Experimental Study of the H-particle

1977年由Jaffe预言的H粒子是一个非常独特的物体。组成两个λ粒子被认为是强烈的约束，只有通过色磁相互作用。本项目的目标是在布鲁克海文国家实验室新建的大强度K束线上进行两个实验：E813和E836。在这两个实验中，我们的目标是识别H粒子并确定其质量。在E813中，K^-束被引导到液氢靶，并且所产生的Xi粒子在相邻的液体氘靶中停止。测量了来自XId->Hn反应的反冲中子的动量。在E836中，使用了液态^3He靶。但由于美国的经费问题，加速器运行时间大大缩短，E813只能运行一次，因此在项目结束前，我们开始了探测器的设计和测试工作，并进行了初步的研究。 ...更多信息 在KEK的实验。BNL新光束线的建设于1990年夏天完成。此外，光谱仪磁铁安装在大约同一时间。实验室、acrogel cerenkov计数器、飞行时间计数器都已建成并进行了测试。双低温靶也工作得很好。KEK的E176实验告诉我们，被K^-击中的靶中有大量反冲质子。但1991年4月实验启动后，束流分离器上的高压达不到750 kV的设计值。我们必须在600 kV下运行实验，这迫使我们在1.7 GeV/c的束流动量下运行。这次事故使统计结果减少到预期事件数的6%左右。1991年7月运行后，立即开始了数据分析。到1991年11月，所有的探测器都按预期运行，并且发现Xi停止事件是可识别的。该结果由P. D. Bames在1991年12月下田举行的超核物理国际讨论会上作了介绍。但由于1991年的数据缺乏统计数据，PAC批准了E813的延期，1992年5月又开始了8周的运行，我们决定推迟公布结果，直到新的数据加入到现有的数据中。我们可以预期这次运行在1.8 GeV/c。由此，再加上触发系统的改进，我们预计这次将发生大约170个RH事件，其中R是XId原子产生H的分支比。由于上述原因，尚未准备好出版，但我们预计将在1992年期间出版。少

The H-particle, predicted by Jaffe in 1977, is a quite unique object. The constituent two lambda particles are thought to be strongly bound only through color magnetic interactions. Therefore its existence is strongly related with the quark degree of freedom in nuclei.The objective of this project was to carry out two experiments ; E813 and E836 at the newly-constructed large-intensity K-beam line at Brookhaven National Laboratory. In both experiments we aim at identifying the H-particle and determining its mass. In E813, the K^- beam is lead to the liquid hydrogen target, and the produced XI particle is stopped in the neighboring liquid deuterium target. The momentum of the recoil neutron from the XId->Hn reaction is measured. In E836, a liquid ^3He target is used instead. However the funding problem in US drastically reduced the running time of AGS accelerator, thus only one run of E813 could take place, before the end of this project.We started the design of the detectors and test e … More xperiments at KEK. The construction of the new beam line at BNL was completed in summer 1990. Also the spectrometer magnet was installed at about the same time. The chambers, the acrogel cerenkov counters, the timc-of-fliglit counicr were built and tested. The doubic cryogenic target worked well too. The experiment E176 at KEK taught us that recoil protons are quite abundant from the target hit by K^-. So a newly added lucitc cerenkov counter was also installed.However after the start up of the experiment in April 1991, the high voltage on the beam separators could not reach the designed value of 750 kV. We had to run the experiment at 600 kV, and this obliged us to run at 1.7 GeV/c beam momentum. This accident reduced the statistics of the result to about 6% of the expected number of events.Immediately after the run in July 1991, the data analysis started. By November 1991, it was confirmed that all the detectors performed as expected, and the XI stop events are found. to be identifiable. This result was reported by P. D. Bames at the international symposium on the hypernuclear physics held in Shimoda in December 1991.The data reduction is now in progress. But from that fact that the 1991 data lack the statistics, and an extension of E813 is approved at the PAC, and another run of 8 weeks starts in may 1992, we've decided to postpone the publication of the results until the new data are added to the existing ones.The conditioning of the separators is now in progress. We can expect to run at 1.8 GeV/c this time. From this, and from the improvements in the trigger system, we expect to take about 170R H events this time, where R is the branching ratio of H production from the XId atom.For the reason stated above, a publication is not yet ready, but we expect that to happen in the course of 1992. Less