A search for excited leptons in pp Collisions at sqrt(s) = 7 TeV

TL;DR

This paper reports a search for excited leptons in proton-proton collisions at 7 TeV using CMS data, setting new limits on their production and excluding masses below about 1 TeV for certain model parameters.

Contribution

It provides the first upper limits on excited lepton production at 7 TeV and extends the exclusion region in the parameter space beyond previous results.

Findings

No excess events observed above standard model expectations.

Excluded excited lepton masses below 1070 GeV/c^2 for electrons.

Excluded excited lepton masses below 1090 GeV/c^2 for muons.

Abstract

A search for excited leptons is carried out with the CMS detector at the LHC, using 36 inverse picobarns of pp collision data recorded at sqrt(s) = 7 TeV. The search is performed for associated production of a lepton and an oppositely charged excited lepton pp to l l*, followed by the decay l* to l gamma, resulting in the l l gamma final state, where l = electron or muon. No excess of events above the standard model expectation is observed. Interpreting the findings in the context of l* production through four-fermion contact interactions and subsequent decay via electroweak processes, first upper limits are reported for l* production at this collision energy. The exclusion region in the compositeness scale Lambda and excited lepton mass M(l*) parameter space is extended beyond previously established limits. For Lambda = M(l*), excited lepton masses are excluded below 1070 GeV/c^2 for e* and 1090 GeV/c^2 for mu* at the 95% confidence level.