Observation of the $\ensuremath{\phi}(1680)$ and the $Y(2175)$ in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\phi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$

Rapid Communication

Observation of the $ϕ (1680)$ and the $Y (2175)$ in $e^{+} e^{-} \to ϕ π^{+} π^{-}$

C. P. Shen et al. (Belle Collaboration)

Phys. Rev. D 80, 031101(R) – Published 4 August 2009

Abstract

The cross sections for $e^{+} e^{-} \to ϕ π^{+} π^{-}$ and $e^{+} e^{-} \to ϕ f_{0} (980)$ are measured from threshold to $\sqrt{s} = 3.0 GeV$ using initial-state radiation. The analysis is based on a data sample of $673 {fb}^{- 1}$ collected on and below the $Υ (4 S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+} e^{-}$ collider. First measurements are reported for the resonance parameters of the $ϕ (1680)$ in the $ϕ π^{+} π^{-}$ mode: $m = (1689 \pm 7 \pm 10) MeV / c^{2}$ and $Γ = (211 \pm 14 \pm 19) MeV / c^{2}$ . A structure at $\sqrt{s} = 2.1 GeV / c^{2}$ , corresponding to the so called $Y (2175)$ , is observed; its mass and width are determined to be $(2079 \pm 13_{- 28}^{+ 79}) MeV / c^{2}$ and $(192 \pm 23_{- 61}^{+ 25}) MeV / c^{2}$ , respectively.