Evidence for the semileptonic decay ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^{-}{e}^{+}{\nu }_e$

Based on $4.5{\mathrm{f}\mathrm{b}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected with the BESIII detector at the BEPCII collider at center-of-mass energies between $4.600\mathrm{G}\mathrm{e}\mathrm{V}$ and $4.699\mathrm{G}\mathrm{e}\mathrm{V}$, the first search for the Cabbibo-suppressed semileptonic decay ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^{-}{e}^{+}{\nu }_e$ is performed. The branching fraction of ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^{-}{e}^{+}{\nu }_e$ is measured to be $(2.96\pm {0.95}_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}}\pm {0.23}_{\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}})\times {10}^{-4}$ with a signal significance of $4.2\sigma$.