Abstract
The state Y(2175) is observed in the process e+e-→ηY(2175) with a statistical significance larger than 10 standard deviations using the data collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies between 3.7 and 4.6 GeV. This is the first observation of the Y(2175) in this process. The mass and width of the Y(2175) are determined to be (2135±8±9) MeV/c2 and (104±24±12) MeV, respectively, and the production cross section (σ) of e+e-→ηY(2175)→ηϕf0(980)→ηϕπ+π- is at the several hundred femtobarn level. No significant signal for the process e+e-→η′Y(2175) is observed and the upper limit on σ(e+e-→η′Y(2175))/σ(e+e-→ηY(2175)) is estimated to be 0.43 at the 90% confidence level. We also search for ψ(3686)→ηY(2175). No significant signal is observed, indicating a strong suppression relative to the corresponding J/ψ decay, in violation of the “12% rule”.
Highlights
The Yð2175Þ, which is notated as φð2170Þ in Ref. [1], was first observed in 2006 by the BABAR Collaboration [2] via the initial-state-radiation (ISR) process eþe− → γISRφf0ð980Þ with a mass of ð2175 Æ 10 Æ 15Þ MeV=c2 and a decay width of ð58 Æ 16 Æ 20Þ MeV
We present the first observation of eþe− → ηYð2175Þ and measurement of its production cross sections, a search for eþe− → η0Yð2175Þ and an estimation of the upper limit of the production rate at the c.m. energies [21] from 3.686 to 4.6 GeV, and a search for ψð3686Þ → ηYð2175Þ and determination of the upper limit on the branching fraction, as listed in Table I with the corresponding integrated luminosities L [22]
The process eþe− → η0Yð2175Þ is simulated at each energy point with a similar procedure, and the decay η0 → γπþπ− is generated as η0 → γρ0 with ρ0 → πþπ− [33]
Summary
The Yð2175Þ, which is notated as φð2170Þ in Ref. [1], was first observed in 2006 by the BABAR Collaboration [2] via the initial-state-radiation (ISR) process eþe− → γISRφf0ð980Þ with a mass of ð2175 Æ 10 Æ 15Þ MeV=c2 and a decay width of ð58 Æ 16 Æ 20Þ MeV. [1], was first observed in 2006 by the BABAR Collaboration [2] via the initial-state-radiation (ISR) process eþe− → γISRφf0ð980Þ with a mass of ð2175 Æ 10 Æ 15Þ MeV=c2 and a decay width of ð58 Æ 16 Æ 20Þ MeV. [20] predict the existence of a sharp peaking structure (Zs1) close to the KK Ã threshold and a broad structure (Zs2) close to the KÃK Ã threshold in the φπ mass spectrum These can be searched for using the decays of the Yð2175Þ produced in eþe− → ηYð2175Þ and η0Yð2175Þ.
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