Observation of the Singly Cabibbo-suppressed Decay Λ⁺<i>_c</i> → <i>p</i>π⁰

Utilizing 4.5 fb(-1) of e(+)e(-) annihilation data collected with the BESIII detector at the BEPCII collider at center-of-mass energies between 4.600 and 4.699 GeV, the first observation of the singly Cabibbo-suppressed decay Lambda(+)(c) -> p pi(0) is presented, with a statistical significance of 5.4 sigma. The ratio of the branching fractions of Lambda(+)(c) -> p pi(0) and Lambda(+)(c) -> p eta is measured as B(Lambda(+)(c) -> p pi(0))/B(Lambda(+)(c) -> p eta) = (0.120 +/- 0.026(stat) +/- 0.007(syst)). This result resolves the longstanding discrepancy between earlier experimental searches, providing both a decisive conclusion and valuable input for QCD-inspired theoretical models. A sophisticated deep learning approach using a Transformer-based architecture is employed to distinguish the signal from the prevalent hadronic backgrounds, complemented by thorough validation and systematic uncertainty quantification.