The excited baryon spectrum from a unified quark model

Abstract

A common approach to studying the multiquark states is to solve the few-body Schr\"odinger equation within a quark potential model. The multiquark states may contain quarks with several different flavors and have richer color structures than ordinary hadrons. The reliability of such an investigation requires that the underlying quark potential model can simultaneously describe the meson and baryon spectra across all flavor sectors, including orbital and radial excitations, with a single parameter set. At present, no quark potential model fully satisfies this requirement. We construct a simple nonrelativistic constituent quark potential model that includes spin--orbit and tensor interactions. We refit the model parameters to the latest experimental data. The excited light hadrons and several exotic hadron candidates are excluded from the fit. The resulting parameter set reproduces the spectra across all fitted sectors. The vast majority of deviations are below 20 MeV, while the largest deviations remain of the order of several tens of MeV, which is the typical accuracy of nonrelativistic quark potential models. Using the same parameters, we predict the spectra and internal structures of the orbitally and radially excited heavy baryons, which await further experimental determination. The excited light baryons are calculated with the same parameters. The calculated excited light baryon spectra deviate substantially from experimental values. Our refitted model does not resolve these longstanding discrepancies. The results delimit the range of validity of the nonrelativistic constituent quark potential model. By treating mesons and baryons across all flavor sectors, including both orbital and radial excitations within a unified framework, the model provides a controlled starting point for few-body calculations of multiquark states. We also urge experimental searches for the predicted states.