Tetraquark Mesons in Large $N$ Quantum Chromodynamics

TL;DR

This paper explores the existence and properties of exotic tetraquark mesons in large N quantum chromodynamics, suggesting they are plausible and may explain certain observed mesons.

Contribution

It challenges the common belief that exotic mesons are ruled out in large N QCD, proposing two types of tetraquarks with distinct decay behaviors.

Findings

Short-lived tetraquarks have decay rates proportional to N.

Long-lived tetraquarks have decay rates proportional to 1/N.

Possible identification of $f_0(500)$ and $f_0(980)$ as tetraquarks.

Abstract

It is argued that exotic mesons consisting of two quarks and two antiquarks are not ruled out in quantum chromodynamics with a large number $N$ of colors, as generally thought. They can come in two varieties: short-lived tetraquarks with decay rates proportional to $N$, which would be unobservable if $N$ were sufficiently large, and long-lived tetraquarks with decay rates proportional to 1/N. The $f_0(500)$ and $f_0(980)$ may be examples of these two varieties of exotic mesons.