Measurement of the Absolute Branching Fraction of D-s(+) -> tau(+)nu(tau) via tau(+) -> e(+)nu(e)(nu)over-bar(tau)

Abstract

Using a dataset of 6.32 fb(-1) of e(+)e(-) annihilation data collected with the BESIII detector at center-ofmass energies between 4178 and 4226 MeV, we have measured the absolute branching fraction of the leptonic decay D-s(+) -> tau(+)nu(tau) via tau(+) -> e(+)nu(e)(nu) over bar (tau), and find BDs+->tau+nu tau = (5.27 +/- 0.10 +/- 0.12) x 10(-2), where the first uncertainty is statistical and the second is systematic. The precision is improved by a factor of 2 compared to the previous best measurement. Combining with fD thorns from lattice quantum chromodynamics calculations or the vertical bar V-cs vertical bar from the CKMfitter group, we extract vertical bar V-cs vertical bar = 0.978 +/- 0.009 +/- 0.012 and f(DS+) = (251.1 +/- 2.4 +/- 3.0) MeV, respectively. Combining our result with the world averages of BDs+->tau+nu tau and BDS+->mu+nu mu, we obtain the ratio of the branching fractions BDS+->tau+nu tau/BDs+->mu+nu mu = 9.72 +/- 0.37, which is consistent with the standard model prediction of lepton flavor universalit