Search for leptoquarks and other new particles with lepton-hadron signature in e⁺e^- interactions

Using the JADE detector at PETRA, a search for hadronic events with isolated leptons in e⁺e^- annihilation was performed. No evidence was found for the production of leptoquarks or color octet leptons and mass limits were obtained. Three hadronic events, each of them with two isolated muons, were detected and found to be in agreement with predictions of the α⁴ QED process {Mathematical expression}. At the highest PETRA energies, {Mathematical expression}, five events with low thrust, T<0.8, and a muon at a large angle with respect to the thrust axis, |cos δ|<0.7, were observed. The number of such events expected from an extrapolation of control data at lower energies is 0.56±0.18. No satisfactory explanation for the excess in terms of background could be found. A corresponding excess of electron events was not seen.