Chiral and angular momentum content of mesons

TL;DR

This paper investigates the chiral and angular momentum structure of mesons, especially rho states, using a gauge-invariant method and lattice simulations, revealing differences between ground and excited states in symmetry and partial wave content.

Contribution

It introduces a gauge-invariant approach to measure meson chiral and angular momentum content at various scales, with lattice results showing novel insights into excited meson structures.

Findings

Chiral symmetry is strongly broken in rho(770)

The first excited rho(1450) has weaker chiral symmetry breaking

Infrared angular momentum content differs from quark model expectations

Abstract

First, we overview the present status of the effective chiral restoration in excited hadrons and an alternative explanation of the symmetry observed in the highly excited hadrons. Then we discuss a method how to define and measure in a gauge invariant manner the chiral and angular momentum content of mesons at different resolution scales, including the infrared scale, where mass is generated. We illustrate this method by presenting results on chiral and angular momentum content of rho and rho' mesons obtained in dynamical lattice simulations. The chiral symmetry is strongly broken in the rho(770) and neither the a_1(1260) nor the h_1(1170) can be considered as its chiral partners. Its angular momentum content in the infrared is approximately the 3S1 partial wave, in agreement with the quark model language. However, in its first excitation, rho(1450), the chiral symmetry breaking is much weaker and in the infrared this state belongs predominantly to the (1/2,1/2) chiral representation. This state is dominated in the infrared by the 3D1 partial wave and cannot be considered as the first radial excitation of the rho(770)-meson, in contrast to the quark model.