Excited fermions and other searches at HERA

Abstract

This paper reports a search in ep collisions for events with isolated τ leptons and large missing transverse momentum and for heavy excited fermions. The analysis of events with isolated τ followed the strategy used in the search for isolated electrons and muons. Two candidate events were found, while 0.12 ± 0.02 were expected from the Standard Model. The search for excited electrons and neutrinos led to direct constraints on the couplings and masses of these new states, which are the best ever reported for masses beyond 200 GeV.