Measurement of Angular Coefficients of $\bar{B} \to D^* \ell \barν_\ell$: Implications for $|V_{cb}|$ and Tests of Lepton Flavor Universality

Belle Collaboration, M. T. Prim, F. Bernlochner, F. Metzner, H. Aihara, D. M. Asner, T. Aushev, R. Ayad, V. Babu, Sw. Banerjee, P. Behera, K. Belous, J. Bennett, M. Bessner, V. Bhardwaj, B. Bhuyan, T. Bilka, D. Biswas, D. Bodrov, A. Bondar, J. Borah, M. Bračko, P. Branchini, T. E. Browder, A. Budano, M. Campajola, L. Cao, D. Červenkov, P. Chang, B. G. Cheon, S. -K. Choi, Y. Choi, S. Choudhury, J. Cochran, S. Das, N. Dash, G. De Nardo, G. De Pietro, R. Dhamija, F. Di Capua, Z. Doležal, T. V. Dong, S. Dubey, P. Ecker, D. Epifanov, T. Ferber, D. Ferlewicz, B. G. Fulsom, R. Garg, V. Gaur, A. Giri, P. Goldenz weig, T. Gu, K. Gudkova, C. Hadjivasiliou, T. Hara, H. Hayashii, S. Hazra, M. T. Hedges, D. Herrmann, M. Hernández Villanueva, W. -S. Hou, C. -L. Hsu, K. Inami, G. Inguglia, N. Ipsita, A. Ishikawa, R. Itoh, M. Iwasaki, W. W. Jacobs, C. Kiesling, C. H. Kim, D. Y. Kim, K. -H. Kim, P. Kodyš, T. Konno, A. Korobov, S. Korpar, E. Kovalenko, P. Križan, P. Krokovny, T. Kuhr, M. Kumar, R. Kumar, Y. -J. Kwon, T. Lam, S. C. Lee, P. Lewis, L. K. Li, L. Li Gioi, J. Libby, D. Liventsev, Y. Ma, T. Matsuda, D. Matvienko, S. K. Maurya, F. Meier, M. Merola, K. Miyabayashi, R. Mizuk, G. B. Mohanty, I. Nakamura, M. Nakao, D. Narwal, Z. Natkaniec, A. Natochii, L. Nayak, S. Nishida, H. Ono, P. Oskin, P. Pakhlov, G. Pakhlova, S. -H. Park, A. Passeri, S. Patra, T. K. Pedlar, R. Pestotnik, L. E. Piilonen, T. Podobnik, E. Prencipe, M. Röhrken, N. Rout, G. Russo, S. Sandilya, L. Santelj, V. Savinov, P. Schmolz, G. Schnell, C. Schwanda, Y. Seino, K. Senyo, W. Shan, J. -G. Shiu, J. B. Singh, E. Solovieva, M. Starič, Z. S. Stottler, M. Sumihama, M. Takizawa, K. Tanida, F. Tenchini, R. Tiwary, K. Trabelsi, Y. Unno, S. Uno, P. Urquijo, Y. Usov, S. E. Vahsen, K. E. Varvell, A. Vossen, M. -Z. Wang, X. L. Wang, E. Won, B. D. Yabsley, W. Yan, S. B. Yang, J. H. Yin, L. Yuan, Z. P. Zhang, V. Zhilich, V. Zhukova

Published 2023-10-31Version 1

We measure the complete set of angular coefficients $J_i$ for exclusive $\bar{B} \to D^* \ell \bar{\nu}_\ell$ decays ($\ell = e, \mu$). Our analysis uses the full $711\,\mathrm{fb}^{-1}$ Belle data set with hadronic tag-side reconstruction. The results allow us to extract the form factors describing the $B \to D^*$ transition and the Cabibbo-Kobayashi-Maskawa matrix element $|V_{\rm cb}|$. Using recent lattice QCD calculations for the hadronic form factors, we find $|V_{\rm cb}| = (41.0 \pm 0.7) \times 10^3 $ using the BGL parameterization, compatible with determinations from inclusive semileptonic decays. We search for lepton flavor universality violation as a function of the hadronic recoil parameter $w$, and investigate the differences of the electron and muon angular distributions. We find no deviation from Standard Model expectations.