b decays: a factory for hidden charm multiquark states

TL;DR

This paper models hidden charm pentaquark states as multiquark systems with specific color and angular momentum configurations, predicting their masses, decay channels, and experimental signatures, especially in beauty decays.

Contribution

It introduces a detailed theoretical framework for understanding hidden charm multiquark states, including mass predictions and decay mechanisms, based on constituent quark models and chromomagnetic interactions.

Findings

Predicted masses of pentaquark states at 4360, 4410, 4490, and 4560 MeV.

Identified key open channels like $p J/\psi$ and $\Lambda_c \bar{D}^{0*}$.

Explained the small width of the $\frac{5}{2}^+$ state due to gluon exchange requirements.

Abstract

We assume that the two hidden charm pentaquark discovered at $LHCb$ are built by the three light quarks and the $c \bar{c}$ pair, both colour octets. in relative P-wave for the $\frac{5}{2}^+$ state and by the eigenvectors of the chromomagnetic interaction for the five constituents in S-wave for the four $\frac{3}{2}^-$ state with masses $4360$, $4410$, $4490$ and $4560$ MeV . The "open channel" $p $ $J/\psi$ has large components along the two first states and so appear as the $4380$ resonance and the $\Lambda_c$ $ \bar{D}^{0*}$ and $\Sigma_c$ $\bar{D}^*$ are "open channels" for the lower and higher resonances, respectively. The expectation for their strange isoscalar partners is to have a mass larger by an amount of the order or smaller than the $M_{\Lambda} - M_N$ mass difference. We account for the small width of the $\frac{5}{2}^+$, since its decay needs the exchangeof a gluon and stress that the decays of particles with "beauty" provide the best experimental framework for the discovery of hidden charm multiquarks. The relevance of the production mechanics shows the reason why only some of the states with non minimal number of constituents have been found.