Revealing dipion correlations for the observed substructure near the $\pi^+\pi^-$ mass threshold in $\psi(3686)\to J/\psi\pi^+\pi^-$

TL;DR

This paper uses a chiral unitary approach to explain a dipion mass spectrum anomaly observed in $\psi(3686) o J/ e{psi}\pi^+\pi^-$ decays, revealing the role of dipion correlations in heavy quarkonium decay substructures.

Contribution

It introduces a novel application of a chiral unitary approach to reproduce and explain the dipion substructure anomaly in heavy quarkonium decay spectra.

Findings

Successfully reproduces the observed dipion mass anomaly

Provides evidence for dipion correlations in heavy quarkonium decays

Predicts the dipion correlation function in the decay process

Abstract

Based on the world's largest $\psi(3686)$ data sample, the BESIII Collaboration recently reported a substructure near the $\pi^+\pi^-$ mass threshold in the decay $\psi(3686) \to J/\psi \pi^+\pi^-$, challenging the established understanding of the dipion invariant mass spectrum. We propose that this substructure arises directly from dipion correlations. Using a chiral unitary approach, we successfully reproduce the observed anomaly, thereby providing strong evidence of dipion correlation in heavy quarkonium decays. This approach also allows us to predict the corresponding dipion correlation function.