Effect of the $\eta\eta$ channel and interference phenomena in the two-pion transitions of charmonia and bottomonia

TL;DR

This paper explains the di-pion mass spectra in charmonia and bottomonia transitions through a unified mechanism involving coupled channels and interference effects, highlighting the role of $f_0$ resonances.

Contribution

It introduces a comprehensive model incorporating $\pi\pi$, $Kar{K}$, and $\eta\eta$ channels with interference to explain di-pion spectra in heavy quarkonium decays.

Findings

Unified explanation of di-pion spectra across charmonia and bottomonia.

Identification of the influence of $f_0$ resonances on mass distributions.

Demonstration of coupled-channel and interference effects in decay processes.

Abstract

The basic shape of di-pion mass spectra in the two-pion transitions of both charmonia and bottomonia states is explained by an unified mechanism based on contributions of the $\pi\pi$, $K\overline{K}$ and $\eta\eta$ coupled channels including their interference. The role of the individual $f_0$ resonances in shaping the di-pion mass distributions in the charmonia and bottomonia decays is considered.