Observation ofY(2175)inJ/ψ→ηϕf0(980

Abstract

The decays of J/psi --> etaphif(0)(980)[eta --> gammagamma, phi --> K(+) K(-), f(0)(980) --> pi(+)pi(-)] are analyzed using a sample of 5.8 x 10(7) J/psi events collected with the BESII detector at the Beijing Electron-Positron Collider. A structure at around 2.18 GeV/c(2) with about 5 sigma significance is observed in the phif(0)(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/c(2) and Gamma = 0.065+/-0.023(stat)+/-0.017(syst) GeV/c(2), respectively, which are consistent with those of Y(2175), observed by the BABAR Collaboration in the initial-state radiation process e(+)e(-) --> gamma(ISR) phif(0)(980). The production branching ratio is determined to be Br(J/psi --> etaY(2175))Br(Y(2175)- -> phif(0)(980))Br(f(0)(980) --> pi(+)pi(-)) = [3.23+/-0.75(stat)+/-0.73(syst)] x 10(-4), assuming that the Y(2175) is a 1(--) state.

Meson-exchange model for theΛΛ¯interaction

“…Later, the BES Collaboration also observed a similar structure in the decay of J=c ! f 0 ð980Þ with about 5 significance [2]. Since both Yð2175Þ and Yð4260Þ are produced in e þ e À annihilation and exhibit similar decay patterns, Yð2175Þ might be interpreted as an s" s analogue of the Yð4260Þ or as an s" ss " s state that decays predominantly to ð1020Þf 0 ð980Þ [1].…”

Possible partner state of the Y(2175)

“…The Yð2175Þ was first observed in 2006 by the BABAR Collaboration in the ϕf 0 ð980Þ invariant mass spectrum [14][15][16][17], and later confirmed in the BESII [18], Belle [19], and BESIII [20,21] experiments. Its mass and width were measured to be M ¼ 2188 AE 10 MeV and Γ ¼ 83 AE 12 MeV, respectively, and its spin-parity quantum number is J PC ¼ 1 −− [1].…”

“…The BABAR [14,15], Belle [19], BESII [18], and BESIII [20] experiments observing the Yð2175Þ as well as the fit performed in Ref. [22].…”

“…(e) The ϕf 0 ð980Þ invariant mass spectrum. Taken from BESII [18]. (f) The ϕf 0 ð980Þ invariant mass spectrum.…”

Nonstrange partner of strangeonium-like stateY(2175)

“…ð1020Þf 0 ð980Þ [1], which was later confirmed by BESII in J=c ! ð1020Þf 0 ð980Þ [2] and by Belle in the e þ e À ! ð1020Þf 0 ð980Þ, ð1020Þ þ À processes [3].…”