Possible mixing of a diquark-antidiquark with a $p \bar p$ hadronic molecule

TL;DR

This paper explores the potential mixing between a proton-antiproton hadronic molecule and a diquark-antidiquark bound state, explaining the observed near-threshold resonances with a novel internal structure hypothesis.

Contribution

It introduces the idea that two nearby resonances could result from mixing between different internal configurations with identical quantum numbers.

Findings

Resonances may be due to mixing of different internal states.

One resonance could be a hadronic molecule, the other a diquark-antidiquark bound state.

The phenomenon might be a general feature in hadronic physics.

Abstract

We discuss the possibility that the two nearby resonances observed by BESIII partially below the \,$p\bar p$\, threshold might be due to mixing between two metastable states with the same $J^{PC}=0^{-+}$ quantum numbers, but rather different internal structure. One is a $p \bar p$ hadronic molecule and the other a bound state of a light-quark diquark and an antidiquark, both with spin 1 and isospin 0, a composite color antitriplet and triplet, respectively. The doubling of resonances, one of which may be interpreted as a hadronic molecule, while the other arises from $q \bar q$ annihilation in a state with vacuum quantum numbers may be a more general feature than the specific case considered here.