First observation of Λ_c(2595)⁺ → Λ_c⁺ π⁰π⁰ and Λ_c(2625)⁺ → Λ_c⁺ π⁰ π⁰

By analysing e +e − annihilation data corresponding to an integrated luminosity of 368.48 pb−1 collected at the centre-of-mass energies of √ s = 4.918 and 4.951 GeV with the BESIII detector, we report the first observation of Λc(2595)+ and Λc(2625)+ → Λ + c π 0π 0 with statistical significances of 7.9σ and 11.8σ, respectively. The branching fractions of Λc(2595)+ and Λc(2625)+ → Λ + c π 0π 0 are measured to be (59.5 ± 11.1stat. ± 7.9syst.)% and (41.0 ± 5.2stat. ± 3.3syst.)%, respectively. The absolute branching fraction of Λc(2595)+ is consistent with the expectation of the mechanism referred to as the threshold effect, proposed for the strong decays of Λc(2595)+ within uncertainty.