Highly boosted dielectron identification in proton-proton collisions at sqrt(s) = 13 TeV

A new technique is developed to identify dielectrons (eþe−) with Lorentz boost γL > 20 that produce one single merged cluster in the electromagnetic calorimeter of the CMS detector. The identification uses two multivariate models: one for the case where both electron tracks are reconstructed, and another where only one of the tracks is reconstructed. The efficiency is determined using proton-proton collision data collected at a center-of-mass energy of 13 TeV. Boosted J=ψ mesons decaying into eþe− pairs are used to estimate the efficiency of the model with two tracks, yielding an overall efficiency of 80%. The Z → μþμ−γ events, where the photon converts into a collimated dielectron, are used for the model with a single track, yielding an efficiency of about 60%. A dedicated energy correction for dielectron candidates is also developed using B → J=ψK → eþe−K data.