OBSERVATION OF $p\bar{p}$, $p\bar{\Lambda}$, $K^-\bar{\Lambda}$ NEAR-THRESHOLD ENHANCEMENT AT BES

Abstract

We observe a narrow enhancement near 2mp in the invariant mass spectrum of [Formula: see text] pairs from radiative [Formula: see text] decays. In the case of S-wave fit, the peak mass is below 2mp at [Formula: see text] and the total width is Γ<30MeV at the 90% confidence level. And we also find near-threshold enhancement in the invariant mass spectrum of [Formula: see text] in [Formula: see text] decays. The mass is m=2075±12(stat)±5(syst)MeV and width is Γ=90±35(stat)±9(syst)MeV. A [Formula: see text] near-threshold enhancement is also studied and it has m=1.50~1.65GeV, Γ=70~110MeV with [Formula: see text].