Single top production at HERA in the Standard Model and its minimal supersymmetric extension

The H1 Collaboration at the DESY electron-proton collider HERA has observed, in photoproduction and neutral-current deep-inelastic scattering, an unexpected excess of events with isolated leptons and missing transverse momentum, especially at large values of hadronic transverse momentum-a signature typical for single top-quark production. This observation is being substantiated in the HERA II run. Motivated by this, we evaluate the cross section of single top-quark photo- and electroproduction both in the Standard Model and its minimal supersymmetric extension, considering both minimal and non-minimal flavour-violation scenarios in the latter case.