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arXiv · 2104.06224

Measurement of the branching fractions of $B\to\eta' K$ decays using 2019/2020 Belle II data

Belle II Collaboration·F. Abudinén·I. Adachi·R. Adak·K. Adamczyk·P. Ahlburg·J. K. Ahn·H. Aihara·N. Akopov·A. Aloisio·F. Ameli·L. Andricek·N. Anh Ky·D. M. Asner·H. Atmacan·V. Aulchenko·T. Aushev·V. Aushev·T. Aziz·V. Babu·S. Bacher·S. Baehr·S. Bahinipati·A. M. Bakich·P. Bambade·Sw. Banerjee·S. Bansal·M. Barrett·G. Batignani·J. Baudot·A. Beaulieu·J. Becker·P. K. Behera·M. Bender·J. V. Bennett·E. Bernieri·F. U. Bernlochner·M. Bertemes·E. Bertholet·M. Bessner·S. Bettarini·V. Bhardwaj·B. Bhuyan·F. Bianchi·T. Bilka·S. Bilokin·D. Biswas·A. Bobrov·A. Bondar·G. Bonvicini·A. Bozek·M. Bračko·P. Branchini·N. Braun·R. A. Briere·T. E. Browder·D. N. Brown·A. Budano·L. Burmistrov·S. Bussino·M. Campajola·L. Cao·G. Caria·G. Casarosa·C. Cecchi·D. Červenkov·M. C. Chang·P. Chang·R. Cheaib·V. Chekelian·C. Chen·Y. Q. Chen·Y. T. Chen·B. G. Cheon·K. Chilikin·K. Chirapatpimol·H. E. Cho·K. Cho·S. J. Cho·S. K. Choi·S. Choudhury·D. Cinabro·L. Corona·L. M. Cremaldi·D. Cuesta·S. Cunliffe·T. Czank·N. Dash·F. Dattola·E. De La Cruz-Burelo·G. de Marino·G. De Nardo·M. De Nuccio·G. De Pietro·R. de Sangro·B. Deschamps·M. Destefanis·S. Dey·A. De Yta-Hernandez·A. Di Canto
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Abstract

This note describes the rediscovery of $B\to\eta' K$ decays in Belle II data, both in the charged and neutral final state: $B_0\to\eta' K_S$ and $B^\pm\to\eta' K^\pm$. The $\eta'$ is searched for in two decay modes: $\eta'\to\eta\pi^+\pi^-$ with $\eta\to\gamma\gamma$, and $\eta'\to\rho\gamma$. The analysis uses data collected in 2019 and 2020 at the SuperKEKB asymmetric $e^+e^-$ collider, with an integrated luminosity of $62.8~fb^{-1}$, corresponding to $68.2$ million of $B\bar{B}$ pairs produced. The signal yield is obtained via an unbinned maximum likelihood fit to signal sensitive variables, obtaining branching ratios: $$\mathcal{B}\left(B^\pm\to\eta'K^\pm\right) = \left(63.4~^{+3.4}_{-3.3}\,(stat)\,\pm3.2\,(syst)\,\right) \times10^{-6} $$ $$\mathcal{B}\left(B_0\to\eta'K_S\right) = \left(59.9~^{+5.8}_{-5.5}\,(stat)\,\pm2.9\,(syst)\,\right) \times10^{-6} $$ which are consistent with world average.

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Belle II Collaboration, F. Abudinén, I. Adachi, R. Adak, K. Adamczyk, P. Ahlburg, J. K. Ahn, H. Aihara, N. Akopov, A. Aloisio, F. Ameli, L. Andricek, N. Anh Ky, D. M. Asner, H. Atmacan, V. Aulchenko, T. Aushev, V. Aushev, T. Aziz, V. Babu, S. Bacher, S. Baehr, S. Bahinipati, A. M. Bakich, P. Bambade, Sw. Banerjee, S. Bansal, M. Barrett, G. Batignani, J. Baudot, A. Beaulieu, J. Becker, P. K. Behera, M. Bender, J. V. Bennett, E. Bernieri, F. U. Bernlochner, M. Bertemes, E. Bertholet, M. Bessner, S. Bettarini, V. Bhardwaj, B. Bhuyan, F. Bianchi, T. Bilka, S. Bilokin, D. Biswas, A. Bobrov, A. Bondar, G. Bonvicini, A. Bozek, M. Bračko, P. Branchini, N. Braun, R. A. Briere, T. E. Browder, D. N. Brown, A. Budano, L. Burmistrov, S. Bussino, M. Campajola, L. Cao, G. Caria, G. Casarosa, C. Cecchi, D. Červenkov, M. C. Chang, P. Chang, R. Cheaib, V. Chekelian, C. Chen, Y. Q. Chen, Y. T. Chen, B. G. Cheon, K. Chilikin, K. Chirapatpimol, H. E. Cho, K. Cho, S. J. Cho, S. K. Choi, S. Choudhury, D. Cinabro, L. Corona, L. M. Cremaldi, D. Cuesta, S. Cunliffe, T. Czank, N. Dash, F. Dattola, E. De La Cruz-Burelo, G. de Marino, G. De Nardo, M. De Nuccio, G. De Pietro, R. de Sangro, B. Deschamps, M. Destefanis, S. Dey, A. De Yta-Hernandez, A. Di Canto. 2021-04-13. Measurement of the branching fractions of $B\to\eta' K$ decays using 2019/2020 Belle II data. https://arxiv.org/abs/2104.06224

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