Study of the reaction e^{+}e^{-} -->J/psiπ^{+}π^{-} via initial-state radiation at BaBar

Abstract

We study the process $e^{+}{e}^{-}\to J/\psi {\pi }^{+}{\pi }^{-}$ 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 10.58 and 10.54 GeV, and correspond to an integrated luminosity of 454 $\mathrm{f}{\mathrm{b}}^{-1}$. We investigate the $J/\psi {\pi }^{+}{\pi }^{-}$ mass distribution in the region from 3.5 to 5.5 $GeV/{\mathrm{c}}^2$. Below 3.7 $GeV/{\mathrm{c}}^2$ the $\psi (2S)$ signal dominates, and above 4 $GeV/{\mathrm{c}}^2$ there is a significant peak due to the Y(4260). A fit to the data in the range 3.74 -- 5.50 $GeV/{\mathrm{c}}^2$ yields a mass value $4244\pm 5$ (stat) $\pm 4$ (syst)$MeV/{\mathrm{c}}^2$ and a width value $114_{-15}^{+16}$ (stat)$\pm 7$(syst)$\mathrm{MeV}$ for this state. We do not confirm the report from the Belle collaboration of a broad structure at 4.01 $GeV/{\mathrm{c}}^2$. In addition, we investigate the ${\pi }^{+}{\pi }^{-}$ system which results from Y(4260) decay.