Search for excited leptons at the HERA collider with the H1 detector

The work presented in this Ph.D. thesis is a search for first generation excited leptons using the full data sample collected by the Hl detector installed on the HERA electron (positron)-proton collider. This study is motivated by theoretical approaches which extend the Standard Model by assuming the existence of lepton compositeness. The whole e-p and e+p collisions data collected by Hi from 1994 to 2007 and corresponding to a total integrated luminosity of 475 pb-1 have been used for this analysis. The analysis of 13 different topologies was done, covering all the decay branching ratio of excited electrons (e*) and neutrinos (ν*). No evidence of the production of first generation excited leptons was observed. Exclusion limits on e* and ν* production cross section and on the coupling constant f/Λ as a function of the excited leptons mass are derived within gauge mediated models. The limit obtained extend the excluded region compared to previous excited lepton searches. For the first time at HERA, possible e* production via contact interactions is also studied. The e* production via contact and gauge productions together, including the interference between the two production modes, was considered. (author)