Unquenched quark-model calculation of excited $\rho$ resonances and P-wave $\pi\pi$ phase shifts

TL;DR

This study uses an unquenched quark model with multiple decay channels to analyze the $ ho$ resonances and P-wave $\pi ext{ extpi}$ phase shifts, successfully reproducing key features at low energies.

Contribution

It introduces a comprehensive unquenched quark model including 26 decay channels to study $ ho$ resonances and phase shifts, extending previous models.

Findings

Model reproduces $ ho$ mass and width

Successfully fits low-energy phase shifts

Phase shifts rise too sharply at higher energies

Abstract

The $\rho(770)$ vector resonance, its radial recurrences, and the corresponding P-wave $\pi\pi$ phase shifts are investigated in an unquenched quark model with all classes of relevant decay channels included, viz. pseudoscalar-pseudoscalar, vector-pseudoscalar, vector-vector, vector-scalar, axialvector-pseudoscalar, and axialvector-vector, totalling 26 channels. Two of the few model parameters are fixed at previously used values, whereas the other three are adjusted to the $\rho(770)$ resonance and the lower P-wave $\pi\pi$ phases. Preliminary results indicate the model's capacity to reproduce these phases as well as the $\rho$ mass and width. However, at higher energies the phase shifts tend to rise too sharply. A possible remedy is an extension of the model so as to handle resonances in the final states for most of the included decay channels. Work in progress.