Test of Light-Lepton Universality in the Rates of Inclusive Semileptonic B -Meson Decays at Belle II

We present the first measurement of the ratio of branching fractions of inclusive semileptonic $B$-meson decays, $R(X_{e/\mu}) = \mathcal{B}(B\to X \, e \, \nu) / \mathcal{B}(B\to X \, \mu \, \nu)$, a precision test of electron-muon universality, using data corresponding to $189\,\mathrm{fb}^{-1}$ f...

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Veröffentlicht in:	Physical review letters 2023-08, Vol.131 (5), p.051804-051804, Article 051804
Hauptverfasser:	Aggarwal, L., Ahmed, H., Aihara, H., Akopov, N., Aloisio, A., Anh Ky, N., Asner, D. M., Atmacan, H., Aushev, T., Aushev, V., Bae, H., Bahinipati, S., Bambade, P., Banerjee, Sw, Bansal, S., Barrett, M., Baudot, J., Bauer, M., Baur, A., Beaubien, A., Becker, J., Bennett, J. V., Bernieri, E., Bernlochner, F. U., Bertacchi, V., Bertemes, M., Bertholet, E., Bessner, M., Bettarini, S., Bhardwaj, V., Bhuyan, B., Bianchi, F., Bilka, T., Bilokin, S., Biswas, D., Bodrov, D., Borah, J., Bozek, A., Bračko, M., Briere, R. A., Browder, T. E., Budano, A., Bussino, S., Campajola, M., Cao, L., Casarosa, G., Cecchi, C., Cerasoli, J., Chang, M.-C., Cheaib, R., Cheema, P., Chekelian, V., Cheon, B. G., Chilikin, K., Chirapatpimol, K., Cho, H.-E., Cho, K., Cho, S.-J., Choi, S.-K., Choudhury, S., Cochran, J., Corona, L., Cunliffe, S., Dattola, F., De La Cruz-Burelo, E., De La Motte, S. A., De Nardo, G., De Nuccio, M., De Pietro, G., de Sangro, R., Destefanis, M., Dhamija, R., Di Capua, F., Dingfelder, J., Doležal, Z., Dong, T. V., Dorigo, M., Dossett, D., Dreyer, S., Dubey, S., Dujany, G., Ecker, P., Eliachevitch, M., Feichtinger, P., Ferber, T., Ferlewicz, D., Fillinger, T., Finocchiaro, G., Fodor, A., Forti, F., Frey, A., Fulsom, B. G., Gabrielli, A., Ganiev, E., Garcia-Hernandez, M., Gaudino, G., Gaur, V., Gaz, A., Gellrich, A., Ghevondyan, G.
Format:	Artikel
Sprache:	eng
Schlagworte:	Flavor symmetries Heavy mesons Lepton colliders Leptonic, semileptonic & radiative decays Particle data analysis Physics PHYSICS OF ELEMENTARY PARTICLES AND FIELDS Tau leptons
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Zusammenfassung:	We present the first measurement of the ratio of branching fractions of inclusive semileptonic $B$-meson decays, $R(X_{e/\mu}) = \mathcal{B}(B\to X \, e \, \nu) / \mathcal{B}(B\to X \, \mu \, \nu)$, a precision test of electron-muon universality, using data corresponding to $189\,\mathrm{fb}^{-1}$ from electron-positron collisions collected with the Belle II detector. In events where the partner $B$ meson is fully reconstructed, we use fits to the lepton momentum spectra above $1.3\,\mathrm{GeV}/c$ to obtain $R(X_{e/\mu}) = 1.007 \pm 0.009~(\mathrm{stat}) \pm 0.019~(\mathrm{syst})$, which is the most precise lepton-universality test of its kind and agrees with the standard-model expectation.
ISSN:	0031-9007 1079-7114
DOI:	10.1103/PhysRevLett.131.051804