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arXiv · 2509.25765

Search for $CP$ violation in $\Xi_c^+\to\Sigma^+h^+h^-$ and $\Lambda_c^+\to ph^+h^-$ at Belle II

Belle II Collaboration·M. Abumusabh·I. Adachi·H. Ahmed·Y. Ahn·H. Aihara·N. Akopov·S. Alghamdi·M. Alhakami·N. Althubiti·K. Amos·N. Anh Ky·D. M. Asner·H. Atmacan·R. Ayad·V. Babu·N. K. Baghel·S. Bahinipati·P. Bambade·Sw. Banerjee·M. Bartl·J. Baudot·A. Beaubien·J. Becker·J. V. Bennett·V. Bertacchi·M. Bertemes·E. Bertholet·S. Bettarini·V. Bhardwaj·D. Biswas·A. Bobrov·D. Bodrov·G. Bonvicini·J. Borah·A. Boschetti·M. Bračko·P. Branchini·R. A. Briere·T. E. Browder·A. Budano·S. Bussino·Q. Campagna·M. Campajola·G. Casarosa·C. Cecchi·P. Chang·P. Cheema·L. Chen·B. G. Cheon·C. Cheshta·H. Chetri·K. Chilikin·J. Chin·K. Chirapatpimol·H. -E. Cho·K. Cho·S. -J. Cho·S. -K. Choi·S. Choudhury·S. Chutia·J. A. Colorado-Caicedo·I. Consigny·L. Corona·J. X. Cui·S. Das·S. A. De La Motte·G. De Nardo·G. De Pietro·R. de Sangro·M. Destefanis·A. Di Canto·Z. Doležal·I. Domínguez Jiménez·T. V. Dong·X. Dong·M. Dorigo·G. Dujany·P. Ecker·D. Epifanov·J. Eppelt·R. Farkas·P. Feichtinger·T. Ferber·T. Fillinger·G. Finocchiaro·F. Forti·B. G. Fulsom·A. Gabrielli·E. Ganiev·R. Garg·G. Gaudino·V. Gaur·V. Gautam·A. Gaz·A. Gellrich·D. Ghosh·H. Ghumaryan·R. Giordano·A. Giri
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Abstract

We report decay-rate $CP$ asymmetries of the singly-Cabibbo-suppressed decays $\Xi_c^+\to\Sigma^+h^+h^-$ and $\Lambda_c^+\to ph^+h^-$, with $h=K,\pi$, measured using 428 fb$^{-1}$ of $e^+e^-$ collisions collected by the Belle II experiment at the SuperKEKB collider. The results, \begin{equation} A_{CP}(\Xi_c^+\to\Sigma^+K^+K^-) = (3.7\pm6.6\pm0.6)\%, \end{equation} \begin{equation} A_{CP}(\Xi_c^+\to\Sigma^+\pi^+\pi^-) = (9.5\pm6.8\pm0.5)\%, \end{equation} \begin{equation} A_{CP}(\Lambda_c^+\to pK^+K^-) = (3.9\pm1.7\pm0.7)\%, \end{equation} \begin{equation} A_{CP}(\Lambda_c^+\to p\pi^+\pi^-) = (0.3\pm1.0\pm0.2)\%, \end{equation} where the first uncertainties are statistical and the second systematic, agree with $CP$ symmetry. From these results we derive the sums \begin{equation} A_{CP}(\Xi_c^+\to\Sigma^+\pi^+\pi^-) \, + \, A_{CP}(\Lambda_c^+\to pK^+K^-) = (13.4 \pm 7.0\pm 0.9)\%, \end{equation} \begin{equation} A_{CP}(\Xi_c^+\to\Sigma^+K^+K^-) \, + \, A_{CP}(\Lambda_c^+\to p\pi^+\pi^-) = (\phantom{0}4.0 \pm 6.6\pm 0.7)\%, \end{equation} which are consistent with the $U$-spin symmetry prediction of zero. These are the first measurements of $CP$ asymmetries for individual hadronic three-body charmed-baryon decays.

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Belle II Collaboration, M. Abumusabh, I. Adachi, H. Ahmed, Y. Ahn, H. Aihara, N. Akopov, S. Alghamdi, M. Alhakami, N. Althubiti, K. Amos, N. Anh Ky, D. M. Asner, H. Atmacan, R. Ayad, V. Babu, N. K. Baghel, S. Bahinipati, P. Bambade, Sw. Banerjee, M. Bartl, J. Baudot, A. Beaubien, J. Becker, J. V. Bennett, V. Bertacchi, M. Bertemes, E. Bertholet, S. Bettarini, V. Bhardwaj, D. Biswas, A. Bobrov, D. Bodrov, G. Bonvicini, J. Borah, A. Boschetti, M. Bračko, P. Branchini, R. A. Briere, T. E. Browder, A. Budano, S. Bussino, Q. Campagna, M. Campajola, G. Casarosa, C. Cecchi, P. Chang, P. Cheema, L. Chen, B. G. Cheon, C. Cheshta, H. Chetri, K. Chilikin, J. Chin, K. Chirapatpimol, H. -E. Cho, K. Cho, S. -J. Cho, S. -K. Choi, S. Choudhury, S. Chutia, J. A. Colorado-Caicedo, I. Consigny, L. Corona, J. X. Cui, S. Das, S. A. De La Motte, G. De Nardo, G. De Pietro, R. de Sangro, M. Destefanis, A. Di Canto, Z. Doležal, I. Domínguez Jiménez, T. V. Dong, X. Dong, M. Dorigo, G. Dujany, P. Ecker, D. Epifanov, J. Eppelt, R. Farkas, P. Feichtinger, T. Ferber, T. Fillinger, G. Finocchiaro, F. Forti, B. G. Fulsom, A. Gabrielli, E. Ganiev, R. Garg, G. Gaudino, V. Gaur, V. Gautam, A. Gaz, A. Gellrich, D. Ghosh, H. Ghumaryan, R. Giordano, A. Giri. 2025-09-30. Search for $CP$ violation in $\Xi_c^+\to\Sigma^+h^+h^-$ and $\Lambda_c^+\to ph^+h^-$ at Belle II. https://doi.org/10.1103/s2gy-c3vh

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