Zgamma production and limits on anomalous ZZgamma and Zgammagamma couplings in ppbar collisions at sqrt(s) = 1.96 TeV

TL;DR

This paper measures the Zgamma production cross section in proton-antiproton collisions at 1.96 TeV, and sets limits on anomalous gauge boson couplings, providing the most precise measurement at a hadron collider.

Contribution

It provides the most precise measurement of Zgamma production cross section and sets new limits on anomalous ZZgamma and Zgammagamma couplings at a hadron collider.

Findings

Measured Zgamma cross section as 4.96 pb, consistent with the Standard Model.

Set limits on anomalous couplings at 95% confidence level.

Achieved the most precise Zgamma cross section measurement at a hadron collider.

Abstract

We present a study of eegamma and mumugamma events using 1109 (1009) pb-1 of data in the electron (muon) channel, respectively. These data were collected with the D0 detector at the Fermilab Tevatron ppbar Collider at sqrt(s) = 1.96 TeV. Having observed 453 (515) candidates in the eegamma (mumugamma) final state, we measure the Zgamma production cross section for a photon with transverse energy ET > 7 GeV, separation between the photon and leptons Delta R(lgamma) > 0.7, and invariant mass of the di-lepton pair M(ll) > 30 GeV/c^2, 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 Zgamma cross section measurement at a hadron collider. We set limits on anomalous trilinear Zgammagamma and ZZgamma gauge boson couplings of -0.085 < h(30)^(gamma) < 0.084, -0.0053 < h(40)^(gamma) < 0.0054 and -0.083 < h(30)^(Z) < 0.082, -0.0053 < h(40)^(Z) < 0.0054 at the 95% C.L. for the form-factor scale Lambda = 1.2 TeV.