Search for proton Decay p*nuK^+

用5万吨水切伦科夫探测器“Super-Kamiokande”探测到了质子衰变模p*NUK^+。具体是通过寻找氧衰变产生的伽马射线和介子的延迟符合信号来实现的。我们首先制作了一个光发射器，模拟了从伽玛射线和介子产生的切伦科夫光，考虑了它们的能量和角度。然后将光发射体放入Super-Kamiokande探测器中，研究了伽马射线和Muon的探测效率。结果发现，在延迟时间为5ns的情况下，该算法的效率非常高，足以满足当前的搜索要求。结果如下：我们没有发现质子衰变的证据，因此设定了质子寿命的下限除以分支比(tau/B)；从介子能谱--2.8*10^&lt；32&gt；年，从介子衰变pi^++pi^0-1.3*10^&lt；32&gt；年，从目前的分析伽马+Mu-1.5*10^&lt；32&gt；年，这些结果是世界上对质子衰变p*nUK最强的极限。目前的方法最终将提供最敏感的限制，因为搜索是不受背景影响的。

A proton decay mode p*nuK^+ has been searched for with a 50,000ton water Cherenkov detector "Super-Kamiokande". A search was carried out specifically by looking for a delayd coincidence signal of a gamma ray and a muon which are produced from an Oxygen decay^<16>O* ^<15>N^<**>+K^++nu, ^<15>N^<**>* ^<15>N+gamma, K^+*mu^++nu.We first made a light emitter which simulates Cherenkov light from the gamma ray and muon taking into account of their energies and angles. The light emitter was then lowered into the Super-Kamiokande detector and the detection efficiency of the gamma ray and muon was studied. It was found that the efficiency was excellent up to 5nsec of delay time, which is sufficient for the present search.We then analyzed the 414 day-data obtained by Super-Kamiokande. The results are the following : We have not found evidence for the proton decay and therefore set the lower limit of proton lifetime divided by the branching ratio (tau/B) ;From the muon energy-spectrum------2.8*10^<32> years,From the Kaon decay pi^++pi^0-----1.3*10^<32> years,From the present analysis gamma+mu---1.5*10^<32> years,These results are the strongest limit on the proton decay p*nuK in the world. The present method will eventually provide the most sensitive limit, since the search is free from background.