Heavy baryon spectrum with chiral multiplets of scalar and vector diquarks

TL;DR

This paper develops a chiral effective theory for scalar and vector diquarks to model the spectra of singly heavy baryons, using a potential quark model and lattice QCD data to predict positive and negative parity states.

Contribution

It introduces a novel heavy-quark--diquark model based on chiral effective theory and applies it to predict heavy baryon spectra, incorporating lattice QCD data and experimental comparisons.

Findings

Negative parity states of $\Xi_Q$ differ from $\Lambda_Q$ due to pseudoscalar diquark hierarchy.

Similar spectra observed for $\Sigma_Q$, $\Xi'_Q$, and $\Omega_Q$ baryons.

Model results agree with experimental data and quark model predictions.

Abstract

Chiral effective theory of scalar and vector diquarks is formulated according to the linear sigma model. The main application is to describe the ground and excited states of singly heavy baryons with a charm or bottom quark. Applying the potential quark model between the diquark and the heavy quark ($Q=c, b$), we construct a heavy-quark--diquark model. The spectra of the positive- and negative-parity states of $\Lambda_Q$, $\Sigma_Q$, $\Xi^{(')}_Q$ and $\Omega_Q$ are obtained. The masses and interaction parameters of the effective theory are fixed partly from the lattice QCD data and also from fitting low-lying heavy baryon masses. We find that the negative parity excited states of $\Xi_Q$ (flavor $\bar{\bf 3}$) are different from those of $\Lambda_Q$, because of the inverse hierarchy of the pseudoscalar diquark. On the other hand, $\Sigma_Q, \Xi'_Q$ and $\Omega_Q$ (flavor ${\bf 6}$) baryons have similar spectra. We compare our results of the heavy-quark--diquark model with experimental data as well as the quark model.