Search for light leptoquark bosons

A search for light leptoquarks decaying into a lepton and a quark has been performed using the CELLO detector at the storage ring PETRA. Decay modes have been looked for where the lepton is either a muon or a neutrino, the latter being detected by a high missing transverse momentum. Except for one event previously reported no further two-jet events with two isolated muons were observed. No evidence for pair production of these particles has been found in other final states configurations. Our results are interpreted within a model where leptoquarks appear as a coloured Goldsone multiplet of charges 2/3.A 95% CL upper limit of 0.30 pb is set on the pair production cross section of such leptoquarks, thus excluding masses between 7 and 20.5 GeV.