Y(4260) and Y(4360) as mixed hadrocharmonium

TL;DR

This paper proposes that the Y(4260) and Y(4360) resonances are mixed hadrocharmonium states with near-maximal mixing, explaining recent experimental data and predicting specific energy-dependent production patterns in electron-positron annihilation.

Contribution

It introduces a hadrocharmonium mixing model for Y(4260) and Y(4360), providing a new interpretation consistent with experimental observations and offering testable predictions.

Findings

Model aligns with BESIII data on $e^+e^- o h_c o ext{final states}$

Predicts distinctive interference patterns in energy dependence

Suggests near-maximal mixing of hadrocharmonium states

Abstract

Recent BESIII data indicate a significant rate of the process $e^+e^- \to h_c \pi^+ \pi^-$ at the Y(4260) and Y(4360) resonances, implying a substantial breaking of the heavy quark spin symmetry. We consider these resonances within the picture of hadrocharmonium, i.e. of (relatively) compact charmonium embedded in a light quark mesonic excitation. We suggest that the resonances Y(4260) and Y(4360) are a mixture, with mixing close to maximal, of two states of hadrochamonium, one containing a spin-triplet $c \bar c$ pair and the other containing a spin-singlet heavy quark pair. We argue that this model is in a reasonable agreement with the available data and produces distinctive and verifiable predictions for the energy dependence of the production rate in $e^+e^-$ annihilation of the final states $J/\psi \pi \pi$, $\psi' \pi \pi$ and $h_c \pi \pi$, including the pattern of interference between the two resonances.