Improved Measurement of Absolute Branching Fraction of Ds to tau nu
We have studied the leptonic decay D^+_s to tau^+ nu_tau, via the decay channel tau^+ to e^+ nu_e anti-nu_tau, using a sample of tagged D_s^+ decays collected near the D^*_s D_s peak production energy in e^+ e^- collisions with the CLEO-c detector. We obtain B(D^+_s to tau^+ nu_tau) = (5.30 +- 0.47 +- 0.22) % and determine the decay constant f_Ds = (252.5 +- 11.1 +- 5.2) MeV, where the first uncertainties are statistical and the second are systematic.