Observation of the decay Λc+→Σ−π+π+π0

We report the first observation of the decay Λc+→Σ−π+π+π0, based on data obtained in e+e− annihilations with an integrated luminosity of 567 pb−1 at s=4.6GeV. The data were collected with the BESIII detector at the BEPCII storage rings. The absolute branching fraction B(Λc+→Σ−π+π+π0) is determined to be (2.11±0.33(stat.)±0.14(syst.))%. In addition, an improved measurement of B(Λ+c→Σ−π+π+) is determined as (1.81±0.17(stat.)±0.09(syst.))%.