Direct production of electrons in 70 GeV/c π− p interactions

In a search for directly produced electrons from 64 000 π− p interactions at 70 GeV/c using the Big European Bubble Chamber equipped with a track sensitive target, we find 5 events with only one electron (positron). In addition there are 12 events in which an e+e− pair was formed with an invariant mass greater than 135 MeV. Backgrounds to both of these processes are small. The e±/π± ratio for the single electrons is found to be (3.1 ± 1.7) × 10−5. If the direct electrons are assumed to be products of charmed particle decay, we calculate the production cross section for pairs of charmed particles to be 19 ± 11 μb. We further find that the e±/π± ratio from e+e− pairs (greater than 135 MeV) is (0.88 ± 0.26) × 10−4.