First observation of the decay Λc+ →n KS0 π+π0

Abstract

Based on 4.5 fb-1 of e+e- collision data accumulated at center-of-mass energies between 4599.53 and 4698.82 MeV with the BESIII detector, the decay Λc+→nKS0π+π0 is observed for the first time with a significance of 9.2σ. The branching fraction is measured to be (0.85±0.13±0.03)%, where the first uncertainty is statistical and the second is systematic, which differs from the theoretical prediction based on isospin by 4.4σ. This indicates that there may be resonant contributions or some unknown dynamics in this decay.