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A double pulse separator for a lifetime measurement of pionic atoms.

用于测量介子原子寿命的双脉冲分离器。

基本信息

批准号：
09640376
负责人：
OKADA Kenji
金额：
$ 1.34万
依托单位：
Kyoto San-gyo University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

A validity of QCD has not been proved yet at low energy region, where the interaction between quarks is too strong to be treated as a perturbation. The aim of this research is to test the QCD at an unperturbed low energy by measuring a life time of pionic atoms A_<2pi>(bound state of pi+pi-) with 10% accuracy. (DIRAC CERN-PS212) The life time of A_<2pi> is related to the scattering length of pi-pi scattering in S-state and is preciesly predicted by a Chiral perturbation theory. To extract real rare A_<2pi> events from huge amount of background events experimentally, we have to develop a new type trigger device providing some topological information in the real time. The topological trigger device employed here consists of scintillating fiber hodoscopes (SCIFI) followed by position sensitive photo-multipliers (PSPM) and double constant fraction discriminators(DCFD) for a delay-line read-out device giving distances among multiple hit particles.Analog signals from multi-anodes of the PSPM were read by means of delay line method to reduceelectronic modules and were converted to timing signals by the double side CFDs. Performances of them were tested by using high energy secondary particles produced by 24GeV protons. The double pulse separation was found to be good for the double pulses with an interval larger than 1.5 nsec, which corresponds to 1.5mm distance beteen the two particles on the hodoscope, The two particle identification efficiency, position resolution and time resolution were measured and were satisfactorily good. We found that the hodoscope with 5 layers of 0.5mm SCIFI was a little bit thin to give a stable pulse shape for the DSCFD and didn't give a well separation at the distance less than 1.5mm.We found that when the DCFD devices are used for dinode output together with anode signals, such infomation as a time difference and a position distance between two particles needed for trigger devices can be obtained in real time.

QCD在低能区的有效性尚未被证明，因为在低能区，夸克之间的相互作用太强，不能被视为微扰。这项研究的目的是通过测量光子原子的寿命A_&lt；2pi&gt；(pi+pi-的束缚态)，以10%的准确度在不受扰动的低能量下测试QCD。(Dirac CERN-PS212)A&lt；2pi&gt；的寿命与S态的pi-pi散射的散射长度有关，并用手征微扰理论精确地预测了它的寿命。为了从大量的背景事件中从实验中提取真实的稀有事件，我们必须开发一种新型的实时提供一些拓扑信息的触发装置。本文采用的拓扑触发装置由闪烁光纤显微镜(SCRIFI)、位置灵敏光电倍增器(PSPM)和双恒分数鉴别器(DCFD)组成，用于延迟线读出装置，给出多个命中粒子之间的距离。通过延迟线方法读取PSPM多个阳极的模拟信号，以简化电子模块，并通过双边CFD转换为定时信号。利用24GeV质子产生的高能次级粒子对它们的性能进行了测试。对于间隔大于1.5毫微秒的双脉冲，即示波器上两粒子之间的距离为1.5 mm的双脉冲，采用双脉冲分离的方法，测量了两粒子的识别效率、位置分辨率和时间分辨率，获得了令人满意的结果。我们发现，采用5层0.5 mm的SCFI的示波器较薄，不能提供稳定的DSCFD脉冲形状，并且在小于1.5 mm的距离下不能很好地分离。我们发现，当DCFD器件与阳极信号一起用于二极管输出时，可以实时获得触发器件所需的时间差和两个粒子之间的位置距离等信息。