Measurement of the Branching Fraction Ratios R(D^{+}) and R(D^{*+}) Using Muonic τ Decays

Abstract

The branching fraction ratios of (B) over bar (0) -> D+tau(-)(v) over bar (tau) and (B) over bar (0) -> D*(+)tau(-)(v) over bar (tau) decays are measured with respect to their muonic counterparts, using a data sample corresponding to an integrated luminosity of 2.0 fb(-1) collected by the LHCb experiment in proton-proton collisions at root s = 13 TeV. The reconstructed final states are formed by combining D+ mesons with tau(-) -> mu(-) (v) over bar (mu)(v) over bar (tau) candidates, where the D+ is reconstructed via the D+ -> K- pi(+) pi(+) decay. The results are R(D+) = 0.249 +/- 0.043 +/- 0.047, R(D*(+)) = 0.402 +/- 0.081 +/- 0.085, where the first uncertainties are statistical and the second systematic. The two measurements have a correlation coefficient of -0.39 and are compatible with the standard model.