Measurement of Z gamma Production in pbar{p} Collisions at sqrt{s} = 1.96 TeV

TL;DR

This paper measures the production rate and kinematics of Z boson-associated photons in proton-antiproton collisions at 1.96 TeV, confirming standard model predictions and setting limits on anomalous couplings.

Contribution

First measurement of Z gamma production cross section at Tevatron energies, with limits on non-standard-model photon-Z couplings.

Findings

Measured cross section: 4.6 pb with uncertainties.

Photon transverse energy distribution used to set coupling limits.

Results consistent with standard model expectations.

Abstract

The production rate and kinematics of photons produced in association with Z bosons are studied using 2/fb of p\bar{p} collision data collected at the Collider Detector at Fermilab. The cross section for p\bar{p} -> l^+ l^- gamma + X (where the leptons l are either muons or electrons with dilepton mass M_{ll} > 40 GeV/c^2, and where the photon has transverse energy Et_{gamma} > 7 GeV and is well separated from the leptons) is 4.6 +/- 0.2 (stat) +/- 0.3 (syst) +/- 0.3 (lum) pb, which is consistent with standard model expectations. We use the photon Et distribution from Z-gamma events where the Z has decayed to mu^+ mu^-, e^+ e^-, or nu\bar{nu} to set limits on anomalous (non-standard-model) trilinear couplings between photons and Z bosons.