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arXiv · 2504.15881

Measurement of the time-integrated $CP$ asymmetry in $D^0 \to K^0_{\rm S} K^0_{\rm S}$ decays using opposite-side flavor tagging at Belle and Belle II

Belle·Belle II Collaborations·:·I. Adachi·Y. Ahn·N. Akopov·S. Alghamdi·M. Alhakami·A. Aloisio·N. Althubiti·K. Amos·M. Angelsmark·N. Anh Ky·C. Antonioli·D. M. Asner·H. Atmacan·T. Aushev·M. Aversano·R. Ayad·V. Babu·H. Bae·N. K. Baghel·S. Bahinipati·P. Bambade·Sw. Banerjee·M. Barrett·M. Bartl·J. Baudot·A. Baur·A. Beaubien·F. Becherer·J. Becker·J. V. Bennett·F. U. Bernlochner·V. Bertacchi·M. Bertemes·E. Bertholet·M. Bessner·S. Bettarini·B. Bhuyan·F. Bianchi·T. Bilka·D. Biswas·A. Bobrov·D. Bodrov·A. Bondar·J. Borah·A. Boschetti·A. Bozek·M. Bračko·P. Branchini·R. A. Briere·T. E. Browder·A. Budano·S. Bussino·M. Campajola·L. Cao·G. Casarosa·C. Cecchi·P. Cheema·B. G. Cheon·K. Chilikin·J. Chin·K. Chirapatpimol·H. -E. Cho·K. Cho·S. -J. Cho·S. -K. Choi·S. Choudhury·I. Consigny·L. Corona·J. X. Cui·E. De La Cruz-Burelo·S. A. De La Motte·G. de Marino·G. De Pietro·R. de Sangro·M. Destefanis·A. Di Canto·J. Dingfelder·Z. Doležal·I. Domínguez Jiménez·T. V. Dong·M. Dorigo·G. Dujany·P. Ecker·D. Epifanov·R. Farkas·P. Feichtinger·T. Ferber·T. Fillinger·C. Finck·G. Finocchiaro·A. Fodor·F. Forti·B. G. Fulsom·A. Gabrielli·A. Gale·E. Ganiev·M. Garcia-Hernandez
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Abstract

We measure the time-integrated $CP$ asymmetry in $D^0 \to K^0_{\rm S} K^0_{\rm S}$ decays reconstructed in $e^+e^-\to c{\overline c}$ events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 and 428 fb${}^{-1}$, respectively. To infer the flavor of the $D^0$ meson, we exploit the correlation between the flavor of the reconstructed decay and the electric charges of particles reconstructed in the rest of the $e^+e^-\to c{\overline c}$ event. This results in a sample which is independent from any other previously used at Belle or Belle II. The result, $A_{CP}(D^0 \to K^0_{\rm S} K^0_{\rm S}) = (1.3 \pm 2.0 \pm 0.2)\%$, where the first uncertainty is statistical and the second systematic, is consistent with previous determinations and with $CP$ symmetry.

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Belle, Belle II Collaborations, :, I. Adachi, Y. Ahn, N. Akopov, S. Alghamdi, M. Alhakami, A. Aloisio, N. Althubiti, K. Amos, M. Angelsmark, N. Anh Ky, C. Antonioli, D. M. Asner, H. Atmacan, T. Aushev, M. Aversano, R. Ayad, V. Babu, H. Bae, N. K. Baghel, S. Bahinipati, P. Bambade, Sw. Banerjee, M. Barrett, M. Bartl, J. Baudot, A. Baur, A. Beaubien, F. Becherer, J. Becker, J. V. Bennett, F. U. Bernlochner, V. Bertacchi, M. Bertemes, E. Bertholet, M. Bessner, S. Bettarini, B. Bhuyan, F. Bianchi, T. Bilka, D. Biswas, A. Bobrov, D. Bodrov, A. Bondar, J. Borah, A. Boschetti, A. Bozek, M. Bračko, P. Branchini, R. A. Briere, T. E. Browder, A. Budano, S. Bussino, M. Campajola, L. Cao, G. Casarosa, C. Cecchi, P. Cheema, B. G. Cheon, K. Chilikin, J. Chin, K. Chirapatpimol, H. -E. Cho, K. Cho, S. -J. Cho, S. -K. Choi, S. Choudhury, I. Consigny, L. Corona, J. X. Cui, E. De La Cruz-Burelo, S. A. De La Motte, G. de Marino, G. De Pietro, R. de Sangro, M. Destefanis, A. Di Canto, J. Dingfelder, Z. Doležal, I. Domínguez Jiménez, T. V. Dong, M. Dorigo, G. Dujany, P. Ecker, D. Epifanov, R. Farkas, P. Feichtinger, T. Ferber, T. Fillinger, C. Finck, G. Finocchiaro, A. Fodor, F. Forti, B. G. Fulsom, A. Gabrielli, A. Gale, E. Ganiev, M. Garcia-Hernandez. 2025-04-22. Measurement of the time-integrated $CP$ asymmetry in $D^0 \to K^0_{\rm S} K^0_{\rm S}$ decays using opposite-side flavor tagging at Belle and Belle II. https://doi.org/10.1103/8x1h-39dp

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