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arXiv · 2207.11483

First Observation of the Semileptonic Decay $Λ_c^+\rightarrow pK^- e^+ν_e$

BESIII Collaboration·M. Ablikim·M. N. Achasov·P. Adlarson·M. Albrecht·R. Aliberti·A. Amoroso·M. R. An·Q. An·X. H. Bai·Y. Bai·O. Bakina·R. Baldini Ferroli·I. Balossino·Y. Ban·V. Batozskaya·D. Becker·K. Begzsuren·N. Berger·M. Bertani·D. Bettoni·F. Bianchi·J. Bloms·A. Bortone·I. Boyko·R. A. Briere·A. Brueggemann·H. Cai·X. Cai·A. Calcaterra·G. F. Cao·N. Cao·S. A. Cetin·J. F. Chang·W. L. Chang·G. Chelkov·C. Chen·Chao Chen·G. Chen·H. S. Chen·M. L. Chen·S. J. Chen·S. M. Chen·T. Chen·X. R. Chen·X. T. Chen·Y. B. Chen·Z. J. Chen·W. S. Cheng·S. K. Choi·X. Chu·G. Cibinetto·F. Cossio·J. J. Cui·H. L. Dai·J. P. Dai·A. Dbeyssi·R. E. de Boer·D. Dedovich·Z. Y. Deng·A. Denig·I. Denysenko·M. Destefanis·F. De Mori·Y. Ding·J. Dong·L. Y. Dong·M. Y. Dong·X. Dong·S. X. Du·P. Egorov·Y. L. Fan·J. Fang·S. S. Fang·W. X. Fang·Y. Fang·R. Farinelli·L. Fava·F. Feldbauer·G. Felici·C. Q. Feng·J. H. Feng·K Fischer·M. Fritsch·C. Fritzsch·C. D. Fu·H. Gao·Y. N. Gao·Yang Gao·S. Garbolino·I. Garzia·P. T. Ge·Z. W. Ge·C. Geng·E. M. Gersabeck·A Gilman·K. Goetzen·L. Gong·W. X. Gong·W. Gradl
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Abstract

Using $4.5~\mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data samples collected at the center-of-mass energies ranging from 4.600~GeV to 4.699~GeV with the BESIII detector at the BEPCII collider, a first study of the semileptonic decays $Λ_c^+\rightarrow pK^-e^+ν_e$, $Λ_c^+\rightarrow Λ(1520) e^+ν_e$ and $Λ_c^+\rightarrow Λ(1405) e^+ν_e$ is performed. The $Λ_c^+\rightarrow pK^-e^+ν_e$ decay is observed with a significance of $8.2σ$ and the branching fraction is measured to be $\mathcal{B}(Λ_c^+\rightarrow pK^- e^+ν_e)=(0.88\pm0.17_{\rm stat.}\pm0.07_{\rm syst.})\times 10^{-3}$. We also report evidence of $Λ_c^+\rightarrow Λ(1520)e^+ν_e$ and $Λ_c^+\rightarrow Λ(1405)e^+ν_e$ with significances of $3.3σ$ and $3.2σ$, respectively, and measure $\mathcal B(Λ^+_c\rightarrow Λ(1520)e^+ν_e)=(1.02\pm0.52_{\rm stat.}\pm0.11_{\rm syst.})\times10^{-3}$ and $\mathcal B(Λ^+_c\rightarrow Λ(1405)[\rightarrow pK^-]e^+ν_e)=(0.42\pm0.19_{\rm stat.}\pm0.04_{\rm syst.})\times10^{-3}$. Combining these with the inclusive semileptonic $Λ_c^+$ branching fraction measured by BESIII, the relative fraction is determined to be $[\mathcal{B}(Λ_c^+\rightarrow pK^-e^+ν_e)/\mathcal{B}(Λ_c^+\rightarrow X e^+ν_e)]=(2.1\pm0.4_{\rm stat.}\pm0.2_{\rm syst.})\%$, which provides a clear confirmation that semileptonic $Λ_c^+$ decays are not saturated by the $Λ\ell^+ν_{\ell}$ final state.

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BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, M. Albrecht, R. Aliberti, A. Amoroso, M. R. An, Q. An, X. H. Bai, Y. Bai, O. Bakina, R. Baldini Ferroli, I. Balossino, Y. Ban, V. Batozskaya, D. Becker, K. Begzsuren, N. Berger, M. Bertani, D. Bettoni, F. Bianchi, J. Bloms, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Cetin, J. F. Chang, W. L. Chang, G. Chelkov, C. Chen, Chao Chen, G. Chen, H. S. Chen, M. L. Chen, S. J. Chen, S. M. Chen, T. Chen, X. R. Chen, X. T. Chen, Y. B. Chen, Z. J. Chen, W. S. Cheng, S. K. Choi, X. Chu, G. Cibinetto, F. Cossio, J. J. Cui, H. L. Dai, J. P. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, Y. Ding, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, S. X. Du, P. Egorov, Y. L. Fan, J. Fang, S. S. Fang, W. X. Fang, Y. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, J. H. Feng, K Fischer, M. Fritsch, C. Fritzsch, C. D. Fu, H. Gao, Y. N. Gao, Yang Gao, S. Garbolino, I. Garzia, P. T. Ge, Z. W. Ge, C. Geng, E. M. Gersabeck, A Gilman, K. Goetzen, L. Gong, W. X. Gong, W. Gradl. 2022-12-28. First Observation of the Semileptonic Decay $Λ_c^+\rightarrow pK^- e^+ν_e$. https://doi.org/10.1103/physrevd.106.112010

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