the Fr jus experiment on nucleon decay modes leptons

Lower limits on the nucleon lifetime in channels containing at least one positron or muon are given. The analysis is based on 4 years of data taking with the Fr6jus detector. Various approaches to determine the back- ground from atmospheric neutrinos are discussed and two different nuclear models are used in event simula- tions. The limits obtained range from 1031 years for p--*e+K *~ to 1.5-1032 years for p~/z+y.