Observation of events at very high $Q^2$ in $e^+p$ collisions at HERA

Özet

Data collected at the $e^+p$ collider HERA at DESY by the experiments H1 and ZEUS have allowed to probe a previously inaccessible domain of very large $Q^2$ in deep-inelastic ep scattering. For $Q^2 > 15000 GeV^2$ both experiments see more events than expected assuming the Standard Model of deep-inelastic scattering. In this report the observed events, the theoretical expectations and their comparison are discussed.