Measurement of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>τ</mml:mi></mml:mrow></mml:math> Lepton Polarization and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>R</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:msup><mml:mrow><mml:mi>D</mml:mi></mml:mrow><mml:mrow><mml:mo>*</mml:mo></mml:mrow></mml:msup><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math> in the Decay <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mover accent="true"><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mrow><mml:mo stretchy="false">¯</mml:mo></mml:mrow></mml:mover><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mrow><mml:mi>D</mml:mi></mml:mrow><mml:mrow><mml:mo>*</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>τ</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup><mml:msub><mml:mrow><mml:mover accent="true"><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mo stretchy="false">¯</mml:mo></mml:mrow></mml:mover></mml:mrow><mml:mrow><mml:mi>τ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>
S. Hirose(Nagoya University), T. Iijima(Nagoya University), I. Adachi(High Energy Accelerator Research Organization), K. Adamczyk(Institute of Nuclear Physics, Polish Academy of Sciences), H. Aihara(The University of Tokyo), S. Al Said(King Abdulaziz University), D. M. Asner(Pacific Northwest National Laboratory), H. Atmacan(Middle East Technical University), V. Aulchenko(Novosibirsk State University), T. Aushev(Moscow Institute of Physics and Technology), R. Ayad(University of Tabuk), V. Babu(Tata Institute of Fundamental Research), I. Badhrees(King Abdulaziz City for Science and Technology), A. M. Bakich(The University of Sydney), V. Bansal(Pacific Northwest National Laboratory), E. L. Barberio(The University of Melbourne), P. K. Behera(Indian Institute of Technology Madras), M. Berger(Stefan Meyer Institute for Subatomic Physics), B. Bhuyan(Indian Institute of Technology Guwahati), J. P. Biswal(Jožef Stefan Institute), A. Bondar(Novosibirsk State University), G. Bonvicini(Wayne State University), A. Bożek(Institute of Nuclear Physics, Polish Academy of Sciences), M. Bračko(Jožef Stefan Institute), T. E. Browder(University of Hawaiʻi at Mānoa), D. Červenkov(Charles University), P. Chang(National Taiwan University), K. F. Chen(National Central University), B. G. Cheon(Hanyang University), K. Chilikin(P.N. Lebedev Physical Institute of the Russian Academy of Sciences), R. Chistov(P.N. Lebedev Physical Institute of the Russian Academy of Sciences), K. Cho(Korea Institute of Science & Technology Information), Y. Choi(Sungkyunkwan University), D. Cinabro(Wayne State University), M. Danilov(P.N. Lebedev Physical Institute of the Russian Academy of Sciences), N. Dash(Indian Institute of Technology Bhubaneswar), S. Di Carlo(Wayne State University), J. Dingfelder(University of Bonn), Z. Doležal(Charles University), Z. Drásal(Charles University), D. Dutta(Tata Institute of Fundamental Research), S. Eidelman(Novosibirsk State University), D. Epifanov(Novosibirsk State University), H. Farhat(Wayne State University), J. E. Fast(Pacific Northwest National Laboratory), T. Ferber(Deutsches Elektronen-Synchrotron DESY), B. G. Fulsom(Pacific Northwest National Laboratory), V. Gaur(Tata Institute of Fundamental Research), N. Gabyshev(Novosibirsk State University), A. Garmash(Novosibirsk State University), P. Goldenzweig(Karlsruhe Institute of Technology), B. Golob(University of Ljubljana), D. Greenwald(Technical University of Munich), J. Grygier(Karlsruhe Institute of Technology), J. Haba(High Energy Accelerator Research Organization), K. Hara(High Energy Accelerator Research Organization), J. Hasenbusch(University of Bonn), K. Hayasaka(Niigata University), H. Hayashii(Nara Women's University), T. Higuchi(Kavli Institute for the Physics and Mathematics of the Universe), W.-S. Hou(National Taiwan University), C.-L. Hsu(The University of Melbourne), K. Inami(Nagoya University), G. Inguglia(Deutsches Elektronen-Synchrotron DESY), A. Ishikawa(Tohoku University), R. Itoh(High Energy Accelerator Research Organization), Y. Iwasaki(High Energy Accelerator Research Organization), W. W. Jacobs(Indiana University Bloomington), I. Jaeglé(University of Florida), Y. Jin(The University of Tokyo), D. Joffe(Kennesaw State University), K. K. Joo(Chonnam National University), T. Julius(The University of Melbourne), Yuji Katō(Nagoya University), T. Kawasaki(Niigata University), H. Kichimi(High Energy Accelerator Research Organization), C. Kiesling(Max Planck Institute for Physics), D. Y. Kim(Soongsil University), J. B. Kim(Korea University), K. T. Kim(Korea University), M. J. Kim(Kyungpook National University), S. H. Kim(Hanyang University), K. Kinoshita(University of Cincinnati), P. Kodyš(Charles University), S. Korpar(Jožef Stefan Institute), D. Kotchetkov(University of Hawaiʻi at Mānoa), P. Križan(University of Ljubljana), P. Krokovny(Novosibirsk State University), T. Kuhr(Ludwig-Maximilians-Universität München), R. Kulasiri(Kennesaw State University), R. Kumar(Punjab Agricultural University), Y.-J. Kwon(Yonsei University), J. S. Lange(Justus-Liebig-Universität Gießen), C. H. Li(The University of Melbourne), L. Li(University of Science and Technology of China), Y. Li(Virginia Tech), L. Li Gioi(Max Planck Institute for Physics), J. Libby(Indian Institute of Technology Madras), D. Liventsev(High Energy Accelerator Research Organization), M. Lubej(Jožef Stefan Institute), T. Luo(University of Pittsburgh), J. MacNaughton(High Energy Accelerator Research Organization), M. Masuda(Earthquake Engineering Research Institute), T. Matsuda(University of Miyazaki), D. Matvienko(Novosibirsk State University), K. Miyabayashi(Nara Women's University), H. Miyake(High Energy Accelerator Research Organization), H. Miyata(Niigata University), R. Mizuk(P.N. Lebedev Physical Institute of the Russian Academy of Sciences), G. B. Mohanty(Tata Institute of Fundamental Research), H. K. Moon(Korea University), T. Mori(Nagoya University), R. Mussa(Istituto Nazionale di Fisica Nucleare, Sezione di Torino), M. Nakao(High Energy Accelerator Research Organization), T. Nanut(Jožef Stefan Institute), K. J. Nath(Indian Institute of Technology Guwahati), Z. Natkaniec(Institute of Nuclear Physics, Polish Academy of Sciences), M. Nayak(High Energy Accelerator Research Organization), M. Niiyama(Kyoto University), N. K. Nisar(University of Pittsburgh), S. Nishida(High Energy Accelerator Research Organization), S. Ogawa(Toho University), S. Okuno(Kanagawa University), H. Ono(Nippon Dental University), Y. Onuki(The University of Tokyo), W. Ostrowicz(Institute of Nuclear Physics, Polish Academy of Sciences), P. Pakhlov(P.N. Lebedev Physical Institute of the Russian Academy of Sciences), G. Pakhlova(P.N. Lebedev Physical Institute of the Russian Academy of Sciences), B. Pal(University of Cincinnati), C. W. Park(Sungkyunkwan University), H. Park(Kyungpook National University), S. Paul(Technical University of Munich), L. Pesántez(University of Bonn), R. Pestotnik(Jožef Stefan Institute), L. E. Piilonen(Virginia Tech), K. Prasanth(Indian Institute of Technology Madras), M. Ritter(Ludwig-Maximilians-Universität München), A. Rostomyan(Deutsches Elektronen-Synchrotron DESY), M. Różańska(Institute of Nuclear Physics, Polish Academy of Sciences), Y. Sakai(High Energy Accelerator Research Organization), S. Sandilya(University of Cincinnati), L. Šantelj(High Energy Accelerator Research Organization), T. Sanuki(Tohoku University), Y. Sato(Nagoya University), V. Savinov(University of Pittsburgh), T. Schlüter(Ludwig-Maximilians-Universität München), O. Schneider(École Polytechnique Fédérale de Lausanne), G. Schnell(Ikerbasque), C. Schwanda, Y. Seino(Niigata University), K. Senyo(Yamagata University), O. Seon(Nagoya University), M. E. Sevior(The University of Melbourne), V. Shebalin(Novosibirsk State University), C. P. Shen(Beihang University), T.-A. Shibata(Tokyo Institute of Technology), J.-G. Shiu(National Taiwan University), F. Simon(Max Planck Institute for Physics), A. Sokolov(Institute for High Energy Physics), E. Solovieva(P.N. Lebedev Physical Institute of the Russian Academy of Sciences), M. Starič(Jožef Stefan Institute), J. Strube(Pacific Northwest National Laboratory), K. Sumisawa(High Energy Accelerator Research Organization), T. Sumiyoshi(Tokyo Metropolitan University), M. Takizawa(High Energy Accelerator Research Organization), U. Tamponi(Istituto Nazionale di Fisica Nucleare, Sezione di Torino), F. Tenchini(The University of Melbourne), K. Trabelsi(High Energy Accelerator Research Organization), M. Uchida(Tokyo Institute of Technology), T. Uglov(P.N. Lebedev Physical Institute of the Russian Academy of Sciences), Y. Unno(Hanyang University), S. Uno(High Energy Accelerator Research Organization), P. Urquijo(The University of Melbourne), Y. Ushiroda(High Energy Accelerator Research Organization), Y. Usov(Novosibirsk State University), C. Van Hulse(University of the Basque Country), G. Varner(University of Hawaiʻi at Mānoa), K. E. Varvell(The University of Sydney), A. Vossen(Indiana University Bloomington), C. H. Wang(National United University), M.-Z. Wang(National Taiwan University), P. Wang(Chinese Academy of Sciences), M. Watanabe(Niigata University), Y. Watanabe(Kanagawa University), E. Widmann(Stefan Meyer Institute for Subatomic Physics), E. Won(Korea University), Y. Yamashita(Nippon Dental University), H. Ye(Deutsches Elektronen-Synchrotron DESY), J. Yelton(University of Florida), C. Z. Yuan(Chinese Academy of Sciences), Z. P. Zhang(University of Science and Technology of China), V. Zhilich(Novosibirsk State University), V. Zhulanov(Novosibirsk State University), A. Zupanc(University of Ljubljana)
Cited by 486Open Access
Abstract
We report the first measurement of the $\ensuremath{\tau}$ lepton polarization ${P}_{\ensuremath{\tau}}({D}^{*})$ in the decay $\overline{B}\ensuremath{\rightarrow}{D}^{*}{\ensuremath{\tau}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ as well as a new measurement of the ratio of the branching fractions $R({D}^{*})=\mathcal{B}(\overline{B}\ensuremath{\rightarrow}{D}^{*}{\ensuremath{\tau}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}})/\mathcal{B}(\overline{B}\ensuremath{\rightarrow}{D}^{*}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})$, where ${\ensuremath{\ell}}^{\ensuremath{-}}$ denotes an electron or a muon, and the $\ensuremath{\tau}$ is reconstructed in the modes ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ and ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$. We use the full data sample of $772\ifmmode\times\else\texttimes\fi{}1{0}^{6}\text{ }\text{ }B\overline{B}$ pairs recorded with the Belle detector at the KEKB electron-positron collider. Our results, ${P}_{\ensuremath{\tau}}({D}^{*})=\ensuremath{-}0.38\ifmmode\pm\else\textpm\fi{}0.51{(\text{stat})}_{\ensuremath{-}0.16}^{+0.21}(\text{syst})$ and $R({D}^{*})=0.270\ifmmode\pm\else\textpm\fi{}0.035{(\text{stat})}_{\ensuremath{-}0.025}^{+0.028}(\text{syst})$, are consistent with the theoretical predictions of the standard model.
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