Glueball Interpretation of ξ(2230)

On the basis of the results of ξ(2230) → π+π−, pp̄ and KK̄, measured by the BES Collaboration in radiative J/ψ decays, combined with the upper limit of Br(ξ → pp̄)Br(ξ → KK̄), measured by PS185 experiment, we argue that the distinctive properties of ξ(2230), the flavor-symmetric decays and the narrow partial decay widths to ππ andKK̄ as well as its copious production in radiative J/ψ decay, would strongly favor the glueball interpretation of ξ(2230). PACS number(s): 14.40.Cs, 12.38.Aw, 11.30.Hv, 13.20.Gd BES Collaboration have reported their new results about ξ(2230) [1]. They confirmed the existence of ξ(2230) in the decays J/ψ → γKK̄ and they also found two new non-strange decay modes ξ → pp̄ and π+π−. The preliminary results of the mass, width and branching ratios of ξ(2230) measured by BES are the following[1]: In J/ψ → γπ+π− process, Mξ = (2235 − 4 − 6)MeV, Γξ = (19 +13+ −11−12)MeV, Br(J/ψ → γξ) Br(ξ → π +π−) = (5.6 −1.6−1.4) × 10 −5. In J/ψ → γK+K− process, Mξ = (2230 +6+ −7−12)MeV, Γξ = (20 +20+ −15−12)MeV, Br(J/ψ → γξ) Br(ξ → K+K−) = (3.3 −1.3−1.1) × 10 −5. In J/ψ → γpp̄ process, Mξ = (2235 + − 4 − 5)MeV, Γξ = (15 −9− 9)MeV, Br(J/ψ → γξ)Br(ξ → pp̄) = (1.5 +0.6+ −0.5−0.5)× 10 −5. Previous theoretical interpretations of ξ(2230) included identification as a high spin ss̄ state[2], a multiquark state (such as a 4-quark state[3,4], a ΛΛ̄ bound state[5], a neutral color scalar bound state [6], etc.), a hybrid state[3,7] and a glueball[8]. Since Mark III Collaboration only found strange decay modes of ξ(2230)[9], the ss̄ interpretation seemed plausible and the glueball interpretation would be ruled out. The new discovery of BES experiments on nonstrange decay modes provides us with extremly important clue so that the nature of ξ(2230) will become clear. Compared with other mesons, ξ(2230) has many distinctive properties: (1) flavor-symmtric decays. With the phase space factors removed, it can be found that the probability of ξ → π+π−