Experimental Study of the H-particle

H粒子的实验研究

• 批准号: 01044132
• 负责人: TAKEUTCHI Fujio
• 金额: $ 6.46万
• 依托单位: Kyoto Sangyo University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for international Scientific Research
• 财政年份: 1989
• 资助国家: 日本
• 起止时间: 1989 至 1991
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-01044132/
• 关键词: H-particle; Hypernucleus; Strangeness; Color magnetic interaction; XI stop events; AGS; Aerogel cerenkov counter; Quark degree of freedom; 〓^ーストップ事象; アエロジェル・チェレンコフ・カウンタ-; フォ-ク自由度; ダイバリオン; K^-ビ-ム; カウンタ-実験; TOFカウンタ-; チェレンコフカウンタ-

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

Jaffe在1977年预言的H粒子是一个非常独特的天体。组成两个波长的粒子被认为只有通过彩色磁相互作用才能强烈结合。因此，它的存在与原子核中的夸克自由度密切相关。该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，我们的目标都是识别H粒子并确定其质量。在E813中，K^束被引向液氢靶，产生的XI粒子被阻止在邻近的液氢靶中。测量了Xid-GT；hn反应产生的反冲中子的动量。在E836中，改为使用液体^3He靶。然而，由于美国的资金问题，使得AGS加速器的运行时间大大缩短，因此在该项目结束之前，只能运行一次E813。我们开始了探测器的设计和e…的测试在KEK进行更多的实验。BNL的新光束线的建造工作已于1990年夏天完成。此外，光谱仪磁铁也在大约同一时间安装。建造和测试了暗室、AcroGel Cerenkov计数器和Time-of-fliglight Counicr。可疑的低温靶也工作得很好。KEK的E176实验告诉我们，被K^-击中的靶上有相当丰富的反冲质子。因此，还增加了一台Lucitc Cerenkov计数器，但在1991年4月实验开始后，分束器上的高压无法达到设计值750kV。我们必须在600千伏的电压下进行实验，这迫使我们必须以1.7GeV/c的束流动量运行。这次事故使结果的统计数据减少到预期事件数量的6%左右。1991年7月运行后，立即开始数据分析。到1991年11月，确认所有探测器工作正常，并发现了XI停止事件。以便于辨认。这一结果是由P.D.BAMEs在1991年12月在岛田举行的超核物理国际研讨会上报告的。数据整理目前正在进行中。但考虑到1991年的数据缺乏统计数据，而且政府账目委员会已批准延长E813的使用期限，而且从1992年5月开始另一次为期8周的测试，我们决定推迟公布结果，直到新的数据加入现有的数据。这一次我们可以预期运行在1.8GeV/c。从这一点，以及触发系统的改进，我们预计这次将发生大约170R氢事件，其中R是从XID原子产生氢的分支比率。基于上述原因，尚未准备好出版，但我们预计这将在1992年发生。较少