First observation of $Λ_c^+\rightarrowΛK^+π^0$ and evidence of $Λ_c^+\rightarrowΛK^+π^+π^-$
Creators: name: BESIII Collaboration
name: Ablikim, M.
name: Achasov, M. N.
name: Adlarson, P.
name: Ai, X. C.
name: Aliberti, R.
name: Amoroso, A.
name: An, M. R.
name: An, Q.
name: Bai, Y.
name: Bakina, O.
name: Balossino, I.
name: Ban, Y.
name: Bao, H. -R.
name: Batozskaya, V.
name: Begzsuren, K.
name: Berger, N.
name: Berlowski, M.
name: Bertani, M.
name: Bettoni, D.
name: Bianchi, F.
name: Bianco, E.
name: Bortone, A.
name: Boyko, I.
name: Briere, R. A.
name: Brueggemann, A.
name: Cai, H.
name: Cai, X.
name: Calcaterra, A.
name: Cao, G. F.
name: Cao, N.
name: Cetin, S. A.
name: Chang, J. F.
name: Chang, T. T.
name: Chang, W. L.
name: Che, G. R.
name: Chelkov, G.
name: Chen, C.
name: Chen, Chao
name: Chen, G.
name: Chen, H. S.
name: Chen, M. L.
name: Chen, S. J.
name: Chen, S. L.
name: Chen, S. M.
name: Chen, T.
name: Chen, X. R.
name: Chen, X. T.
name: Chen, Y. B.
name: Chen, Y. Q.
name: Chen, Z. J.
name: Choi, S. K.
name: Chu, X.
name: Cibinetto, G.
name: Coen, S. C.
name: Cossio, F.
name: Cui, J. J.
name: Dai, H. L.
name: Dai, J. P.
name: Dbeyssi, A.
name: de Boer, R. E.
name: Dedovich, D.
name: Deng, Z. Y.
name: Denig, A.
name: Denysenko, I.
name: Destefanis, M.
name: De Mori, F.
name: Ding, B.
name: Ding, X. X.
name: Ding, Y.
name: Ding, Y.
name: Dong, J.
name: Dong, L. Y.
name: Dong, M. Y.
name: Dong, X.
name: Du, M. C.
name: Du, S. X.
name: Duan, Z. H.
name: Egorov, P.
name: Fan, Y. H.
name: Fang, J.
name: Fang, S. S.
name: Fang, W. X.
name: Fang, Y.
name: Fang, Y. Q.
name: Farinelli, R.
name: Fava, L.
name: Feldbauer, F.
name: Felici, G.
name: Feng, C. Q.
name: Feng, J. H.
name: Fischer, K
name: Fritsch, M.
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name: Fu, Y. W.
name: Gao, H.
name: Gao, Y. N.
name: Gao, Yang
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name: Garzia, I.
name: Ge, P. T.
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name: Gersabeck, E. M.
name: Gilman, A
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name: Zhu, L.
name: Zhu, L. X.
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Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present the first observation of the singly Cabibbo-suppressed decay $Λ_c^+ \rightarrow ΛK^+π^0$ with a significance of $5.7σ$ and the first evidence of $Λ_c^+ \rightarrow ΛK^+π^+π^-$ decay with a significance of $3.1σ$, based on $e^+e^-$ annihilation data recorded by the BESIII detector at the BEPCII collider. The data correspond to an integrated luminosity of $6.4~{\rm fb^{-1}}$, in the center-of-mass energy range from $4.600~{\rm GeV}$ to $4.950~{\rm GeV}$. We determine the branching fractions of $Λ_c^+ \rightarrow ΛK^+π^0$ and $Λ_c^+ \rightarrow ΛK^+π^+π^-$ relative to their Cabibbo-favored counterparts to be $\frac{\mathcal{B}(Λ_c^+ \rightarrow ΛK^+π^0)}{\mathcal{B}(Λ_c^+ \rightarrow Λπ^+π^0)} = (2.09\pm0.39_{\mathrm{stat.}}\pm0.07_{\mathrm{syst.}}) \times 10^{-2}$ and $\frac{\mathcal{B}(Λ_c^+ \rightarrow ΛK^+π^+π^-)}{\mathcal{B}(Λ_c^+ \rightarrow Λπ^+π^+π^-)} = (1.13\pm0.41_{\mathrm{stat.}}\pm0.06_{\mathrm{syst.}}) \times 10^{-2}$, respectively. Moreover, by combining our measured result with the world average of $\mathcal{B}(Λ^+_c\to Λπ^+π^0)$, we obtain the branching fraction $\mathcal{B}(Λ_c^+ \to ΛK^+π^0) = (1.49\pm0.27_{\mathrm{stat.}}\pm0.05_{\mathrm{syst.}}\pm0.08_{\mathrm{ref.}}) \times 10^{-3}$. This result significantly departs from theoretical predictions based on quark $SU(3)$ flavor symmetry, which is underpinned by the presumption of meson pair $S$-wave amplitude dominance.