Research for neutrino oscillation by direct detection of tau-lepton

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Ultra Track selector (UTS) will make big change of the usage of the emulsion.The CHORUS experiment is organized to study the mass of tau-neutrino using mu-neutrmno to tau-neutrino oscillation . The emulsion target was used to detect neutrino interactions and to recognize the tau-neutrmno from other neutrinos.The first automatic emulsion scanning system (New Track Selector) was developed. Up to now, lOOK neutrino interactions were located in the emulsion and were analyzed short fight decays in emulsion targets. The tau decay search was at first focused on the decay channel of nu_<mu>*nu_<tau>, this channel has almost no background. We found zero tau-neutrino interaction and obtained the mixing limit of mu to tau sin^2 (2theta@mutau@E2) >O.OO1, (for DELTAm^2 > 10eV^2) . This result is not contradict to Super-K result which was recently presented in conference of Neutrino physics and Astrophysics (NEUTRINO'98) at Takayama city. Our result is 5 times better than the past world record E531 in FNAL 1978.Recently we finished the development of "Ultra fast Track Selector" which has 10 times faster than "New Track Selector".