在 J-PARC KOTO 实验中寻找 K_{L}→π^{0}νν[over ¯] 和 K_{L}→π^{0}X^{0} 衰变。
Search for K_{L}→π^{0}νν[over ¯] and K_{L}→π^{0}X^{0} Decays at the J-PARC KOTO Experiment.
机构信息
Department of Physics, Korea University, Seoul 02841, Republic of Korea.
Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.
出版信息
Phys Rev Lett. 2019 Jan 18;122(2):021802. doi: 10.1103/PhysRevLett.122.021802.
A search for the rare decay K_{L}→π^{0}νν[over ¯] was performed. With the data collected in 2015, corresponding to 2.2×10^{19} protons on target, a single event sensitivity of (1.30±0.01_{stat}±0.14_{syst})×10^{-9} was achieved and no candidate events were observed. We set an upper limit of 3.0×10^{-9} for the branching fraction of K_{L}→π^{0}νν[over ¯] at the 90% confidence level (C.L.), which improved the previous limit by almost an order of magnitude. An upper limit for K_{L}→π^{0}X^{0} was also set as 2.4×10^{-9} at the 90% C.L., where X^{0} is an invisible boson with a mass of 135 MeV/c^{2}.
进行了一项对罕见衰变 K_{L}→π^{0}νν[over ¯] 的搜索。利用 2015 年采集的对应于 2.2×10^{19} 个质子靶的数据分析，实现了单个事例灵敏度为 (1.30±0.01_{stat}±0.14_{syst})×10^{-9}，没有观察到候选事例。我们在 90%置信水平（C.L.）下对 K_{L}→π^{0}νν[over ¯]的分支比设定了一个 3.0×10^{-9}的上界，这比之前的结果提高了近一个数量级。我们还在 90%置信水平下对 K_{L}→π^{0}X^{0}设定了一个 2.4×10^{-9}的上界，其中 X^{0}是一个质量为 135 MeV/c^{2}的不可见玻色子。
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