Direct obsurvation of beauty particle decays and high statistic study of charm particles by the automatic measuring system with track selector

我们在高等实验基本粒子物理方面取得了突出的成果；美粒子衰变的直接观察与魅力粒子产生的研究。直接观察含有重夸克的美粲粒子是非常困难的，因为它们是在高能相互作用中极为罕见的产物，而且它们的寿命极短，约为0.1- 1ps。在本研究中，我们采用了一种由核乳化板堆和各种电子探测器组成的混合装置。由于乳剂具有非常高的空间分辨能力，因此在乳剂堆中可以充分观察到连接产生点和衰变点的美丽和魅力粒子的轨迹。为了高效地定位和分析核相互作用，我们采用了自己开发的独特的、功能强大的自动轨迹分析系统，其分析能力超过10000个事件/台/年。在CERN实验WA75.1中，在暴露于350 GeV <pi> <^->光束的乳剂靶中记录的3 x <10^8>相互作用中，我们发现了以下罕见事件：其中一个事件伴随着一对美丽粒子的产生，它们都在乳剂中衰变成迷人粒子。两种美丽粒子的加权平均飞行时间为0.3 +0.2/-0.1 ps，直接测量的寿命比其他实验中间接测量的寿命短。显然，迫切需要更多直接观察到的事件。2)两个事件，同时产生两对（四）迷人粒子在乳剂中衰变。双到单符咒副的实测率约为1/100。观测到的具有双重魅力对的事件的相当大的产生率与目前任何计算的结果都不一致。这激发了对重夸克强子化机制的更详细的QCD研究。名古屋大学在本研究过程中开发的全自动乳化液分析系统，极大地扩展了乳化液技术在基本粒子物理领域的应用。少

We have obtained outstanding results in the advanced experimental elementary particle physics; the direct observation of beauty particle decays and the study of charm particle production. The direct observation of the beauty and charm particles which contain heavy quarks in their constituents have been very difficult, because they are the extremely rare products in the high energy interactions, and because they have extremely short lifetimes of the order of 0.1-1 ps.In this study, we adopted a hybrid apparatus which consists of stacks of nuclear emulsion plates and the various electronic detectors. Because of a very high spatial resolvinig power inherent in the emulsion, tracks of beauty and charm particles connecting the production and decay points are fully observed in the emulsion stack. To locate and analyse nuclear interactions with high efficiency, we have utilized a unique and powerful automatic track analysing system developed by ourselves with analysing power higher than 10,00 … More 0 events/machine.year.We have discovered following rare events, out of 3 x <10^8> interactions recorded in the emulsion target exposed to the 350 GeV <pi> <^-> beam in the CERN experiment WA75.1) One event with the associated production of a pair of beauty particles both of which decayed into charm particles in the emulsion. The weighted mean flight time of the two beauty particles was measured to be 0.3 +0.2/-0.1 ps. This directly measured lifetime is shorter than that estimated by indirect method in the other experiments. Clearly, more events directly observed are urgently needed.2) Two events with the simultaneous production of two pairs (four) of charm particles decaying in the emulsion. The measured rate of double to single charm pair production is about 1/100. The rather large observed production rate of the events with double charm pairs is in disagreement with the results of any current calculations. This stimulates the more detailed QCD studies on the hadronization mechanism of the heavy quarks.The fully automated emulsion analysis system developed by the Nagoya University in the course of this study has greatly extended the adoptability of emulsion technique in the field of elementary particle physics. Less