Observation of Y(2175) in J/ψ&rarr f0(980)

摘要

The decays of J/ψ&rarrη f0(980)[η&rarrγγ, &rarrK+K-,f0(980)&rarrπ+π-] are analyzed using a sample of 5.8×107 J/ψ events collected with the BESII detector at the Beijing Electron-Positron Collider. A structure at around 2.18GeV/c2 with about 5σ significance is observed in the f0(980) invariant mass spectrum. A fit with a Breit-Wigner function gives the peak mass and width of m=2.186±0. 010(stat)±0.006(syst)GeV/c2 and Γ=0.065±0.023(stat) ±0.017(syst)GeV/c2, respectively, which are consistent with those of Y(2175), observed by the BABAR Collaboration in the initial-state radiation process e+e-&rarrγISR f0(980). The production branching ratio is determined to be Br(J/ψ&rarrηY(2175))Br(Y(2175)&rarr f0(980))Br(f0(980)&rarrπ+π-)=[3.23±0.75(stat)±0.73(syst)] ×10-4, assuming that the Y(2175) is a 1 - state.

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