Hirose S. et al.Iijima, T.T.IijimaAdachi, I.I.AdachiAdamczyk, K.K.AdamczykAihara, H.H.AiharaAl Said, S.S.Al SaidAsner, D.M.D.M.AsnerAtmacan, H.H.AtmacanAulchenko, V.V.AulchenkoAushev, T.T.AushevPAO-TI CHANGWEI-SHU HOUMIN-ZU WANG2021-07-282021-07-282017319007https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019758244&doi=10.1103%2fPhysRevLett.118.211801&partnerID=40&md5=5516b58b6870ec29cddd8b3622e7bb20https://scholars.lib.ntu.edu.tw/handle/123456789/574726We report the first measurement of the τ lepton polarization Pτ(D?) in the decay B→D?τ-ντ as well as a new measurement of the ratio of the branching fractions R(D?)=B(B→D?τ-ντ)/B(B→D?-ν), where - denotes an electron or a muon, and the τ is reconstructed in the modes τ-→π-ντ and τ-→ρ-ντ. We use the full data sample of 772×106 BB pairs recorded with the Belle detector at the KEKB electron-positron collider. Our results, Pτ(D?)=-0.38±0.51(stat)-0.16+0.21(syst) and R(D?)=0.270±0.035(stat)-0.025+0.028(syst), are consistent with the theoretical predictions of the standard model. ? 2017 American Physical Society.Elementary particles; Belle detectors; Branching fractions; Data sample; The standard model; Polarization; article; lepton; polarization; positron; prediction; theoretical studyjournal article10.1103/PhysRevLett.118.211801285986632-s2.0-85019758244