A search for an excited muon decaying to a muon and two jets in pp collisions at s = 8 TeV with the ATLAS detector atlas.publications@cern.ch

A new search signature for excited leptons is explored. Excited muons are sought in the channel pp → μ μ * → μ μ jet jet , assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb−1 of pp collision data at a centre-of-mass energy of s = 8 TeV taken with the ATLAS detector at the large hadron collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muon mass m μ * . For m μ * between 1.3 and 3.0 TeV, the upper limit on σ B ( μ * → μ q q ¯ ) is between 0.6 and 1 fb. Limits on σ B are converted to lower bounds on the compositeness scale Λ. In the limiting case Λ = m μ * , excited muons with a mass below 2.8 TeV are excluded. With the same model assumptions, these limits at larger μ * masses improve upon previous limits from traditional searches based on the gauge-mediated decay μ * → μ γ .