Evidence of the singly Cabibbo suppressed decay ${\Lambda }_{c}^{+}\to p{\pi }^{0}$

Evidence for the singly Cabibbo suppressed decay ${\Lambda }_{c}^{+}\to p{\pi }^{0}$ is reported for the first time with a statistical significance of $3.7\sigma $ based on $6.0\text{}\text{}{\mathrm{fb}}^{-1}$ of ${e}^{+}{e}^{-}$ collision data collected at center-of-mass energies between 4.600 and 4.843 GeV with the BESIII detector at the BEPCII collider. The absolute branching fraction of ${\Lambda }_{c}^{+}\to p{\pi }^{0}$ is measured to be $\left(1.5{6}_{-0.58}^{+0.72}±0.20\right)×{10}^{-4}$. Combining with the branching fraction of ${\Lambda }_{c}^{+}\to n{\pi }^{+}$, $\left(6.6±1.3\right)×{10}^{-4}$, the ratio of the branching fractions of ${\Lambda }_{c}^{+}\to n{\pi }^{+}$ and ${\Lambda }_{c}^{+}\to p{\pi }^{0}$ is calculated to be ${3.2}_{-1.2}^{+2.2}$. As an important input for the theoretical models describing the decay mechanisms of charmed baryons, our result indicates that the nonfactorizable contributions play an essential role and their interference with the factorizable contributions should not be significant. In addition, the absolute branching fraction of ${\Lambda }_{c}^{+}\to p\eta $ is measured to be $\left(1.63±0.3{1}_{\mathrm{stat}}±0.1{1}_{\mathrm{syst}}\right)×{10}^{-3}$.