  A search for compositeness of electrons and muons is presented using a data
sample of proton-proton 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 inverse femtobarns. Excited leptons (l*) produced
via contact interactions in conjunction with a standard model lepton are
considered, and a search is made for their gauge decay modes. The decays
considered are l* to l + gamma and l* to l + Z, which give final states of two
leptons and a photon or, depending on the Z-boson decay mode, four leptons or
two leptons and two jets. The number of events observed in data is consistent
with the standard model prediction. Exclusion limits are set on the excited
lepton mass, and the compositeness scale Lambda. For the case M(l*) = Lambda
the existence of excited electrons (muons) is excluded up to masses of 2.45
(2.47) TeV at 95% confidence level. Neutral current decays of excited leptons
are considered for the first time, and limits are extended to include the
possibility that the weight factors f and f', which determine the couplings
between standard model leptons and excited leptons via gauge mediated
interactions, have opposite sign.
