A Search for Excited Fermions at HERA

TL;DR

This paper reports a search for excited first-generation fermions at HERA, analyzing various decay channels but finding no evidence, and setting limits on their production cross-sections and coupling constants.

Contribution

First comprehensive search for excited fermions at HERA considering all electroweak decay modes and final states, establishing new exclusion limits.

Findings

No evidence for excited fermions was observed.

Mass-dependent exclusion limits were set on production cross-sections.

Constraints on coupling constants relative to the compositeness scale were derived.

Abstract

A search for excited fermions f^* of the first generation in e^+p scattering at the collider HERA is presented using H1 data with an integrated luminosity of 37 pb^(-1). All electroweak decays of excited fermions, f^* -> f gamma, f W, f Z are considered and all possible final states resulting from the Z or W hadronic decays or decays into leptons of the first two generations are taken into account. No evidence for f^* production is found. Mass dependent exclusion limits on cross-sections and on the ratio of coupling constants to the compositeness scale are derived.