The 3 flavor NJL with explicit symmetry breaking interactions: scalar and pseudoscalar spectra and decays

TL;DR

This paper extends the NJL model by including explicit symmetry breaking interactions to accurately describe scalar and pseudoscalar meson spectra and decays, aligning well with experimental data.

Contribution

It introduces NLO explicit symmetry breaking terms into the NJL model, improving the description of meson spectra and decay processes.

Findings

Accurately reproduces the mass splitting of meson nonets.

Explains scalar meson decays via multi-quark states.

Matches experimental data for pseudoscalar two-photon decays.

Abstract

The effective quark interactions that break explicitly the chiral SU(3)_L X SU(3)_R and U_A(1) symmetries by current-quark mass source terms are considered in NLO in $N_c$ counting. They are of the same order as the 't Hooft flavor determinant and the eight quark interactions that extend the LO Nambu-Jona-Lasinio Lagrangian, and complete the set of non-derivative and spin 0 interactions relevant for the $N_c$ scheme. The bosonized Lagrangian at meson tree level describes accurately the empirical ordering and magnitude of the splitting of states in the low lying pseudoscalar and scalar meson nonets, for which the explicit symmetry breaking terms turn out to be essential. The strong interaction and radiative decays of the scalar mesons are understood in terms of the underlying microscopic multi-quark states, which are probed differently by the strong and the electromagnetic interactions. We also obtain that the anomalous two photon decays of the pseudoscalars are in very good agreement with data.