First observation of ${\Lambda }_c^{+}\to \Lambda K^{+}{\pi }^0$ and evidence of ${\Lambda }_c^{+}\to \Lambda K^{+}{\pi }^{+}{\pi }^{-}$

Abstract

We present the first observation of the singly Cabibbo-suppressed decay ${\Lambda }_c^{+}\to \Lambda K^{+}{\pi }^0$ with a significance of $5.7\sigma$ and the first evidence of ${\Lambda }_c^{+}\to \Lambda K^{+}{\pi }^{+}{\pi }^{-}$ decay with a significance of $3.1\sigma$, based on $e^{+}{e}^{-}$ annihilation data recorded by the BESIII detector at the BEPCII collider. The data correspond to an integrated luminosity of $6.4\mathrm{f}{\mathrm{b}}^{-1}$, in the center-of-mass energy range from $4.600\mathrm{GeV}$ to $4.950\mathrm{GeV}$. We determine the branching fractions of ${\Lambda }_c^{+}\to \Lambda K^{+}{\pi }^0$ and ${\Lambda }_c^{+}\to \Lambda K^{+}{\pi }^{+}{\pi }^{-}$ relative to their Cabibbo-favored counterparts to be $\frac{\mathcal{B}({\Lambda }_c^{+}\to \Lambda K^{+}{\pi }^0)}{\mathcal{B}({\Lambda }_c^{+}\to \Lambda {\pi }^{+}{\pi }^0)}=(2.09\pm 0.39_{stat.}\pm 0.07_{syst.})\times 10^{-2}$ and $\frac{\mathcal{B}({\Lambda }_c^{+}\to \Lambda K^{+}{\pi }^{+}{\pi }^{-})}{\mathcal{B}({\Lambda }_c^{+}\to \Lambda {\pi }^{+}{\pi }^{+}{\pi }^{-})}=(1.13\pm 0.41_{stat.}\pm 0.06_{syst.})\times 10^{-2}$, respectively. Moreover, by combining our measured result with the world average of $\mathcal{B}({\Lambda }_c^{+}\to \Lambda {\pi }^{+}{\pi }^0)$, we obtain the branching fraction $\mathcal{B}({\Lambda }_c^{+}\to \Lambda K^{+}{\pi }^0)=(1.49\pm 0.27_{stat.}\pm 0.05_{syst.}\pm 0.08_{ref.})\times 10^{-3}$. 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.

References in corpus (10)

• Future Physics Programme of BESIII
• Method for detector description transformation to Unity and application in BESIII
• TopoAna: A generic tool for the event type analysis of inclusive Monte-Carlo samples in high energy physics experiments
• Luminosities and energies of $e^{+}{e}^{-}$ collision data taken between $\sqrt{s}$=4.612 GeV and 4.946 GeV at BESIII
• Study of the Standard Model with weak decays of charmed hadrons at BESIII
• Recent Progress in Leptonic and Semileptonic Decays of Charmed Hadrons
• Measurement of integrated luminosities at BESIII for data samples at center-of-mass energies between 4.0 and 4.6 GeV
• Measurement of the Energy-Dependent Electromagnetic Form Factors of a Charmed Baryon
• Observation of the Singly Cabibbo-Suppressed Decay ${\Lambda }_c^{+}\to n{\pi }^{+}$
• Measurement of the Branching Fraction of the Singly Cabibbo-Suppressed Decay ${\Lambda }_c^{+}\to \Lambda K^{+}$

Cited by in corpus (4)

• Nonleptonic three-body charmed baryon weak decays with H(15)
• Observation of ${\Lambda }_c^{+}\to \Lambda a_0(980{)}^{+}$ and Evidence for $\Sigma (1380{)}^{+}$ in ${\Lambda }_c^{+}\to \Lambda {\pi }^{+}\eta$
• Search for the low-lying excited baryon ${\Sigma }^{\ast }(1/2^{-})$ through process ${\Lambda }_c^{+}\to \Lambda K^0{\pi }^{+}$
• Search for the Cabibbo-suppressed decays ${\Lambda }_c^{+}\to {\Sigma }^0{K}^{+}{\pi }^0$ and ${\Lambda }_c^{+}\to {\Sigma }^0{K}^{+}{\pi }^{+}{\pi }^{-}$