D0-Ds lifetime difference and τ→7π+ντ decays -: art. no. 034018

In this paper we discuss some aspects of the inclusive decays of charmed mesons and also decays of the tau lepton into nu(tau) + 7pi. We find that phase space effects are likely to explain the observed lifetime ratio tau(D-s(+))/tau(D-0) = 1.17. In particular one need not appeal to a large annihilation contribution in the inclusive D-0 decay which, being absent in D-s(+) decays, could also contribute to the enhanced D-0 decay rate relative to that of the D-s(+). Examining a separate problem, we find that the rate for tau-->nu(tau) + 7pi is almost completely dominated by the tiny phase space for the final eight particle state. Using an effective chiral Lagrangian to estimate the matrix element yields a branching ratio into the channel of interest far smaller than the present upper bound.