KOPIO (BNL-E926) is an experiment which is concerned with CP violation and which is due in 2005 at BrookhavenNational Laboratory. The aim is to measure the branching ratio of K0L->pi0nu~nu(K zero Long meson decays and generates a pi zero meson and neutrino-antineutrino pair) which is ~10-11 order.
The method for identifying K0L-> pi0nu~nu decay mode is by detecting 2gammas from pi0 ->2gamma and not to veto events which contain gammas from another pi0 or other charged particles. So, it is necessary to get rid of other decay mode because of their small branching ratios. The most dangerous background is the K0L-> pi0pi0 decay mode. K0L-> pi0pi0 decay creates 4gammas. The trouble is that if 2gammas among 4gammas are lost at K0L-> pi0pi0 decay mode, we cannot distinguish K0L ->pi0nu~nu from K0L-> pi0pi0.
A pi0 detector system needs a hole to pass through secondary neutral particles which are created at the K0L production target. So, we must develop a beam catcher which is willing to veto the gamma on beam line. As a requirement of this beam catcher, it has to have strong efficiency to gammas. But because of it is on the beam line, it needs no efficiency to neutrons. As a prototype of this beam catcher, we developed an Aerogel Cherenkov type counter and tested it. In conclusion, the radiation effect to protons was larger than assumed.
It is considered that light is influenced by Nitrogen scintillation. The purpose of this study is to confirm the provability of Nitrogen scintillation on the Aerogel Cherenkov beam catcher and calibration of the best suited gas.
We study three things.
1. Cabibbo-KOBAYASHI-MASKAWA matrix
2. Theory of scintillation. In particular, we examine the Bethe-Bloch formula and Quenching
mechanism. The Bethe-Bloch formula describes the behavior of passage radiation particles from the matter and energy loss.
3. Experiment of Nitrogen scintillation