Observation of early photon conversions in high‐energy cosmic‐ray interactions

High energy cosmic ray interactions were studied by the JACEE Collaboration using balloon‐borne emulsion chambers at high altitude. In high energy, yet low multiplicity interactions many secondary vertices were observed, probably due to decays of short‐lived particles. Early conversions of photons were found in the vicinity of these vertices. Conversion distances and angular distributions of the photons were studied.