Physics using ultra low-energy pulsed antiprotons

一种新的脉冲低能反质子源AD（antiproton decelerator）将于1999年在CERN投入运行。在AD，反质子氦原子的激光光谱学，我们在低能反质子环（LEAR）上开创的工作，将达到更高的精度。此外，还将研究其他奇异系统，如质子（一个反质子和一个质子的结合态）和反氢。主要研究结果如下：1.一项在CERN AD进行的实验提案，名为“使用慢反质子的原子光谱学和碰撞（ASACUSA）”，被提交给CERN，并获得批准。与CERN合作完成了射频四极反质子减速器的设计研究，该减速器可以将AD的5 MeV束流减速到约50 keV。对反质子氦激光光谱数据进行了详细的分析，并与近年来量子三体理论的高精度结果进行了比较。结果表明，该方法的测量精度优于2ppm，可以将反质子质量的测量精度从目前的50ppm提高到0.5ppm.进行了一个质子激光光谱学实验的概念设计。作为一个二体系统，不需要复杂的三体理论，就可以从质子能谱推导出反质子的质量。该计划将使用来自中微子的低能反质子，使用捕获阱进一步减速它们，并通过与原子氢碰撞在真空中形成质子。估计精度为10^<-9>或更好。

A new pulsed low-energy antiproton source, AD (antiproton decelerator), will start its operation from 1999 at CERN.This research, both experimental and theoretical, was conducted so as to develop research program using the AD beam. At AD, laser spectroscopy of antiprotonic helium atoms, the work we pioneered at the low energy antiproton ring (LEAR), will reach much higher precision. In addtion, study of other exotic systems such as protonium (bound state of an antiproton and a proton) and anti-hydrogen will be conducted. The major results are as follows :1. A proposal of an experiment at CERN AD, called "Atomic Spectroscopy and Collisions using Slow Antiprotons (ASACUSA)" was submitted to CERN, and was approved.2. The design study of-radio frequency quadrupole (RFQ) antiproton decelerator, which can decelerate the 5 MeV beam from the AD to about 50 keV, was completed in collaboration with CERN.3. Detailed analysis of antiprotonic helium laser spectroscopy data was done, and the results were compared with the high-precision results of recent quantum three-body theory. The agreement was better than 2 ppm, from which we could improve the accuracy of antiproton mass from the present value of 50 ppm to 0.5 ppm.4. A conceptual design of an experiment for protonium laser spectroscopy was done. Being a two-body system, it should be possible to deduce antiproton mass from protonium spectroscopy without the help of complicated three-body theories. The proposed scheme will use the low-energy antiprotons from the RFQ, decelerate them further using a catching trap, and form protoniums in vacuum by collision with atomic hydrogens. The estimated accuracy is 10^<-9> or better.