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首页> 外文期刊>Physics letters >An improved limit for Γ e e of X ( 3872 ) and Γ e e measurement of ψ ( 3686 )
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An improved limit for Γ e e of X ( 3872 ) and Γ e e measurement of ψ ( 3686 )

机译: Γ e e / MathML“ altimg =” si2.gif“ display =” inline“ overflow =” scroll“> X 3872 Γ e e ψ 3686

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Using the data sets taken at center-of-mass energies above 4 GeV by the BESIII detector at the BEPCII storage ring, we search for the reaction e + e ? → γ ISR X ( 3872 ) → γ ISR π + π ? J / ψ via the Initial State Radiation technique. The production of a resonance with quantum numbers J PC = 1 + + such as the X ( 3872 ) via single photon e + e ? annihilation is forbidden, but is allowed by a next-to-leading order box diagram. We do not observe a significant signal of X ( 3872 ) , and therefore give an upper limit for the electronic width times the branching fraction Γ e e X ( 3872 ) B ( X ( 3872 ) → π + π ? J / ψ ) 0.13 ?eV at the 90% confidence level. This measurement improves upon existing limits by a factor of 46. Using the same final state, we also measure the electronic width of the ψ ( 3686 ) to be Γ e e ψ ( 3686 ) = 2213 ± 18 stat ± 99 sys ? eV .
机译:利用BEPCII存储环上的BESIII检测器在4 GeV以上的质心能量中心获取的数据集,我们搜索反应e + e? →γISR X(3872)→γISRπ+π?通过初始状态辐射技术获得J /ψ。通过单光子e + e?产生量子数为J PC = 1 + +的共振,如X(3872)。灭是被禁止的,但倒数第二个订单框图是允许的。我们没有观察到X的有效信号(3872),因此给出了电子宽度乘以分支分数Γee X(3872)B(X(3872)→π+π?J /ψ)<0.13的上限在90%的置信度水平上。此测量将现有限制提高了46倍。在相同的最终状态下,我们还将ψ(3686)的电子宽度测量为Γe eψ(3686)= 2213±18 stat±99 sys? eV。

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