Detection and analysis of tau-neutrino interactions in DONUT emulsion target

The DONUT experiment used an emulsion/counter-hybrid-detector, which succeeded in detecting tau-neutrino charged-current interactions. A new method of emulsion analysis, NETSCAN, was used to locate neutrino events and detect tau decays. It is based on a fully automated emulsion readout system (Ultra Track Selector) developed at Nagoya University. The achieved plate-to-plate alignment accuracy of similar to0.2 mum over an area of 2.6 mm x 2.6 mm permitted an efficient and systematic tau decay search using emulsion data. Moreover, this accuracy allowed measurement of particle momenta by multiple Coulomb scattering, and contributed to the efficient background rejection for the v, candidates. This paper describes details of our emulsion analysis methods. (C) 2002 Elsevier Science B.V. All rights reserved.