Excited Fermions at H1

TL;DR

This paper reports a search for excited neutrinos and electrons at HERA, setting new mass-dependent exclusion limits and finding no evidence of their production, thus extending the known exclusion region.

Contribution

It provides the first comprehensive search at HERA for excited fermions with the full dataset, establishing new exclusion limits at higher masses.

Findings

No evidence for excited fermions was observed.

New exclusion limits significantly extend previous bounds.

The limits depend on the ratio of coupling to compositeness scale.

Abstract

We present a search for excited neutrinos and electrons using all data collected by the H1 experiment at HERA at a center-of-mass energy of 320 GeV with an integrated luminosity of up to 435 pb$^{-1}$. No evidence for excited neutrino or electron production is found. Mass dependent exclusion limits are determined for the ratio of the coupling to the compositeness scale, $f/{\Lambda}$. These limits greatly extend the excluded region to higher masses than has been possible in previous searches.