Observation of Two Resonant Structures in e+e- to pi+ pi- psi(2S) via Initial State Radiation at Belle

TL;DR

This study measures the e+e- to pi+ pi- psi(2S) cross section using Belle data, revealing two new resonant structures that do not correspond to known charmonium states.

Contribution

First observation of two new resonant structures in e+e- to pi+ pi- psi(2S) via initial state radiation at Belle, expanding understanding of charmonium-like states.

Findings

Two resonant structures observed at 4361 MeV/c2 and 4664 MeV/c2

Resonances do not match known charmonium states

Widths of the resonances are 74 MeV and 48 MeV

Abstract

The cross section for e+e- to pi+ pi- psi(2S) between threshold and \sqrt{s}=5.5 GeV is measured using 673 fb^{-1} of data on and off the \Upsilon(4S) resonance collected with the Belle detector at KEKB. Two resonant structures are observed in the pi+ pi- psi(2S) invariant mass distribution, one at 4361\pm 9\pm 9 MeV/c2 with a width of 74\pm 15\pm 10 MeV/c2, and another at 4664\pm 11\pm 5 MeV/c2 with a width of 48\pm 15\pm 3 MeV/c2, if the mass spectrum is parameterized with the coherent sum of two Breit-Wigner functions. These values do not match those of any of the known charmonium states.