尋找B介子衰變至不可見末態粒子

Abstract

在本論文中我們尋找B介子至不可見末態衰變。此次實驗的測量結果是根據由Belle 偵測器所收集到約六億五千七百萬個B與反B介子事件而得到。由沒有明顯信號，我們給予90%信心水準的衰變機率(B)上限：B(B→invisible)<1.3×10-4

We report a new search for B decays into invisible final states using a data sample of 657 million BB pairs collected at Y(4S) resonance with the Belle detector at the KEKB e+e- collider. The nu nu signals are identified by fully reconstructing the accompanying $B$ mesons and requiring no other charged particles and no extra energy deposited in the calorimeter. By performing maximum likelihood fits to the reconstructed candidates, no significant signal is observed and we set the upper limit on the branching fraction B(B→invisible)<1.3×10-4 at the 90% confidence level.