Measurement of the $ZZ\gamma$ and $Z\gamma\gamma$ Couplings in $p\bar p$ Collisions at $\sqrt{s} = 1.8$ TeV

TL;DR

This study measures the ZZ-gamma and Z-gamma-gamma couplings in proton-antiproton collisions at 1.8 TeV, setting limits on anomalous couplings through photon energy spectrum analysis with the D0 detector.

Contribution

First direct measurement of these couplings at Tevatron energies, providing new limits on anomalous couplings using photon energy spectra.

Findings

Set 95% CL limits on ZZ-gamma couplings.

Analyzed photon transverse energy spectrum.

Discussed limits on Z-gamma-gamma and CP-violating couplings.

Abstract

We have directly measured the ZZ-gamma and Z-gamma-gamma couplings by studying p pbar --> l+ l- gamma + X, (l = e, mu) events at the CM energy of 1.8$ TeV with the D0 detector at the Fermilab Tevatron Collider. A fit to the transverse energy spectrum of the photon in the signal events, based on the data set corresponding to an integrated luminosity of 13.9 pb^-1 ($13.3 pb^-1) for the electron (muon) channel, yields the following 95% confidence level limits on the anomalous CP-conserving ZZ-gamma couplings: -1.9 < h^Z_30 < 1.8 (h^Z_40 = 0), and -0.5 < h^Z_40 < 0.5 (h^Z_30 = 0), for a form-factor scale Lambda = 500 GeV. Limits for the Z-gamma-gamma$ couplings and CP-violating couplings are also discussed.