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为了实验研究粲偶素ψ'级联衰变过程ψ'→γ'xcJ→γ'γJ/ψ,一个用于正确描述全部末态角分布的产生子是必要的.可以通过分析角分布的关联来确定这一过程的多极展开参数(或者等效的螺旋度振幅),而从中可以知道高阶电磁多极矩和相对论修正的贡献,同时可以检验ψ'是不是ψ'(2S)和ψ'(1D)的混合.介绍了一个能完全描述这一过程的角分布的产生子,同时讨论了测量多极参数的测量方法.这些都可以被用在BESⅢ或者CLEOc的分析当中. 相似文献
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The BEPCⅡ Luminosity Monitor (BLM) monitors relative luminosity per bunch. The counting rates of gamma photons, which are proportional to the luminosities from the BLM at the center of mass system energy of the ψ(3770) resonance, are obtained with a statistical error of 0.01% and a systematic error of 4.1%. Absolute luminosities are also determined by the BESⅢ End-cap Electro-Magnetic Calorimeter (EEMC) using Bhabha events with a statistical error of 2.3% and a systematic error of 3.5%. The calibration constant between the luminosities obtained with the EEMC and the counting rates of the BLM are found to be 0.84±0.03 (×1026 cm-2·count-1). With the calibration constant, the counting rates of the BLM can be scaled up to absolute luminosities. 相似文献
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