Multiquark study of exotic open bottom baryonic states

Abstract

We present a simultaneous study of baryon-meson systems containing a bottom degree of freedom, either as a quark or as an antiquark. This produces two different types of structures: the NB system, subject to quark antisymmetry effects and whose existence would generate explicit exotic states; and the NB¯ system, subject to the coupling to heavy baryon–light meson systems and whose existence would represent a higher Fock space component of the bottom baryon spectrum. Both systems have been studied within the framework of a full-fledged chiral constituent quark model tuned in the description of the baryon and meson spectra and the NN interaction. Although the masses of the constituents are larger than its partners in the charm sector, we do not observe a proliferation of bound states. This is due to the coupled-channel mechanism that governs the dynamics for most spin-isospin channels, and requires, in order to have a bound state, several conditions that are difficult to be met at the same time. Our results point to the existence of a deep NB bound state in the (T)JP=(2)3/2- channel, as a consequence of the reduction of the mass difference between pseudoscalar and vector mesons when the mass of the heavy quark increases. The same effect gives rise to a resonance at threshold in the (T)JP=(0)1/2- channel, the best candidate for an exotic state among the channels that do not contain a Δ isobar. In the NB¯ system, a few channels may lodge molecular or compact hadrons with a five-quark structure, being specially suited the (T)JP=(0)1/2- and (T)JP=(1)5/2- channels.