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Test of QCD from measurement of the lifetime ofπィイD1+ィエD1πィイD1-ィエD1 atoms using a fast topological trigger system

使用快速拓扑触发系统测量 πD1+D1πD1-D1 原子的寿命来测试 QCD

基本信息

批准号：
09440112
负责人：
KOBAYASHI Masaaki
金额：
$ 4.48万
依托单位：
High Energy Accelerator Research Organization
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

Test of the quantum chromodynamics (QCD) is important in order to discover and phenomena beyond the standard model of elementary particle physics. Although QCD is known to hold pretty well at high energies, test of QCD at low energies is not easy since calculation has to be carried out without using perturbative method due to the large coupling constant in Lagrangian. We have planned an experiment, called DIRAC, of measuring the decay lifetime of πィイD1+ィエD1πィイD1-ィエD1 atoms to πィイD10ィエD1πィイD10ィエD1 at CERN PS to test the predictions of CHPT, the effective theory of QCD at low energies, to an accuracy of 5%, and started data-taking in 1999. In this experiment, it is important to detect precisely two minimum-ionising particles at short distances (<5-6 mm) within 100 ns after the occurrence of the event. We developed necessary fast Scifi and dE/dx detectors for position and dE/dx measurements, respectively. While we detect πィイD1+ィエD1πィイD1-ィエD1 pairs coming from dissociation of πィイD1+ィエD1πィイD1-ィエD1 atoms in DIRAC, direct detection of decay πィイD10ィエD1πィイD10ィエD1 should have a merit for improved experiment in future. So, we also carried out R&D for fast, heavy and radiation-hard scintillators for excellent g-ray detectors.1. Scifi-detectors and fast triggering electronics were successfully constructed and are now in use.2. We have succeeded in developing (1) Si-detectors (64x64mmィイD12ィエD1 in size, 300μm thick and read-out at a step of 1-2mm), (2) charge preamplifier with decay time of 100-240 ns and ENC of 3000e, and (3) shaping amplifier of gain 50 and pulse width of 50 ns. This will replace the present dE/dx detectors of plastic-scintillato strips from 2001.We have made significant improvement in heavy, fas and radiation hard scintillators such as PbWOィイD24ィエD2, GdィイD22ィエD2SiOィイD25ィエD2:Ce, etc.

为了发现超出基本粒子物理标准模型的现象，对量子色动力学(QCD)进行测试是非常重要的。虽然QCD在高能下保持得很好，但在低能下QCD的测试并不容易，因为拉格朗日耦合常数很大，计算不需要使用微扰方法。我们计划了一项名为DIRAC的实验，在欧洲核子研究中心PS上测量πィイD_1+ィエD_1πィイD_1-ィエD_1原子到πィイD_10ィエD_1πィイD_10ィエD_1的衰变寿命，以检验CHPT的预测，即低能QCD的有效理论，精度为5%，并于1999年开始数据采集。在这个实验中，重要的是在事件发生后的100 ns内，在短距离(&lt；5-6 mm)内准确地探测到两个最小电离粒子。我们开发了必要的快速SCRIFI和De/DX探测器，分别用于位置和De/Dx测量。虽然我们检测到的πィイd1+ィエd1πィイd1-ィエd1对来自πィイd1+ィエd1πィイd1-ィエd1原子的解离，但直接检测衰变的πィイd10ィエd1πィイd10ィエd1应该是一种改进实验的优点。因此，我们还开展了用于优秀g-射线探测器的快、重和耐辐射闪烁体的研发工作。科学探测器和快速触发电子设备已成功建造并投入使用。我们成功地研制了(1)硅探测器(尺寸为64×64 mmィイD12ィエD_1，厚度为300μm，读出步长为1-2 mm)，(2)电荷前置放大器，衰变时间为100-240 ns，ENC为3000E，(3)整形放大器，增益为50 ns，脉宽为50 ns。这将从2001年起取代目前塑料闪烁带的De/DX探测器。我们在重闪烁体、FAS和耐辐射闪烁体方面取得了重大改进，如PbWOィイD24ィエD2，GdィイD22ィエD2SiOィイD25ィエD2：Ce等。