Observation of Y(2175) in $J/ψ\to ηϕf_0(980)$
Abstract
Description
The decays of $J/ψ\to ηϕf_0(980) (η\to γγ, ϕ\to K^+K^-, f_0(980)\toπ^+π^-)$ are analyzed using a sample of $5.8 \times 10^{7}$ $J/ψ$ events collected with the BESII detector at the Beijing Electron-Positron Collider (BEPC). A structure at around $2.18 $GeV/$c^2$ with about $5σ$ significance is observed in the $ϕf_0(980)$ invariant mass spectrum. A fit with a Breit-Wigner function gives the peak mass and width of $m=2.186\pm 0.010 (stat)\pm 0.006 (syst) $GeV/$c^2$ and $Γ=0.065\pm 0.023 (stat)\pm 0.017 (syst) $GeV/$c^2$, respectively, that are consistent with those of Y(2175), observed by the BABAR collaboration in the initial-state radiation (ISR) process $e^+e^-\toγ_{ISR}ϕf_0(980)$. The production branching ratio is determined to be $Br(J/ψ\toηY(2175))\cdot Br(Y(2175)\toϕf_0(980))\cdot Br(f_0(980)\toπ^+π^-)=(3.23\pm 0.75 (stat)\pm0.73 (syst))\times 10^{-4}$, assuming that the Y(2175) is a $1^{--}$ state.
5 pages, 4 figures, accepted by Phys. Rev. Lett
5 pages, 4 figures, accepted by Phys. Rev. Lett