Limits on Anomalous Trilinear Gauge Couplings in Zgamma Events from ppbar Collisions at sqrt{s} = 1.96 TeV

TL;DR

This paper sets the most stringent limits to date on anomalous Z-gamma couplings using Tevatron collision data, finding results consistent with the Standard Model and indicating no evidence of new physics.

Contribution

It provides the first combined analysis of multiple decay channels to constrain Z-gamma couplings at Tevatron energies, improving previous limits significantly.

Findings

Limits on CP-conserving parameters: |h_3^{γ,Z}| < 0.022 and |h_4^{γ,Z}| < 0.0009

Results are consistent with Standard Model predictions

Most stringent limits on Z-gamma couplings to date

Abstract

Using \Zg\ candidate events collected by the CDF detector at the Tevatron Colli\der, we search for potential anomalous (non-standard-model) couplings between t\he $Z$ boson and the photon. \Zg\ couplings vanish at tree level and are heavil\y suppressed at higher orders; hence any evidence of couplings indicates new ph\ysics. Measurements are performed using data corresponding to an integrated lum\inosity of 4.9 \invfb\ in the $Z \rightarrow \nu\bar{\nu}$ decay channel and 5.\1 \invfb\ in the \Zll\ ($l=\mu, e$) decay channels. The combination of these me\asurements provides the most stringent limits to date on \Zg\ trilinear gauge c\ouplings. Using an energy scale of $\Lambda = 1.5$\ TeV to allow for a direct c\omparison with previous measurements, we find limits on the CP-conserving param\eters that describe \Zg\ couplings to be $|h_3^{\gamma,Z}| < 0.022 $ and $|h_4^\{\gamma,Z}| < 0.0009$. These results are consistent with standard model predict\ions.