Search for free gluons in hadronic Z0 decays

A search was performed for isolated, neutral, highly energetic particles which interact hadronically with matter. The data sample consists of 134 278 multihadronic events observed by the OPAL detector at LEP in e+e− collisions with centre-of-mass energies around the Z0 pole. Our study is sensitive to events predicted by a model in which gluons appear as free, stable, particles. We observed two events and derive a lower limit at 95% confidence level of 47 GeV on the barrier height Vm of a potential well introduced by this model. A Monte Carlo simulation of standard multihadronic Z0 decays predicts 3.3 events.