Measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$ with a semileptonic tagging method
Creators: name: Caria, G.
name: Urquijo, P.
name: Adachi, I.
name: Aihara, H.
name: Said, S. Al
name: Asner, D. M.
name: Atmacan, H.
name: Aushev, T.
name: Babu, V.
name: Badhrees, I.
name: Bakich, A. M.
name: Behera, P.
name: Beleño, C.
name: Bennett, J.
name: Bhuyan, B.
name: Bilka, T.
name: Biswal, J.
name: Bračko, M.
name: Browder, T. E.
name: Campajola, M.
name: Červenkov, D.
name: Chang, P.
name: Cheaib, R.
name: Chekelian, V.
name: Chen, A.
name: Cheon, B. G.
name: Chilikin, K.
name: Cho, H. E.
name: Cho, K.
name: Choi, Y.
name: Choudhury, S.
name: Cinabro, D.
name: Cunliffe, S.
name: Dash, N.
name: De Nardo, G.
name: Di Capua, F.
name: Di Carlo, S.
name: Doležal, Z.
name: Dong, T. V.
name: Eidelman, S.
name: Epifanov, D.
name: Fast, J. E.
name: Ferber, T.
name: Ferlewicz, D.
name: Fulsom, B. G.
name: Garg, R.
name: Gaur, V.
name: Gabyshev, N.
name: Garmash, A.
name: Giri, A.
name: Goldenzweig, P.
name: Greenwald, D.
name: Grzymkowska, O.
name: Guan, Y.
name: Hartbrich, O.
name: Hayasaka, K.
name: Hayashii, H.
name: Higuchi, T.
name: Hou, W. -S.
name: Hsu, C. -L.
name: Inami, K.
name: Inguglia, G.
name: Ishikawa, A.
name: Itoh, R.
name: Iwasaki, M.
name: Iwasaki, Y.
name: Jacobs, W. W.
name: Jeon, H. B.
name: Jia, S.
name: Jin, Y.
name: Joffe, D.
name: Joo, K. K.
name: Kaliyar, A. B.
name: Kang, K. H.
name: Karyan, G.
name: Kawasaki, T.
name: Kichimi, H.
name: Kim, C. H.
name: Kim, D. Y.
name: Kim, H. J.
name: Kim, K. T.
name: Kim, S. H.
name: Kinoshita, K.
name: Kodyš, P.
name: Korpar, S.
name: Kotchetkov, D.
name: Kroeger, R.
name: Krokovny, P.
name: Kumar, R.
name: Kwon, Y. -J.
name: Lange, J. S.
name: Lee, I. S.
name: Lee, J. K.
name: Lee, S. C.
name: Li, L. K.
name: Li, Y. B.
name: Gioi, L. Li
name: Libby, J.
name: Lieret, K.
name: Liventsev, D.
name: Luo, T.
name: Masuda, M.
name: Matsuda, T.
name: Matvienko, D.
name: Merola, M.
name: Metzner, F.
name: Miyabayashi, K.
name: Mohanty, G. B.
name: Moon, T. J.
name: Mori, T.
name: Mussa, R.
name: Nakamura, K. R.
name: Nath, K. J.
name: Nayak, M.
name: Nisar, N. K.
name: Nishida, S.
name: Nishimura, K.
name: Ogawa, K.
name: Ono, H.
name: Onuki, Y.
name: Oskin, P.
name: Pakhlov, P.
name: Pakhlova, G.
name: Pal, B.
name: Pang, T.
name: Park, H.
name: Park, S. -H.
name: Patra, S.
name: Paul, S.
name: Pedlar, T. K.
name: Pestotnik, R.
name: Piilonen, L. E.
name: Popov, V.
name: Prencipe, E.
name: Prim, M. T.
name: Rabusov, A.
name: Resmi, P. K.
name: Ritter, M.
name: Russo, G.
name: Sahoo, D.
name: Sandilya, S.
name: Santelj, L.
name: Sanuki, T.
name: Schneider, O.
name: Schnell, G.
name: Schueler, J.
name: Schwanda, C.
name: Seino, Y.
name: Senyo, K.
name: Sevior, M. E.
name: Shebalin, V.
name: Shiu, J. -G.
name: Shwartz, B.
name: Simon, F.
name: Sokolov, A.
name: Solovieva, E.
name: Starič, M.
name: Stottler, Z. S.
name: Sumiyoshi, T.
name: Sutcliffe, W.
name: Takizawa, M.
name: Tamponi, U.
name: Tanida, K.
name: Tenchini, F.
name: Uchida, M.
name: Uglov, T.
name: Uno, S.
name: Usov, Y.
name: Vahsen, S. E.
name: Van Tonder, R.
name: Varner, G.
name: Vossen, A.
name: Waheed, E.
name: Wang, B.
name: Wang, C. H.
name: Wang, M. -Z.
name: Wang, P.
name: Wang, X. L.
name: Watanuki, S.
name: Wiechczynski, J.
name: Won, E.
name: Yamamoto, H.
name: Yang, S. B.
name: Ye, Hua
name: Yin, J. H.
name: Yuan, C. Z.
name: Zhang, Z. P.
name: Zhilich, V.
name: Zhukova, V.
name: Zhulanov, V.
Publisher: name: Deutsches Elektronen-Synchrotron, DESY, Hamburg
Year: 2019

description: The experimental results on the ratios of branching fractions $\mathcal{R}(D) = {\cal B}(\bar{B} \to D \tau^- \bar{\nu}_{\tau})/{\cal B}(\bar{B} \to D \ell^- \bar{\nu}_{\ell})$ and $\mathcal{R}(D^*) = {\cal B}(\bar{B} \to D^* \tau^- \bar{\nu}_{\tau})/{\cal B}(\bar{B} \to D^* \ell^- \bar{\nu}_{\ell})$, where $\ell$ denotes an electron or a muon, show a long-standing discrepancy with the Standard Model predictions, and might hint to a violation of lepton flavor universality. We report a new simultaneous measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$, based on a data sample containing $772 \times 10^6$ $B\bar{B}$ events recorded at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. In this analysis the tag-side $B$ meson is reconstructed in a semileptonic decay mode and the signal-side $\tau$ is reconstructed in a purely leptonic decay. The measured values are $\mathcal{R}(D)= 0.307 \pm 0.037 \pm 0.016$ and $\mathcal{R}(D^*) = 0.283 \pm 0.018 \pm 0.014$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $0.2$, $1.1$ and $0.8$ standard deviations for $\mathcal{R}(D)$, $\mathcal{R}(D^*)$ and their combination, respectively. This work constitutes the most precise measurements of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$ performed to date as well as the first result for $\mathcal{R}(D)$ based on a semileptonic tagging method.