The S- and P-wave low-lying baryons in the chiral quark model

TL;DR

This paper investigates low-lying baryon states using the chiral quark model, incorporating various meson exchanges and a Gaussian expansion method, to address the mass order reverse problem and explore heavy baryon sectors.

Contribution

It introduces the scalar meson exchange potential into the chiral quark model and applies the Gaussian expansion method to study baryon states, including heavy quarks, providing insights into the mass order reverse problem.

Findings

Scalar meson exchange influences baryon mass ordering.

The model reproduces some experimental baryon masses.

The approach extends to heavy baryons with tentative state assignments.

Abstract

The $1S$, $2S$, $1P$ and $2P$ states of light baryons are investigated within the chiral quark model, paying particular attention to the well-known order reverse problem of $1P$ and $2S$ states. Besides a nonperturbative linear-screened confining interaction and a perturbative one-gluon exchange between quarks, we incorporate the Goldstone-boson exchanges taking into account not only the full octet of pseudoscalar mesons but also the scalar one. The scalar meson exchange potential simulates the higher order multi-pion exchange terms that appear in the chiral Lagrangian and its omission has been already admitted as a deficiency of the original model in describing, for instance, the $\rho-\omega$ splitting. The numerical approach to the three body bound state problem is the so-called Gau\ss ian expansion method, which is able to get a precision as good as Faddeev calculations. With a set of parameters fixed to different hadron and hadron-hadron observables, we find that the chiral potential could play an important role towards the issue on the mass order reverse problem. We extend our calculation to the $qqQ$ and $qQQ$ sectors (with $q$ representing a light $u$-, $d$-, or $s$-quark and $Q$ denoting the charm quark or the bottom one) in which many new states have been recently observed. Some tentative assignments are done attending to the agreement between theoretical and experimental masses; however, we admit that other sources of information are needed in order to make strong claims about the nature of these states.