Abstract
A search for excited electrons is performed using the full e±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∗→eγ, e∗→eZ and e∗→νW 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/Λ 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.
Highlights
The three-family structure and mass hierarchy of the known fermions is one of the most puzzling characteristics of the Standard Model (SM) of particle physics
Using the full e±p data sample collected by the H1 experiment at HERA with an integrated luminosity of 475 pb−1 a search for the production of excited electrons is performed
An upper limit on the coupling f /Λ as a function of the excited electron mass is established for the specific relation f = +f between the couplings
Summary
The three-family structure and mass hierarchy of the known fermions is one of the most puzzling characteristics of the Standard Model (SM) of particle physics. Attractive explanations are provided by models assuming composite quarks and leptons [1]. The existence of excited states of leptons and quarks is a natural consequence of these models and their discovery would provide convincing evidence of a new scale of matter. Electron1-proton interactions at very high energies provide good conditions to search for excited states of first generation fermions. With a four-fold increase e+p collisions, in statistics, this of which 35 pb−1 were analysis supercedes the result of the previous H1 search for excited electrons [2]. It complements the search for excited neutrinos [3]
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