Extra charmonium states as bag-quarkonia

TL;DR

This paper models exotic charmonium states as bag-quarkonia, incorporating nonperturbative effects and bag contributions to explain observed spectra, decay widths, and anomalies in low invariant mass regions.

Contribution

It introduces a novel framework combining a Coulomb-like potential with bag excitation effects to describe exotic charmonium states and their decay properties.

Findings

Agreement with experimental data on low invariant mass pion distributions.

Improved description of leptonic decay widths of vector states.

Identification of the bag contribution as a constant at low distances.

Abstract

Exotic states in the charmonium family are systematically treated in the framework of simplest model with an effective coulomb-like interaction of heavy quark and antiquark in the presence of static excitation of quark-gluon modes responsible for a nonperturbative term of potential, which provides with the confinement of quarks, in terms of bag over the threshold in the excitation spectrum of vacuum fields. Once the spectrum has got quite a wide mass gap, it allows us to approximate the bag contribution into the potential by a constant value of bag mass at low distances less than the bag size. The bag mass can be evaluated in a constituent model. The analysis is given for the bag contribution into the distribution over the invariant mass of two pions in the hadronic transition between the S-wave states of bag-quarkonium and heavy quarkonium, that leads to the anomaly violating the chiral limit in the region of low invariant masses, which agrees with the observational data. Leptonic constants of vector states are investigated in the presence of exotic states in the framework of quasilocal sum rules. The extra states allow us to improve the consistency of describing the measured widths of leptonic decays for the complete set of vector states in the charmonium family.