Search for excited leptons in proton proton collisions at $\sqrt{s}$=8 TeV

We present a search for a possible compositeness of electrons and muons using a data sample of pp collisions at a center-of-mass energy of $\sqrt{s}$ = 8 TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb$^{-1}$. Excited leptons ($\ell^*$) are assumed to be produced via contact interactions in conjunction with a standard model lepton. The decays considered here are $\ell^* \to \ell \gamma$ and $\ell^* \to \ell Z$ which, depending on the Z decay mode, give final states with four leptons or two leptons and two jets. The Z boson is boosted, thus requiring dedicated reconstruction techniques; modified lepton isolation and a jet substructure technique are applied. The number of events observed in data is consistent with the expectation from the standard model and exclusion limits on the excited lepton mass, and the compositeness scale $\Lambda$, are set. For the case $M_{\ell^*} = \Lambda$ it is possible to exclude the existence of excited electrons (muons) up to masses of 2.45 (2.48) TeV.