使用0.37兆吨$\cdot$年曝光量的超级神冈的中子-反中子振荡搜索
Neutron-Antineutron Oscillation Search using a 0.37 Megaton$\cdot$Year Exposure of Super-Kamiokande
摘要：
中子-反中子振荡（$n\to\bar n$）作为一种与$ΔB=2$有关的重子数破坏过程，是检验重子数守恒的一种独特方法。利用前四个运行周期的完整数据集，我们对超级神冈中的束缚中子$n\to\bar n$振荡进行了搜索，其暴露量为0.37 Mton-年。该搜索使用了在模拟的$n\to\bar n$事件和大气中微子背景上训练的多变量分析，并产生了11个候选事件，预期背景为9.3个事件。在没有统计上显著过量的情况下，我们导出了$^{16}$ O核中$\bar n$出现寿命为$3.6\times{10}^{32}$年的下限和$τ_{n\to\bar n} > 4.7\times10^{8}$ ~s的中子-反中子振荡时间的下限。
英文摘要：
As a baryon number violating process with $ΔB=2$, neutron-antineutron oscillation ($n\to\bar n$) provides a unique test of baryon number conservation. We have performed a search for $n\to\bar n$ oscillation with bound neutrons in Super-Kamiokande, with the full data set from its first four run periods, representing an exposure of 0.37~Mton-years. The search used a multivariate analysis trained on simulated $n\to\bar n$ events and atmospheric neutrino backgrounds and resulted in 11 candidate events with an expected background of 9.3 events. In the absence of statistically significant excess, we derived a lower limit on $\bar n$ appearance lifetime in $^{16}$O nuclei of $3.6\times{10}^{32}$ years and on the neutron-antineutron oscillation time of $τ_{n\to\bar n} > 4.7\times10^{8}$~s at 90\% C.L..
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