Experimental Limit on Monojet Production in $e^+ e^-$ Annihilation

Abstract We have searched for monojet production in e + e − -annihilation with the CELLO detector operating at the highest PETRA energies. No events were found, which makes it unlikely that the recently observed monojets in p p collisions originate from unusual Z 0 decays. The upper limits on monojet cross sections are compared with various models, thus yielding upper limits on the production cross sections of Higgs bosons and higgsinos.