Anomalous production of direct electrons in proton--proton interactions at 10, 15, and 24 GeV/c

Significant inclusive direct e+ production is found in proton-proton interactions at 10, 15 and 24 GeV/c and inclusive direct e- production at 24 GeV/c. The data were obtained at the Brookhaven National Laboratory Alternating Gradient Synchrotron. They were taken at theta/sub c.m./ near 900 and for a transverse momentum range 0.5 less than or equal to p/sub perpendicular/ less than or equal to 1.5 GeV/c. The e/π ratio was measured to be greater than or equal to 1 x 10-4 at all incident momenta, and in all cases exceeds the levels predicted from known sources for p/sub perpendicular/ to approximately less than 1 GeV/c. In addition, the ratio rises at low p perpendicular. At 15 GeV/c, the production of direct e+ appears independent of the incident particle, π+ or proton. No asymmetry was observed between the e+ and e- signals at 24 GeV/c; therefore, an electromagnetic source of the signals cannot be ruled out. Finally, the data are compared to levels expected from charmed particle and heavy lepton production and other possible sources are also discussed