# Chromopolarizability of charmonium and $\pi\pi$ final state interaction revisited

## TL;DR

This paper revisits the chromopolarizability of charmonium by analyzing heavy quarkonium decays with a dispersion theory approach that accounts for $\pi\pi$ final state interactions, providing more accurate measurements.

## Contribution

It introduces a model-independent dispersion theory analysis of $\pi\pi$ FSI effects on charmonium chromopolarizability extraction, refining previous estimates.

## Key findings

- The $\pi\pi$ FSI significantly reduces the chromopolarizability estimate.
- The chromopolarizability is determined as $|\alpha_{\psi^\prime ext{ extbackslash}psi}|=1.44 ext{ GeV}^{-3}$.
- The parameter $\kappa$ is measured as $0.139$ with small uncertainty.

## Abstract

The chromopolarizability of a quarknonium describes the quarknonium's interaction with soft gluonic fields and can be measured in the heavy quarkonium decays. Within the framework of dispersion theory which consider the $\pi\pi$ final state interaction (FSI) model-independently, we analyze the transition $\psi^\prime\to J/\psi\pi^+\pi^-$ and obtain the chromopolarizability $\alpha_{\psi^\prime \psi}$ and the parameter $\kappa$. It is found that the $\pi\pi$ FSI plays an important role in extracting the chromopolarizability from the experimental data. The obtained chromopolarizability with the FSI is reduced to about 1/2 of that without the FSI. With the FSI, we determine the chromopolarizability $|\alpha_{\psi^\prime\psi}|=(1.44\pm 0.02)$ GeV$^{-3}$ and the parameter $\kappa=0.139\pm 0.005.$ Our results could be useful in studying the interactions of charmonium with light hadrons.