Experimental upper limits on branching fractions for unexpected decay modes of the τ lepton

Searches for 12 neutrinoless decay modes of the which violate lepton-number conservation have been made using the reaction e+e-+-. No evidence for lepton-number violation is observed, and we have set upper limits (90% C.L.) on the branching ratio for each decay mode. The branching-ratio limits on the radiative decays and e are 0.055 and 0.064%, respectively. For the charged lepton decays ee, eee, and, the branching ratio limits are 0.040, 0.033, 0.044, and 0.049%, respectively. Upper limits on the branching ratios for the following charged lepton + neutral hadron decays are 0 (0.037%), 0 (0.044%), eK0 (0.13%), K0 (0.10%), 0 (0.21%), and 0 (0.082%). We also use these data to search for the pair production in e+e- annihilation of some unconventional particles with masses less than about 3 GeV/c2. © 1982 The American Physical Society.