Study of the reaction e+e- →ψ (2S)π+π- via initial-state radiation at B a B ar

Abstract

We study the process e+e-→ψ(2S)π+π- with initial-state-radiation events produced at the PEP-II asymmetric-energy collider. The data were recorded with the BABAR detector at center-of-mass energies at and near the (nS) (n=2,3,4) resonances and correspond to an integrated luminosity of 520fb-1. We investigate the ψ(2S)π+π- mass distribution from 3.95 to 5.95GeV/c2, and measure the center-of-mass energy dependence of the associated e+e-→ψ(2S)π+π- cross section. The mass distribution exhibits evidence of two resonant structures. A fit to the ψ(2S)π+π- mass distribution corresponding to the decay mode ψ(2S)→J/ψπ+π- yields a mass value of 4340±16(stat) ±9(syst)MeV/c2 and a width of 94±32(stat)±13(syst)MeV for the first resonance, and for the second a mass value of 4669±21(stat) ±3(syst)MeV/c2 and a width of 104±48(stat)±10(syst)MeV. In addition, we show the π+π- mass distributions for these resonant regions. © 2014 American Physical Society.