Measurement of the π lepton polarization and R(D*) in the decay B⁻ → D* π⁻V⁻ π with one-prong hadronic π decays at Belle

S. Hirose, T. Iijima, I. Adachi, K. Adamczyk, H. Aihara, S. Al Said, D. M. Asner, H. Atmacan, T. Aushev, R. Ayad, T. Aziz, V. Babu (+172 others)
With the full data sample of 772 × 10 6 BB pairs recorded by the Belle detector at the KEKB electronpositron collider, the decayB → D Ã τ −ν τ is studied with the hadronic τ decays τ − → π − ν τ and τ − → ρ − ν τ . The τ polarization P τ ðD Ã Þ in two-body hadronic τ decays is measured, as well as the ratio of the branching fractions where l − denotes an electron or a muon. Our results, P τ ðD Ã Þ ¼ −0.38 AE 0.51ðstatÞ þ0.21 −0.16 ðsystÞ and RðD Ã Þ ¼ 0.270 AE 0.035ðstatÞ þ0.028 −0.025 ðsystÞ,
more » ... 028 −0.025 ðsystÞ, are consistent with the theoretical predictions of the standard model. The polarization values of P τ ðD Ã Þ > þ0.5 are excluded at the 90% confidence level.
doi:10.5445/ir/1000079283 fatcat:6lq3774djzdirhzyovmt2dgod4