Search for excited electrons and muons in ps = 8 TeV proton?proton collisions with the ATLAS detector

Abstract

The ATLAS detector at the Large Hadron Collider is used to search for excited electrons and excited muons in the channel pp → ``∗ → ``γ , assuming that excited leptons are produced via contact interactions. The analysis is based on 13 fb−1 of pp collisions at a centre-of-mass energy of 8 TeV. No evidence for excited leptons is found, and a limit is set at the 95% credibility level on the cross section times branching ratio as a function of the excitedlepton mass m` ∗ . For m` ∗ >0.8 TeV, the respective upper limits on σ B(`∗ → `γ ) are 0.75 and 0.90 fb for the e ∗ and µ ∗ searches. Limits on σ B are converted into lower bounds on the compositeness scale 3. In the special case where 3= m` ∗ , excited-electron and excited-muon masses below 2.2 TeV are excluded