Highly boosted dielectron identification in proton-proton collisions at √s = 13 TeV

A new technique is developed to identify dielectrons (e⁺e⁻) 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 e⁺e⁻ pairs are used to estimate the efficiency of the model with two tracks, yielding an overall efficiency of 80%. The Z → μ⁺μ⁻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/$ψ$K^± → e⁺e⁻K^± data.