Search for excited leptons decaying via contact interaction to two leptons and two jets

A search is presented for excited electrons and excited muons decaying via a contact interaction to final states of two leptons and two jets. This channel complements other searches for excited leptons with radiative or neutral current decays. In all cases, excited leptons would be produced via contact interaction with a characteristic energy scale $\Lambda$. The branching fraction of this decay channel increases with excited lepton mass and thus is expected to be the most sensitive search channel for very heavy excited leptons. The analysis uses proton-proton collision data collected in 2016 and 2017 with the CMS detector at the LHC at a center-of-mass energy of $13~\mathrm{TeV}$, corresponding to an integrated total luminosity of $77.4~\mathrm{fb}^{-1}$. The four-body invariant mass distribution is used as the discriminating variable for this search and no significant deviation from the standard model prediction is found. Exclusion limits are set at the $95\%$ confidence level. For the case where the characteristic scale is equal to the excited lepton mass, excited electrons and muons below $5.6~\mathrm{TeV}$ and $5.7~\mathrm{TeV}$, respectively, are excluded. These are the most stringent exclusion limits to date on the excited lepton mass.