Study of the reaction e^{+}e^{-}->psi(2S)pi^{-}pi^{-} via initial state radiation at BaBar

Abstract

We study the process $e^+e^-\toψ(2S)π^{+}π^{-}$ 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 $Υ(\mathrm{nS})$ (n = 2, 3, 4) resonances and correspond to an integrated luminosity of 520$fb^{-}$. We investigate the $ψ(2S)π^{+}π^{-}$ mass distribution from 3.95 to 5.95 $GeV/c^{2}$, and measure the center-of-mass energy dependence of the associated $e^+e^-\to ψ(2S)π^{+}π^{-}$ 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 $ψ(2S)\to J/ψπ^{+}π^{-}$ yields a mass value of $4340 \pm16$ (stat) $\pm 9$ (syst) ${\mathrm {MeV/c^{2}}}and a width of $94 \pm 32$ (stat) $\pm 13$ (syst) MeV for the first resonance, and for the second a mass value of $4669 \pm 21$ (stat) $\pm 3$ (syst) ${\mathrm {MeV/c^{2}}}$ and a width of $104 \pm 48$ (stat) $\pm 10$ (syst) MeV. In addition, we show the $pi^{+}π^{-}$ mass distributions for these resonant regions.