Tetraquark Properties at Large $N_{\rm c}$

TL;DR

This paper analyzes the properties of exotic tetraquark mesons with four distinct quark flavors in the large $N_c$ limit of QCD, suggesting multiple such states with different decay modes, challenging simple diquark models.

Contribution

It provides a theoretical framework for understanding the existence and decay properties of multiple exotic tetraquarks in the large $N_c$ limit of QCD.

Findings

Multiple tetraquarks with the same quark content can exist at large $N_c$.

Different tetraquarks can be distinguished by their decay modes.

The results challenge the diquark-antidiquark bound state model.

Abstract

Considering quantum chromodynamics in the consistent limit of simultaneous correlated increase of the number of colours, $N_{\rm c}$, beyond bounds and decrease of the strong coupling to zero allows for solid statements about qualitative features of the class of "truly exotic" tetraquark mesons carrying four mutually distinct quark flavours. Consistency criteria extracted from correlation functions for two-ordinary-meson scattering suggest the existence of more than one such tetraquarks, at least, of two tetraquarks of identical quark-flavour content and large-$N_{\rm c}$ behaviour of the total decay widths but differing in, and hence discriminable by, their predominant decay modes into two conventional mesons. This pairwise appearance is in conflict with the unique variant of such a four-quark bound state arising from the binding of diquark and antidiquark to a tetraquark by the strong interactions.