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arXiv · 2104.12624

Search for $B^{+}\to K^{+}\nu\bar{\nu}$ decays using an inclusive tagging method at Belle II

Belle II Collaboration·F. Abudinén·I. Adachi·K. Adamczyk·P. Ahlburg·H. Aihara·N. Akopov·A. Aloisio·N. Anh Ky·D. M. Asner·H. Atmacan·T. Aushev·V. Aushev·A. Baur·V. Babu·S. Baehr·P. Bambade·Sw. Banerjee·S. Bansal·J. Baudot·J. Becker·P. K. Behera·J. V. Bennett·E. Bernieri·F. U. Bernlochner·M. Bertemes·E. Bertholet·M. Bessner·S. Bettarini·F. Bianchi·T. Bilka·D. Biswas·A. Bozek·M. Bračko·P. Branchini·N. Braun·T. E. Browder·A. Budano·S. Bussino·M. Campajola·L. Cao·G. Casarosa·C. Cecchi·D. Červenkov·P. Chang·R. Cheaib·V. Chekelian·C. Chen·Y. -T. Chen·B. G. Cheon·K. Chilikin·K. Chirapatpimol·K. Cho·S. -J. Cho·S. Choudhury·D. Cinabro·L. Corona·L. M. Cremaldi·S. Cunliffe·T. Czank·F. Dattola·E. De La Cruz-Burelo·G. de Marino·G. De Nardo·M. De Nuccio·G. De Pietro·R. de Sangro·M. Destefanis·S. Dey·A. De Yta-Hernandez·A. Di Canto·F. Di Capua·J. Dingfelder·Z. Doležal·I. Domínguez Jiménez·T. V. Dong·K. Dort·S. Dubey·S. Duell·G. Dujany·S. Eidelman·M. Eliachevitch·D. Epifanov·T. Ferber·D. Ferlewicz·T. Fillinger·G. Finocchiaro·S. Fiore·A. Fodor·F. Forti·A. Frey·B. G. Fulsom·N. Gabyshev·E. Ganiev·M. Garcia-Hernandez·A. Garmash·V. Gaur·A. Gaz·A. Gellrich·R. Giordano
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Abstract

A search for the flavor-changing neutral-current decay $B^{+}\to K^{+}\nu\bar{\nu}$ is performed at the Belle II experiment at the SuperKEKB asymmetric energy electron-positron collider. The results are based on a data sample corresponding to an integrated luminosity of $63\,\mbox{fb}^{-1}$ collected at the $\Upsilon{(4S)}$ resonance and a sample of $9\,\mbox{fb}^{-1}$ collected at an energy $60\mathrm{\,Me\kern -0.1em V}$ below the resonance. A novel measurement method is employed, which exploits topological properties of the $B^{+}\to K^{+}\nu\bar{\nu}$ decay that differ from both generic bottom-meson decays and light-quark pair production. This inclusive tagging approach offers a higher signal efficiency compared to previous searches. No significant signal is observed. An upper limit on the branching fraction of $B^{+}\to K^{+}\nu\bar{\nu}$ of $4.1 \times 10^{-5}$ is set at the 90% confidence level.

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Belle II Collaboration, F. Abudinén, I. Adachi, K. Adamczyk, P. Ahlburg, H. Aihara, N. Akopov, A. Aloisio, N. Anh Ky, D. M. Asner, H. Atmacan, T. Aushev, V. Aushev, A. Baur, V. Babu, S. Baehr, P. Bambade, Sw. Banerjee, S. Bansal, J. Baudot, J. Becker, P. K. Behera, J. V. Bennett, E. Bernieri, F. U. Bernlochner, M. Bertemes, E. Bertholet, M. Bessner, S. Bettarini, F. Bianchi, T. Bilka, D. Biswas, A. Bozek, M. Bračko, P. Branchini, N. Braun, T. E. Browder, A. Budano, S. Bussino, M. Campajola, L. Cao, G. Casarosa, C. Cecchi, D. Červenkov, P. Chang, R. Cheaib, V. Chekelian, C. Chen, Y. -T. Chen, B. G. Cheon, K. Chilikin, K. Chirapatpimol, K. Cho, S. -J. Cho, S. Choudhury, D. Cinabro, L. Corona, L. M. Cremaldi, S. Cunliffe, T. Czank, F. Dattola, E. De La Cruz-Burelo, G. de Marino, G. De Nardo, M. De Nuccio, G. De Pietro, R. de Sangro, M. Destefanis, S. Dey, A. De Yta-Hernandez, A. Di Canto, F. Di Capua, J. Dingfelder, Z. Doležal, I. Domínguez Jiménez, T. V. Dong, K. Dort, S. Dubey, S. Duell, G. Dujany, S. Eidelman, M. Eliachevitch, D. Epifanov, T. Ferber, D. Ferlewicz, T. Fillinger, G. Finocchiaro, S. Fiore, A. Fodor, F. Forti, A. Frey, B. G. Fulsom, N. Gabyshev, E. Ganiev, M. Garcia-Hernandez, A. Garmash, V. Gaur, A. Gaz, A. Gellrich, R. Giordano. 2021-04-26. Search for $B^{+}\to K^{+}\nu\bar{\nu}$ decays using an inclusive tagging method at Belle II. https://doi.org/10.1103/physrevlett.127.181802

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