Precision measurement of orthopositronium decay rate

束缚态QED的二阶修正是在2000年计算的。为了验证束缚态QED的计算和框架，我们对正电子偶素衰变率进行了精确测量。首先，我们开发了适合于高速率测量的新装置，以克服较大的统计误差。在装置中，我们采用了快速无机闪烁体雅普闪烁体。我们在以下条件下测量了两次正电子偶素衰变率。*运行I目标：SiO_2气凝胶数据采集周期：2.3个月 * RUN II目标：SiO_2粉末数据采集周期：3.1个月在两次测量中，我们改变了目标以测试材料对测量的影响。每次测量的数据量约为130 ppm的统计误差。所获得的拾取比，即零值与零值的比率， ...更多信息 对于实验I（SiO_2气凝胶）和实验II（SiO_2粉末），靶材中的SiO_2含量分别约为3%和1%。发现差异很大。我们认为这是由于SiO_2颗粒间的平均间距等精细结构的差异造成的，得到了各次的衰变率为：RUNI7.03876 ± 0.0009（stat.）0.0008-0.0010（系统）μs^<-1>* 运行II 7.04136+-0.0009（统计）+ 0.0007-0.0007（系统）μs^<-1>这些在1.6σ中彼此一致。合并结果为 * 运行I，II 7.0401+-0.0006（stat.）+ 0.0007-0.0009（系统）总<-1>误差约为150 ppm，是目前国际上最珍贵的，测量值与1995年以来的三次测量值一致，也与束缚态QED的O（α^2）计算值一致。另一方面，该值与O（α）计算相差约1.7σ。如果我们参考所测量的衰变率的世界平均值，差异达到2.6σ。因此，可以得出结论，测量的衰变率支持O（α^2）计算。少

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