First Observation of the Semileptonic Decay ${\Lambda }_c^{+}\to p{K}^{-}{e}^{+}{\nu }_e$

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 ${\Lambda }_c^{+}\to p{K}^{-}{e}^{+}{\nu }_e$, ${\Lambda }_c^{+}\to \Lambda (1520)e^{+}{\nu }_e$ and ${\Lambda }_c^{+}\to \Lambda (1405)e^{+}{\nu }_e$ is performed. The ${\Lambda }_c^{+}\to p{K}^{-}{e}^{+}{\nu }_e$ decay is observed with a significance of $8.2\sigma$ and the branching fraction is measured to be $\mathcal{B}({\Lambda }_c^{+}\to p{K}^{-}{e}^{+}{\nu }_e)=(0.88\pm 0.17_{stat.}\pm 0.07_{syst.})\times 10^{-3}$. We also report evidence of ${\Lambda }_c^{+}\to \Lambda (1520)e^{+}{\nu }_e$ and ${\Lambda }_c^{+}\to \Lambda (1405)e^{+}{\nu }_e$ with significances of $3.3\sigma$ and $3.2\sigma$, respectively, and measure $\mathcal{B}({\Lambda }_c^{+}\to \Lambda (1520)e^{+}{\nu }_e)=(1.02\pm 0.52_{stat.}\pm 0.11_{syst.})\times 10^{-3}$ and $\mathcal{B}({\Lambda }_c^{+}\to \Lambda (1405)[\to p{K}^{-}]e^{+}{\nu }_e)=(0.42\pm 0.19_{stat.}\pm 0.04_{syst.})\times 10^{-3}$. Combining these with the inclusive semileptonic ${\Lambda }_c^{+}$ branching fraction measured by BESIII, the relative fraction is determined to be $[\mathcal{B}({\Lambda }_c^{+}\to p{K}^{-}{e}^{+}{\nu }_e)/\mathcal{B}({\Lambda }_c^{+}\to X{e}^{+}{\nu }_e)]=(2.1\pm 0.4_{stat.}\pm 0.2_{syst.})\%$, which provides a clear confirmation that semileptonic ${\Lambda }_c^{+}$ decays are not saturated by the $\Lambda {\ell }^{+}{\nu }_{\ell }$ final state.

13 pages, 9 figures and 2 tables

References in corpus (6)

• ${\Lambda }_c\to \Lambda {\ell }^{+}{\nu }_{\ell }$ form factors and decay rates from lattice QCD with physical quark masses
• Luminosities and energies of $e^{+}{e}^{-}$ collision data taken between $\sqrt{s}$=4.612 GeV and 4.946 GeV at BESIII
• Predictions for the ${\Lambda }_b\to J/\psi \Lambda (1405)$ decay
• Measurement of the Absolute Branching Fraction for ${\Lambda }_c^{+}\to \Lambda {\mu }^{+}{\nu }_{\mu }$
• Lambda_b -> Lambda l+ l- form factors and differential branching fraction from lattice QCD
• ${\Lambda }_c$ Semileptonic Decays in a Quark Model

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• Charm Physics at the Super $\tau$-Charm Factory
• A novel method for searching the ${\Xi }_c^{0/+}$-${\Xi }_c^{\prime 0/+}$ mixing effect in the angular distribution analysis of a four-body ${\Xi }_c^{0/+}$ decay
• Improved measurement of the absolute branching fraction of inclusive semileptonic ${\Lambda }_c^{+}$ decay
• Baryons and baryoniums in the perspective of QCD sum rules
• Evidence for the semileptonic decays ${\Lambda }_c^{+}\to {\Sigma }^{\pm }{\pi }^{\mp }{e}^{+}{\nu }_e$