EXOTIC QUARK PRODUCTION AT DESY HERA ENERGIES

In this paper we present a study of the production and decay of exotic heavy quarks in the fermion-mirror-fermion, vector singlet, and vecto r doublet models. A Monte Carlo final-state reconstruction of events i s given for kinematical distributions. At energies reached at DESY HER A we show that exotic quarks in the mass range 100-150 GeV, and with m ixing angles of the order of sin(2) theta = 0.05, can be clearly domin ant over the standard ''top'' quark production. We discuss experimenta l cuts that can eliminate the ''bottom'' background. We compare the th eoretical predictions of the three models above in order to indicate a way to establish the origin of a possible experimental signal of an e xotic quark. Even if no such signal is found, HERA can still improve t he experimental bounds on exotic objects, although there is some model dependence on the estimates of total cross sections.