寻找正电子湮没中费米黄金定则的修正项
Search for the correction term to the Fermi's golden rule in positron annihilation
摘要：
在正电子-电子湮灭过程中，最近的理论工作提出了有限的偏离基于费米黄金法则的标准计算。本文描述了一个实验测试的预测这一理论工作，通过搜索事件与两个光子的能量大于电子静止质量（$511\,{\rm keV}$）的正电子湮没。正电子来自${\rm {}^{22}Na}$源，标记来自${\rm {}^{22}{Ne}^*}$去激发的自发发射的第三个光子以抑制背景。利用收集到的$1.06\times 10^{7}$正电子-电子湮灭样品，研究了信号增强能区的三重符合光子事件。在两个信号区$N^{\rm SR1}_{\rm obs}=0$和$N^{\rm SR2}_{\rm obs}=0$中观察到的事件数在当前精度内分别与费米黄金法则的预期事件数$N^{\rm SR1}_{\rm exp}=0.86\pm0.08({\rm stat.})^{+1.85}_{-0.81}({\rm syst.})$和$N^{\rm SR2}_{\rm exp}=0.37\pm 0.05({\rm stat.})^{+0.80}_{-0.29}({\rm syst.})$一致。基于$P^{(d)}$模型，得到了光子波包大小的90% CL下限。
英文摘要：
In the positron-electron annihilation process, finite deviations from the standard calculation based on the Fermi's Golden rule are suggested in recent theoretical work. This paper describes an experimental test of the predictions of this theoretical work by searching for events with two photons from positron annihilation of energy larger than the electron rest mass ($511\,{\rm keV}$). The positrons came from a ${\rm {}^{22}Na}$ source, tagging the third photon from the spontaneous emission of ${\rm {}^{22}{Ne}^*}$ de-exitation to suppress backgrounds. Using the collected sample of $1.06\times 10^{7}$ positron-electron annihilations, triple coincidence photon events in the signal enhanced energy regions are examined. The observed number of events in two signal regions, $N^{\rm SR1}_{\rm obs}=0$ and $N^{\rm SR2}_{\rm obs}=0$ are, within a current precision, consistent with the expected number of events, $N^{\rm SR1}_{\rm exp}=0.86\pm0.08({\rm stat.})^{+1.85}_{-0.81}({\rm syst.})$ and $N^{\rm SR2}_{\rm exp}=0.37\pm 0.05({\rm stat.})^{+0.80}_{-0.29}({\rm syst.})$ from Fermi's golden rule respectively. Based on the $P^{(d)}$ modeling, the 90% CL lower limit on the photon wave packet size is obtained.
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