Precision measurement of orthopositronium decay rate

精确测量正正电子素衰变率

• 批准号: 17540236
• 负责人: KOBAYASHI Tomio
• 金额: $ 2.24万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2005
• 资助国家: 日本
• 起止时间: 2005 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17540236/
• 关键词: Elementary particle physics; Positronium; QED; higher order correction

The second order correction of the bound state QED had been calculated in 2000. To test the calculation and the framework of the bound state QED, we have performed the precision measurement of the Orthopositronium decay rate. First of all, we have developed the new setup suitable for the high rate measurement in order to overcome the large statistic error. In the setup, we have adapted the YAP scintillator, which is the fast inorganic scintillator.We have measured the Orthopositronium decay rate two times in the following conditions.* RUN I target : SiO_2 aerogel data taking period: 2.3 months* RUN II target : SiO_2 powder data taking period: 3.1 monthsIn two measurements, we have changed the target to test the influence of the material on the measurement. The amount of data taken in each measurement corresponds to about 130ppm of the statistic error.We have adapted the direct pick-off correction method in the measurement. The obtained pick-off ratio, which is the ratio of the annihila … More tion in the target material, is about 3% for RUN I (SiO_2 aerogel) and about 1% for RUN II (SiO_2 powder). The difference is found to be large. And it is considered to be come from the difference of the fine structure of the material such as the mean distance between the SiO_2 grains.The obtained decay rates for each run are* RUN I 7.03876+-0.0009 (stat.)+0.0008-0.0010 (sys.) μs^<-1>* RUN II 7.04136+-0.0009 (stat.)+0.0007-0.0007 (sys.) μs^<-1>These are consistent with each other in 1.6σ.The combined result is* RUN I, II 7.0401+-0.0006 (stat.)+0.0007-0.0009 (sys.) μs^<-1>The total error is about 150ppm and the most precious in the world.The measured value is consistent with the three measurements from 1995 and also agreed with the O( α^2) calculation by the bound state QED. On the other hand, the value differs from the O(α) calculation by about 1.7σ. If we refer to the world average of the measured decay rate, the discrepancy reaches 2.6σ. Therefore, one can conclude the measured decay rate supports the O(α^2) calculation. Less

在2000年计算了结合状态QED的二阶校正。为了测试结合状态QED的计算和框架，我们进行了正邻化衰减率的精确测量。首先，我们开发了适合高利率测量的新设置，以克服较大的统计误差。在设置中，我们对YAP闪烁器进行了改编，这是快速无机的闪烁体。在以下条件下，我们测量了两次正交衰减速率。每个测量中采集的数据量对应于统计误差的约130ppm。我们改编了测量中的直接拾取校正方法。所获得的拾取比率（即目标材料中的更多比率）对于运行I（SIO_2气凝胶）约为3％，Run II（SIO_2粉末）约为1％。发现差异很大。它被认为来自材料的良好结构的差异，例如SIO_2粒之间的平均距离。每次运行的衰减率是*运行* 7.03876+-0.0009（stat。 μs^<-1>它们在1.6σ中彼此一致。组合结果是*运行I，II 7.0401+-0.0006（stat。）+0.0007-0.0009（sys。）μs^<-1>总误差约为150ppm，在世界上最珍贵。与测量值最宝贵。州QED。另一方面，该值与O（α）计算的不同大约1.7σ。如果我们指的是测得的衰减率的世界平均值，则差异达到2.6σ。因此，可以包括测得的衰减速率支持O（α^2）计算。较少的