Searches for New Bosons Coupling to E-Q Pairs at HERA and Other Colliders

The early observation at HERA of an excess of events compared to theexpectation from the Standard Model in very short distance e^+pdeep-inelastic scattering processes has renewed the interest in the search fornew physics which could manifest in electroweak-like interactions. Newpreliminary results from the H1 and ZEUS experiments making use of allavailable e^+p data are reviewed here, with an emphasis on the search for newbosons possessing Yukawa couplings to lepton-quark pairs. The sensitivity ofHERA to leptoquarks, and to squarks of R-parity violating supersymmetry, isconfronted to existing indirect constraints from rare and forbiddensemi-leptonic decays, atomic parity violation and neutrinoless double-betadecay, as well as to direct constraints from LEP and Tevatron colliders. TheHERA and Tevatron colliders are found to offer exciting prospects for newphysics, accessing yet unexplored domains of the mass-coupling plane. Possiblestriking manifestation of explicit lepton flavour violation is also discussed.