M. Derrick et al., A SEARCH FOR EXCITED FERMIONS IN ELECTRON-PROTON COLLISIONS AT HERA, Zeitschrift fur Physik. C, Particles and fields, 65(4), 1995, pp. 627-647
A search for excited states of the standard model fermions was perform
ed using the ZEUS detector at the HERA electron-proton collider, opera
ting at a centre of mass energy of 296 GeV. In a sample corresponding
to an integrated luminosity of 0.55 pb(-1), no evidence was found for
any resonant state decaying into final states composed of a fermion an
d a gauge boson. Limits on the coupling strength times branching ratio
of excited fermions are presented for masses between 50 GeV and 250 G
eV, extending previous search regions significantly.