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Measurement of the τ Lepton Polarization and R(D*) in the Decay <mml:math xmlns:mml="...

Authors
S. Hirose,T. Iijima
I. Adachi,K. Adamczyk,H. Aihara,S. Said,D. Asner,H. Atmacan,V. Aulchenko,T. Aushev,R. Ayad,V. Babu,I. Badhrees,A. Bakich,V. Bansal,E. Barberio,P. Behera,M. Berger,B. Bhuyan,J. Biswal,A. Bondar,G. Bonvicini,T. Browder,M. Bračko,D. Červenkov,P. Chang,K. Chen,B. Cheon,K. Chilikin,R. Chistov,K. Cho,Y. Choi,D. Cinabro,M. Danilov,N. Dash,S. Carlo,J. Dingfelder,Z. Doležal,Z. Drásal,D. Dutta,S. Eidelman,D. Epifanov,H. Farhat,J. Fast,T. Ferber,B. Fulsom,V. Gaur,N. Gabyshev,A. Garmash,P. Goldenzweig,B. Golob,D. Greenwald,J. Grygier,J. Haba,K. Hara,J. Hasenbusch,K. Hayasaka,H. Hayashii,T. Higuchi,W.-S. Hou,C.-L. Hsu,K. Inami,G. Inguglia,A. Ishikawa,R. Itoh,Y. Iwasaki,W. Jacobs,I. Jaeglé,Y. Jin,D. Joffe,K. Joo,T. Julius,Yuji Katō,T. Kawasaki,H. Kichimi,C. Kiesling,D. Kim,J. Kim,K. Kim,M. Kim,S. Kim,K. Kinoshita,P. Kodyš,S. Korpar,D. Kotchetkov,P. Križan,P. Krokovny,T. Kuhr,R. Kulasiri,R. Kumar,Y.-J. Kwon,J. Lange,Y. Li,L. Li,L. Gioi,J. Libby,D. Liventsev,M. Lubej,T. Luo,J. MacNaughton,M. Masuda,T. Matsuda,D. Matvienko,K. Miyabayashi,H. Miyake,H. Miyata,R. Mizuk,G. Mohanty,H. Moon,T. Mori,R. Mussa,M. Nakao,T. Nanut,K. Nath,S. Nishida,M. Nayak,M. Niiyama,N. Nisar,S. Ogawa,S. Okuno,H. Ono,Y. Onuki,W. Ostrowicz,P. Pakhlov,B. Pal,C. Park,H. Park,S. Paul,L. Pesántez,R. Pestotnik,L. Piilonen,K. Prasanth,M. Ritter,A. Rostomyan,M. Różańska,Y. Sakai,S. Sandilya,L. Šantelj,T. Sanuki,Y. Sato,V. Savinov,T. Schlüter,O. Schneider,C. Schwanda,Y. Seino,K. Senyo,O. Seon,M. Sevior,V. Shebalin,C. Shen,T.-A. Shibata,J.-G. Shiu,F. Simon,A. Sokolov,E. Solovieva,M. Starič,J. Strube,K. Sumisawa,T. Sumiyoshi,M. Takizawa,U. Tamponi,F. Tenchini,K. Trabelsi,M. Uchida,T. Uglov,Y. Unno,S. Uno,P. Urquijo,Y. Usov,C. Hulse,G. Varner,K. Varvell,A. Vossen,C. Wang,M.-Z. Wang,P. Wang,M. Watanabe,Y. Watanabe,E. Widmann,E. Won,Y. Yamashita,H. Ye,J. Yelton,C. Yuan,Z. Zhang,V. Zhilich,V. Zhulanov,A. Zupanc,D. Hirschbuehl,Jyoti Biswal,Kai-Feng Chen,Zdeněk Doležal,J. Dorfan,Peter Kodyš,Ramandeep Kumar,C. Li
+194 authors
,Z. Liang
Published
May 26, 2017
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Abstract

We report the first measurement of the $\tau$ lepton polarization $P_\tau(D^*)$ in the decay $\bar{B} \rightarrow D^* \tau^- \bar{\nu}_\tau$ as well as a new measurement of the ratio of the branching fractions $R(D^{*}) = \mathcal{B}(\bar {B} \rightarrow D^* \tau^- \bar{\nu}_\tau) / \mathcal{B}(\bar{B} \rightarrow D^* \ell^- \bar{\nu}_\ell)$, where $\ell^-$ denotes an electron or a muon, and the $\tau$ is reconstructed in the modes $\tau^- \rightarrow \pi^- \nu_\tau$ and $\tau^- \rightarrow \rho^- \nu_\tau$. We use the full data sample of $772 \times 10^6$ $B{\bar B}$ pairs recorded with the Belle detector at the KEKB electron-positron collider. Our results, $P_\tau(D^*) = -0.38 \pm 0.51 {\rm (stat.)} ^{+0.21}_{-0.16} {\rm (syst.)}$ and $R(D^*) = 0.270 \pm 0.035{\rm (stat.)} ^{+0.028}_{-0.025}{\rm (syst.)}$, are consistent with the theoretical predictions of the Standard Model.

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