Abstract:

Models of composite fermions are particularly attractive as a means of understanding the fermion generation structure observed in the Standard Model. The existence of excited states of the known fermions would be an unambiguous signal of compositeness. Excited fermions could be observed in direct searches. Their existence could also be inferred from deviations in the measurements of Standard Model processes from expectation. Both the direct searches and indirect constraints on excited leptons in e+e- collisions are reviewed. Results obtained using data collected by the OPAL detector at LEP are presented and compared with existing constraints from both low energy and other collider experiments. Future prospects of the search for compositeness are briefly summarised.