On-line measurement with automatic emulsion analysis system and off-line data processing (E531 neutrino experiment)

The automatic emulsion analysis system developed by Nagoya cosmic ray observation group was practically used for the experiment (FNAL-E531) on determining the lifetime of charm particles for the first time in the world, and achieved a great successful result. The system consists of four large precise coordinate-measuring stages capable of conducting simultaneous measurement and multiple (currently four) DOMS (digitized on-line microscope), supported with one mini-computer (ECLIPS S/130). The purpose of E531 experiment was the determination of charm particle lifetime. The experiment was carried out at FNAL, USA, and by the irradiation of wide band ν sub(μ) beam equivalent to 7 x 1018 of 350 GeV/c protons. The detector was a hybrid system of emulsions and a counter spectrometer. The scan of neutrino reaction, the scan of charm particles, and charm event measurement were analyzed in emulsions, and the on-line programs for-respective analyses were created. Nagoya group has found 726 neutrino reactions in the first run, obtained 37 charm particle candidates, and found 1442 neutrino reactions in the second run, and obtained 56 charm particle candidates. The capability of the automatic emulsion analysis system in terms of the time equired for analysis is in total 3.5 hours per event; 15 minutes for C.S. scan, 15 minutes for coupling to module, 20 minutes for tracing to vertex, 1 hour for neutrino reaction measurement, 10 minutes for offline data processing and 1.5 hours for charm particle scanning. (Wakatsuki, Y.)