With the full data sample of 772×106 B¯B pairs recorded by the Belle detector at the KEKB electron-positron collider, the decay ¯B→D∗τ−¯ντ is studied with the hadronic τ decays τ−→π−ντ and τ−→ρ−ντ. The τ polarization Pτ(D∗) in two-body hadronic τ decays is measured, as well as the ratio of the branching fractions R(D∗)=B(¯B→D∗τ−¯ντ)/B(¯B→D∗ℓ−¯νℓ), where ℓ− denotes an electron or a muon. Our results, Pτ(D∗)=−0.38±0.51(stat)+0.21−0.16(syst) and R(D∗)=0.270±0.035(stat)+0.028−0.025(syst), are consistent with the theoretical predictions of the standard model. The polarization values of Pτ(D∗)>+0.5 are excluded at the 90% confidence level.
Physical Review D
Digital Object Identifier (DOI)
et al., S. Hirose and Kulasiri, Ratnappuli L., "Measurement of the τ lepton polarization and R ( D ∗ ) in the decay ¯ B → D ∗ τ − ¯ ν τ with one-prong hadronic τ decays at Belle" (2018). Faculty Publications. 4195.