties in the non-perturbatively determined excited state at different resolution scales. We present results for the first excited state of the rho-meson using simulations with n_f=2 dynamical quarks. We point out, that in the infrared a leading contribution to rho'= rho(1450) comes from (1/2,1/2)_b, in contrast to the rho. Its approximate chiral partner would be a h_1(1380) state. The rho' wave function contains a significant contribution of the 3D1 wave which is not consistent with the quark model prediction.