Zγ production and limits on anomalous ZZγ and Zγγ couplings in pp‾ collisions at √s=1.96 TeV

Abstract

We present a study of eeγ and μμγ events using 1109 (1009) pb^-1 of data in the electron (muon) channel, respectively. These data were collected with the DØ detector at the Fermilab Tevatron pp‾ collider at √s=1.96 TeV. Having observed 453 (515) candidates in the eeγ (μμγ) final state, we measure the Zγ production cross section for a photon with transverse energy ET> 7 GeV, separation between the photon and leptons ΔRlγ> 0.7, and invariant mass of the di-lepton pair Mll> 30 GeV/c², to be 4.96± 0.30(stat.+syst.)± 0.30(lumi.) pb, in agreement with the Standard Model prediction of 4.74± 0.22 pb. This is the most precise Zγ cross section measurement at a hadron collider. We set limits on anomalous trilinear Zγγ and ZZγ gauge boson couplings of -0.085< h^γ₃₀< 0.084,-0.0053< h^γ₄₀< 0.0054 and - 0.083 < h^Z₃₀ <0.082, -0.0053 < h^Z₄₀ < 0.0054 at the 95% C.L. for the form-factor scale Λ=1.2 TeV.