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年预测到的h粒子是一个非常独特的物体。组成两个λ粒子被认为只有通过色磁相互作用才能强结合。因此，它的存在与原子核中的夸克自由度密切相关。这个项目的目标是进行两个实验；在布鲁克海文国家实验室新建的大强度k束线上的E813和E836。在这两个实验中，我们的目标是确定h粒子并确定它的质量。在E813中，K^-束被引导到液氢靶，产生的XI粒子被停在邻近的液氘靶中。测量了XId-> - Hn反应的反冲中子的动量。在E836中，使用了液体^3He靶。然而，美国的资金问题大大缩短了AGS加速器的运行时间，因此在该项目结束之前，E813只能运行一次。我们开始了探测器的设计和测试…更多的实验在KEK。在1990年夏天，在BNL建造了新的梁线。同时也安装了磁谱仪。舱室、凝胶切伦科夫计数器、飞行时间委员会都被建造和测试了。双低温靶也表现良好。KEK的E176实验告诉我们，被K^-撞击的目标产生的反冲质子相当丰富。因此，还安装了一个新增加的lucitc切伦科夫计数器。但1991年4月试验启动后，束流分离器上的高压达不到750 kV的设计值。我们必须在600千伏的电压下进行实验，这迫使我们以1.7 GeV/c的光束动量运行。这次事故使统计结果减少到预期事件数的6%左右。在1991年7月的运行之后，立即开始了数据分析。到1991年11月，证实所有探测器都按预期运行，并且发现了11个停止事件。可识别。这一结果由p.d. Bames在1991年12月下田举行的超核物理国际研讨会上报告。数据缩减工作正在进行中。但是从1991年的数据缺乏统计数据这一事实来看，E813的延期在PAC上被批准，另一个8周的运行开始于1992年5月，我们决定推迟结果的公布，直到新数据添加到现有数据中。分离器的调节工作正在进行中。这次我们可以期望以1.8 GeV/c运行。根据这一点，以及对触发系统的改进，我们预计这次会发生大约170R H事件，其中R是XId原子产生H的分支比。由于上述原因，出版物尚未准备好，但我们期望在1992年期间完成。少