101. Measurement of the Ratio of Partial Branching Fractions of Inclusive $\overline{B} \to X_u \ell \overline{\nu}$ to $\overline{B} \to X_{c} \ell \overline{\nu}$ and the Ratio of their Spectra with Hadronic Tagging
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Belle Collaboration, Hohmann, M., Urquijo, P., Adachi, I., Aihara, H., Asner, D. M., Aushev, T., Ayad, R., Babu, V., Banerjee, Sw., Bauer, M., Bennett, J., Bernlochner, F., Bessner, M., Bhuyan, B., Bilka, T., Biswas, D., Bobrov, A., Bodrov, D., Bonvicini, G., Borah, J., Bozek, A., Bračko, M., Branchini, P., Browder, T. E., Budano, A., Campajola, M., Cao, L., Chang, M. -C., Cheon, B. G., Cho, K., Choi, S. -K., Choi, Y., Das, S., Dash, N., De Nardo, G., De Pietro, G., Dhamija, R., Dingfelder, J., Doležal, Z., Dong, T. V., Dubey, S., Ecker, P., Ferber, T., Ferlewicz, D., Frey, A., Fulsom, B. G., Gaur, V., Giri, A., Goldenzweig, P., Graziani, E., Gu, T., Gudkova, K., Hadjivasiliou, C., Hartbrich, O., Hayasaka, K., Hayashii, H., Hazra, S., Hedges, M. T., Herrmann, D., Hou, W. -S., Hsu, C. -L., Inami, K., Ishikawa, A., Itoh, R., Iwasaki, M., Jacobs, W. W., Ji, Q. P., Jia, S., Jin, Y., Kawasaki, T., Kiesling, C., Kim, D. Y., Kim, K. -H., Kim, Y. -K., Kinoshita, K., Korobov, A., Kovalenko, E., Križan, P., Kuhr, T., Kumar, M., Kumar, R., Kumara, K., Kwon, Y. -J., Lam, T., Laurenza, M., Lee, S. C., Levit, D., Lewis, P., Li, L. K., Gioi, L. Li, Liventsev, D., Masuda, M., Matsuda, T., Matvienko, D., Maurya, S. K., Meier, F., Merola, M., Metzner, F., Mizuk, R., Miyabayashi, K., Mohanty, G. B., Mussa, R., Nakao, M., Natkaniec, Z., Natochii, A., Nayak, L., Nishida, S., Ogawa, S., Ono, H., Oskin, P., Pakhlova, G., Pardi, S., Park, H., Park, J., Park, S. -H., Passeri, A., Patra, S., Paul, S., Pedlar, T. K., Pestotnik, R., Piilonen, L. E., Podobnik, T., Prencipe, E., Prim, M. T., Röhrken, M., Rozanska, M., Russo, G., Sandilya, S., Savinov, V., Schnell, G., Schwanda, C., Schwartz, A. J., Seino, Y., Senyo, K., Shan, W., Sharma, C., Shiu, J. -G., Shwartz, B., Solovieva, E., Starič, M., Sumihama, M., Sumisawa, K., Takizawa, M., Tanida, K., Tenchini, F., Trabelsi, K., Uchida, M., Uno, S., Vahsen, S. E., Varvell, K. E., Vinokurova, A., Wang, M. -Z., Won, E., Yabsley, B. D., Yan, W., Yang, S. B., Yook, Y., Zhilich, V., and Zhukova, V.
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High Energy Physics - Experiment - Abstract
We present a measurement of the ratio of partial branching fractions of the semi-leptonic inclusive decays, $\overline{B} \to X_{u} \ell \overline{\nu}$ to $\overline{B} \to X_{c} \ell \overline{\nu}$, where $\ell = (e, \mu)$, using the full Belle sample of $772 \times 10^{6}$ $B \kern 0.18em\overline{\kern -0.18em B}$ pairs collected at the $\Upsilon(4S)$ resonance. The ratio is measured via a two-dimensional fit to the squared four-momentum transfer to the lepton pair, and the charged lepton energy in the $B$ meson rest frame, where the latter must be larger than $1$ Ge\kern -0.1em V, covering approximately $86\%$ and $78\%$ of the $\overline{B} \to X_{u} \ell \overline{\nu}$ and $\overline{B} \to X_{c} \ell \overline{\nu}$ phase space, respectively. We find $\Delta \mathcal{B}(\overline{B} \to X_{u} \ell \overline{\nu})/ \Delta \mathcal{B}(\overline{B} \to X_{c} \ell \overline{\nu}) = 0.0196(1 \pm 8.4\%_{\rm stat} \pm 7.9\%_{\rm syst})$ where the uncertainties are statistical and systematic, respectively. In addition, we report the partial branching fractions separately for charged and neutral $B$ meson decays, and for electron and muon decay channels. We place a limit on isospin breaking in $\overline{B} \to X_{u} \ell \overline{\nu}$ decays, and find no indication of lepton flavor universality violation in either the charmed or charmless mode. Furthermore, we unfold the $\overline{B} \to X_{u} \ell \overline{\nu}$ and $\overline{B} \to X_{c} \ell \overline{\nu}$ yields and report the differential ratio in lepton energy and four-momentum transfer squared., Comment: 22 pages, 13 figures
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- 2023