The measurement of a tau-neutorino mass

点击翻译按钮获取中文摘要

CHORUS is the international project using the neutrino beam from super proton synchrotrn (SPS) of CERN (Center of Europ organization for Research of Nuclus). The object of this project is to observe the mass of tau-neutrino by the method of the oscillation from mu-neutrino to tau-neutrino. The identification of tau-neutrino could be done by detecting the produced tau by observing the trace of tau from produced point to the decay point in the photographic nucler emulsion.The detecter have many parts, target spectrometer calorimeter and muon spectrometer. We are contributing on the target the most important target of this experiment. This target has the sandwich structure of emulsion sheets and fiber trackers.The neutrino exposure has been finished on Novenber in 1995. The emulsion analysis, the most difficult job in this project, has been done by using Automatic emulsion analysis system originally developed by physists of Nagoya university. The number of analyzed neutrino interaction in the emulsion is more than 7700 neutorino interactions by 4 month scanning. This number is about 15% of all CHORUS, but already this number is 2 times higher than the most sensitive similler experiment, named E531 done in 1978. This experiment is sensitive to 1 eV in tauneutrino mass and 1% in mixing tau-neutrino to mu-neutrino.To finish all of the analysis, it take more two years.