Production of prompt electrons in the charm Pt‐region at √s=630 GeV

The production of prompt electrons at √s=630 GeV has been measured in the pt range 0.5–2.0 GeV/c using a Ring Imaging CHerenkov (RICH) counter installed in the UA2 experiment at the CERN pp collider. From our measurement of the electron/hadron ratio in the pt range 0.9–1.5 GeV/c we conclude that the charm production cross‐section does not exceed 1.9 mb at 95% CL. As best estimate we obtain σ(cc)=684±557(stat)±253(sys,exp)±205(sys,theory) μb. The RICH counter was operated successfully at the collider providing an electron/pion separation capability of better than 8–10−5 at momenta below the pion threshold.