Tau lepton emission in two-nucleon disappearance reactions from within nuclei which conserve baryon number minus lepton number (B-L) is considered. It is shown that some existing limits on proton decay channels and two-nucleon disappearance reactions resulting in electrons and muons can be applied to $\Delta B=\Delta L=2$ decays involving $\tau$ leptons. For the two-nucleon disappearance channel $np\to\tau^+ \overline\nu_\tau$ the estimated limit for the partial mean life is $\frac{ \tau}{ Br}>1\times10^{ 30}$ yrs based on results from the IMB3 experiment. Re-analysis of existing data and future experiments could result in higher sensitivity for two-nucleon disappearance modes involving $\tau$ lepton final states.
Categories: hep-ex hep-ph
