Exotic pentaquarks as Gamov-Teller resonances

TL;DR

This paper models baryon resonances using a mean-field approach at large Nc, predicting exotic pentaquarks as Gamov-Teller resonances and suggesting potential stable charmed pentaquarks for experimental search.

Contribution

It introduces a mean-field model for baryons at large Nc that explains known resonances and predicts new stable charmed pentaquarks, extending nuclear physics concepts.

Findings

Baryon spectra align with experimental data at Nc=3

Light pentaquark Theta+ is a Gamov-Teller resonance

Predicted stable charmed pentaquarks Beta++_c and Beta+_c

Abstract

If the number of colors Nc is taken large, baryons and their excitations can be considered in a mean-field approach. We argue that the mean field in baryons breaks spontaneously the spherical and SU(3) flavor symmetries, but retains the SU(2) symmetry of simultaneous rotations in space and isospace. The one-quark and quark-hole excitations in the mean field, together with the SU(3) rotational bands about them determine the spectrum of baryon resonances, which turns out to be in satisfactory accordance with reality when one puts Nc=3. A by-product of this scheme is a confirmation of the light pentaquark baryon Theta+ = uudds-bar as a typical Gamov-Teller resonance long known in nuclear physics. An extension of the same large-Nc logic to charmed (and bottom) baryons leads to a prediction of a anti-decapenta (15-bar)-plet of charmed pentaquarks, two of which, Beta++_c = cuuds-bar and Beta+_c = cudds-bar, may be light and stable with respect to strong decays, and should be looked for.