Evidence of a Broad Structure at an Invariant Mass of 4.32 GeV/$c^2$ in the Reaction $e^+e^-\to\pi^+\pi^-\psi(2S)$ Measured at BaBar

TL;DR

This paper reports the observation of a broad resonance structure near 4.32 GeV in the cross section of the process e+e- to pi+ pi- psi(2S), using initial-state radiation data from BaBar, suggesting possible new exotic states.

Contribution

First measurement of the e+e- to pi+ pi- psi(2S) cross section up to 8 GeV revealing a new structure near 4.32 GeV, and analysis of its relation to the Y(4260).

Findings

Observation of a broad structure at 4.32 GeV in the cross section.

The structure is not far above the threshold and may be related to exotic states.

Compatibility with the Y(4260) is investigated.

Abstract

We present a measurement of the cross section of the process $e^+e^-\to\pi^+pi^-\psi(2S)$ from threshold up to 8 GeV center-of-mass energy using events containing initial-state radiation, produced at the PEP-II $e^+e^-$ storage rings. The study is based on 298 fb$^{-1}$ of data recorded with the BaBar detector. A structure is observed in the cross-section not far above threshold, near 4.32 GeV. We also investigate the compatibility of this structure with the Y(4260) previously reported by this experiment.