Search for excited muons in $p \bar p $ collisions at $\sqrt s $ 1.96- TeV

We present the results of a search for the production of an excited state of the muon, μ + , in proton antiproton collisions at √s=1.96 TeV. The data have been collected with the D∅ experiment at the Fermilab Tevatron Collider and correspond to an integrated luminosity of approximately 380 pb -1 . We search for μ + in the process pp¯ →μ + μ, with the μ + subsequently decaying to a muon plus photon. No excess above the standard model expectation is observed in data. Interpreting our data in the context of a model that describes μ + production by four-fermion contact interactions and μ + decay via electroweak processes, we set a 95% confidence level production cross section upper limit ranging from 0.057 to 0.112 pb, depending on the mass of the excited muon. Choosing the scale for contact interactions to be Λ =1 TeV, excited muon masses below 618 GeV are excluded.