Observation of a direct low-mass e+e− continuum in π-p interactions at 16 GeV/c☆

Abstract The production of prompt electron-positron pairs in 16 GeV/ c π - p collisions has been measured using the LASS spectrometer at SLAC. An excess of events is observed above the estimated contribution of direct and Dalitz decays of known resonances in the kinematic range defined by 0.1⩽χ⩽0.45, 0⩽p T ⩽0.8 GeV c and 0.2⩽M(e + e − )⩽0.7 GeV c 2 . The excess signal decreases slowly with increasing M , but exhibits very steep χ and p T 2 dependence.