Evidence of the singly Cabibbo suppressed decay Λc+ →pπ0

Evidence for the singly Cabibbo suppressed decay Λc+→pπ0 is reported for the first time with a statistical significance of 3.7σ based on 6.0 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 Λc+→pπ0 is measured to be (1.56-0.58+0.72±0.20)×10-4. Combining with the branching fraction of Λc+→nπ+, (6.6±1.3)×10-4, the ratio of the branching fractions of Λc+→nπ+ and Λc+→pπ0 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 Λc+→pη is measured to be (1.63±0.31stat±0.11syst)×10-3.