# Charged charmoniumlike structures in the $e^+ e^- \to \psi(3686) \pi^+ \pi^-$ process based on the ISPE mechanism

## TL;DR

This paper demonstrates that the initial single pion emission (ISPE) mechanism can accurately reproduce the charged charmonium-like structure observed in the $e^+ e^- o \psi(3686) \\pi^+ \\pi^-$ process, providing a plausible explanation for this phenomenon.

## Contribution

It offers the first detailed analysis showing the ISPE mechanism can explain the charged charmonium-like structure in this process.

## Key findings

- The charged structure can be reproduced by the ISPE mechanism.
- The dipion invariant mass spectrum matches experimental data.
- The cross section is consistent with observations.

## Abstract

In 2017, the BESIII Collaboration announced the observation of a charged charmonium-like structure in the $\psi(3686)\pi^\pm$ invariant mass spectrum of the $e^+ e^- \to \psi(3686) \pi^+ \pi^-$ process at different energy points, which enables us to perform a precise study of this process based on the initial single pion emission (ISPE) mechanism. In this work, we perform a combined fit to the experimental data of the cross section of $e^+ e^- \to \psi(3686) \pi^+ \pi^-$, and the corresponding $\psi(3686)\pi^\pm$ and dipion invariant mass spectra. Our result shows that the observed charged charmonium-like structure in $e^+ e^- \to \psi(3686) \pi^+ \pi^-$ can be well reproduced based on the ISPE mechanism, and that the corresponding dipion invariant mass spectrum and cross section can be depicted with the same parameters. In fact, it provides strong evidence that the ISPE mechanism can be an underlying mechanism resulting in such novel a phenomenon.