Search for Excited Electrons in ep Collisions at HERA

TL;DR

This paper reports a comprehensive search for excited electrons in electron-proton collisions at HERA, setting new exclusion limits on their production and exploring contact interaction mechanisms for the first time.

Contribution

It provides the first analysis of excited electron production via contact interactions in ep collisions and extends exclusion limits beyond previous searches.

Findings

No evidence for excited electron production was observed.

New mass-dependent exclusion limits were established.

First investigation of contact interaction production mechanisms in ep collisions.

Abstract

A search for excited electrons is performed using the full $e^{\pm}p$ data sample collected by the H1 experiment at HERA, corresponding to a total luminosity of 475 pb$^{-1}$. The electroweak decays of excited electrons ${e}^{*}\to{e}{\gamma}$, ${e}^{*}\to{e}Z$ and ${e}^{*}{\to}\nu W$ with subsequent hadronic or leptonic decays of the $W$ and $Z$ bosons are considered. No evidence for excited electron production is found. Mass dependent exclusion limits on $e^*$ production cross sections and on the ratio $f/{\Lambda}$ of the coupling to the compositeness scale are derived within gauge mediated models. These limits extend the excluded region compared to previous excited electron searches. The $e^*$ production via contact interactions is also addressed for the first time in $ep$ collisions.