Study of the pi+pi-J/psi Mass Spectrum via Initial-State Radiation at BABAR

Abstract

We present an update of the study of the Y(4260) resonance, produced in the process $e^{+}{e}^{-}\to {\gamma }_{ISR}{\pi }^{+}{\pi }^{-}J/\psi$ using initial-state radiation events at the PEP-II $e^{+}{e}^{-}$ storage rings. This study is based on 454fb${}^{-1}$ of data recorded with the {\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at a center-of-mass energy in the ${\rm Y}(4S)$ resonance region. From a fit with a single non-relativistic Breit-Wigner shape we obtain updated parameters for the Y(4260) resonance which are $m_Y=4252\pm 6_{-3}^{+2}$MeV/c${}^2$ and ${\Gamma }_Y=105\pm 18_{-6}^{+4}$MeV/c${}^2$; we also measure ${\calB}(π^+π^-J/ψ)Γ_{e^+e^-} = (7.5\pm 0.9 \pm0.8)$ eV. We cannot confirm the recent BELLE observation of a broad structure around 4.05GeV/c${}^2$ in this decay mode.

13 pages, 5 figures, contributed to ICHEP 2008