2016/12/31 by S. Hirose, T. Iijima, I. Adachi +201
Chemistry · Physics and Astronomy · #Bar (unit) #Chemistry #Collider #Crystallography #Dark Matter and Cosmic Phenomena #Electron #Electron–positron annihilation #Hadron #KEKB #Lepton #Muon #Neutrino Physics Research #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Physics #hep-ex
paper · pdf · doi:10.1103/physrevlett.118.211801
published as Phys. Rev. Lett. 118, 211801 (2017) · 7 pages, 2 figures, submitted to Physical Review Letters; one figure was removed from the first version
openalex created_date 2016/12/16 · arxiv created 2017/05/03 · openalex publication_date 2017/05/26 · arxiv updated 2017/05/30 · openalex updated_date 2026/08/05
We report the first measurement of the \ensuremathτ lepton polarization P_\ensuremathτ(D*) in the decay B\ensuremath→D*\ensuremathτ^\ensuremath-\ensuremathν_\ensuremathτ as well as a new measurement of the ratio of the branching fractions R(D*)=B(B\ensuremath→D*\ensuremathτ^\ensuremath-\ensuremathν_\ensuremathτ)/B(B\ensuremath→D*\ensuremathℓ^\ensuremath-\ensuremathν_\ensuremathℓ), where \ensuremathℓ^\ensuremath- denotes an electron or a muon, and the \ensuremathτ is reconstructed in the modes \ensuremathτ^\ensuremath-\ensuremath→\ensuremathπ^\ensuremath-\ensuremathν_\ensuremathτ and \ensuremathτ^\ensuremath-\ensuremath→\ensuremathρ^\ensuremath-\ensuremathν_\ensuremathτ. We use the full data sample of 772\ifmmode×\else\texttimes\fi106 BB pairs recorded with the Belle detector at the KEKB electron-positron collider. Our results, P_\ensuremathτ(D*)=\ensuremath-0.38\ifmmode±\else\textpm\fi0.51(stat)_\ensuremath-0.16+0.21(syst) and R(D*)=0.270\ifmmode±\else\textpm\fi0.035(stat)_\ensuremath-0.025+0.028(syst), are consistent with the theoretical predictions of the standard model.