Low-lying even parity meson resonances and spin-flavor symmetry revisited

TL;DR

This paper revisits a spin-flavor extended chiral model to better describe low-lying even parity meson resonances, improving agreement with experimental data across multiple meson sectors by refining symmetry-breaking contact terms.

Contribution

It introduces a comprehensive analysis of SU(6) symmetry breaking contact terms in a coupled channels model, enhancing the description of J^P=2^+ meson resonances without disrupting previous predictions.

Findings

Improved description of f_2(1270), a_2(1320), and K*_2(1430) resonances.

Enhanced model accuracy for J^P=2^+ sector.

Maintained consistency with earlier results in J^P=0^+ and J^P=1^+ sectors.

Abstract

We review and extend the model derived in Phys. Rev. D83 016007 (2011) to address the dynamics of the low-lying even parity meson resonances. This model is based on a coupled channels spin-flavor extension of the chiral Weinberg-Tomozawa Lagrangian. This interaction is then used to study the S-wave meson-meson scattering involving members not only of the \pi-octet, but also of the \rho-nonet. In this work, we study in detail the structure of the SU(6) symmetry breaking contact terms that respect (or softly break) chiral symmetry. We derive the most general local (without involving derivatives) terms consistent with the chiral symmetry breaking pattern of QCD. After introducing sensible simplifications to reduce the large number of possible operators, we carry out a phenomenological discussion of the effects of these terms. We show how the inclusion of these pieces leads to an improvement of the description of J^P = 2^+ sector, without spoiling the main features of the predictions obtained in the original model in the J^P = 0^+ and J^P = 1^+ sectors. In particular, we find a significantly better description of the I^G(J^{PC})=0^+(2^{++}), 1^-(2^{++}) and the I(J^{P})=\frac{1}{2}(2^{+}) sectors, which correspond to the f_2(1270), a_2(1320) and K^*_2(1430) quantum numbers, respectively.