Searches for New Physics at HERA

Abstract

Recent results from searches for new physics at HERA are reviewed. Exploiting the uniqueness of lepton-hadron collisions at high energy, searches are performed for electron-quark resonant states (leptoquarks or squarks in R-parity-violating supersymmetry) or excited states of fermions. New phenomena at a very high energy scale, manifested at present energies as effective four-fermion contact interaction, are also investigated, including cases with lepton-flavor violation. Finally, the status of events with a high-energy lepton and missing transverse momentum is presented, resulting in the most stringent constraint on the flavor-changing neutral current t-u-γcoupling which could yield single-top production.

18 pages, 12 figures, to appear in the proceedings of "XV Rencontres de Physique de la Vallee d'Aoste", March 4-10, 2001, La Thuile, Italy. Text revised in Section 4