2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/166837We present an update of the study of the Y(4260) resonance, produced in the process $e^+e^-\toγ_{ISR} π^+π^-J/ψ$ 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 $Υ(4S)$ resonance region. From a fit with a single non-relativistic Breit-Wigner shape we obtain updated parameters for the Y(4260) resonance which are $m_Y = 4252 \pm6 ^{+2}_{-3}$MeV/c$^2$ and $Γ_Y = 105 \pm 18^{+4}_{-6}$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 2008High Energy Physics - Experimenttext