arXiv · 2610.31377
Measurements of the branching fractions of $Λ_c^+\toΛK^+ π^0$ and $Λ_c^+\toΛK^+ η$ decays at Belle and Belle II
Abstract
We present a study of the three-body, singly Cabibbo-suppressed decays $Λ_c^+ \to ΛK^+ π^0$ and $Λ_c^+ \to ΛK^+ η$ using data recorded with the Belle and Belle II detectors at the KEKB and SuperKEKB $e^+ e^-$ colliders. The data samples correspond to integrated luminosities of 980$\,\mathrm{fb}^{-1}$ and 570$\,\mathrm{fb}^{-1}$, respectively. We measure their branching-fraction ratios relative to the Cabibbo-favored decay $Λ_c^+ \to Λπ^+ π^0$ as $\mathcal{B}(Λ_c^+ \to ΛK^+ π^0)/\mathcal{B}(Λ_c^+ \to Λπ^+ π^0)=(1.82 \pm 0.07 \pm 0.07)\%$, with significantly improved precision compared to the previous measurement, and $\mathcal{B}(Λ_c^+ \to ΛK^+ η)/\mathcal{B}(Λ_c^+ \to Λπ^+ π^0)=(8.73 \pm 0.35 \pm 0.43)\times10^{-3}$, corresponding to the first observation of the $Λ_c^+ \to ΛK^+ η$ decay with a statistical significance exceeding 10 standard deviations. The first and second uncertainties are statistical and systematic, respectively. Using the world-average value of the branching fraction for $Λ_c^+ \to Λπ^+ π^0$, we obtain the branching fractions $\mathcal{B}(Λ_c^+ \to ΛK^+ π^0)=(1.29\pm 0.05\pm 0.05\pm 0.06)\times10^{-3}$ and $\mathcal{B}(Λ_c^+ \to ΛK^+ η)=(6.20\pm 0.25\pm 0.31\pm 0.30)\times10^{-4}$, where the third uncertainty arises from the uncertainty in the world-average value of $\mathcal{B}(Λ_c^+ \to Λπ^+ π^0)$. The measured $\mathcal{B}(Λ_c^+\toΛK^+η)$ is significantly larger than predictions based on $SU(3)$ flavor symmetry.
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Belle, Belle II Collaborations, :, M. Abumusabh, I. Adachi, A. Aggarwal, Y. Ahn, H. Aihara, M. Akdag, N. Akopov, A. Akram, S. Alghamdi, M. Alhakami, A. Aloisio, N. Althubiti, K. Amos, M. Angelsmark, N. Anh Ky, K. Arai, H. Atmacan, T. Aushev, V. Aushev, R. Ayad, V. Babu, N. K. Baghel, S. Bahinipati, P. Bambade, Sw. Banerjee, M. Barrett, M. Bartl, J. Baudot, A. Beaubien, F. Becherer, J. Becker, G. F. Benfratello, J. V. Bennett, V. Bertacchi, M. Bertemes, E. Bertholet, M. Bessner, S. Bettarini, P. Bhagawath Prasad, V. Bhardwaj, B. Bhuyan, F. Bianchi, T. Bilka, A. Biswas, A. Bobrov, A. Bondar, G. Bonvicini, A. Boschetti, A. Bozek, M. Bračko, P. Branchini, N. Brenny, R. A. Briere, T. E. Browder, A. Budano, F. Callet, Q. Campagna, M. Campajola, M. Carminati, G. Casarosa, C. Cecchi, P. Cheema, C. Chen, L. Chen, B. G. Cheon, C. Cheshta, H. Chetri, K. Chilikin, K. Chirapatpimol, H. -E. Cho, K. Cho, S. -K. Choi, S. Choudhury, S. Chutia, J. Cochran, J. A. Colorado-Caicedo, I. Consigny, L. Corona, S. Cuccuini, J. X. Cui, L. Damer, S. Das, S. A. De La Motte, G. De Nardo, G. De Pietro, R. de Sangro, M. Destefanis, S. Dey, R. Dhayal, A. Di Canto, J. Dingfelder, Z. Doležal, I. Dom\'ınguez Jiménez, X. Dong, M. Dorigo, M. Dort, G. Dujany. 2026-10-22. Measurements of the branching fractions of $Λ_c^+\toΛK^+ π^0$ and $Λ_c^+\toΛK^+ η$ decays at Belle and Belle II. https://arxiv.org/abs/2610.31377
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