Observation of WZ Production

TL;DR

This paper reports the first observation of WZ boson pair production in proton-antiproton collisions, confirming a key Standard Model prediction with high statistical significance.

Contribution

First experimental observation of WZ production at the Tevatron, providing important validation of the Standard Model predictions.

Findings

Observed 16 WZ candidates with low background

Significance of six standard deviations for the excess

Measured cross section consistent with Standard Model

Abstract

We report the first observation of the associated production of a W boson and a Z boson. This result is based on 1.1 fb-1 of integrated luminosity from ppbar collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. We observe 16 WZ candidates passing our event selection with an expected background of 2.7 +/- 0.4 events. A fit to the missing transverse energy distribution indicates an excess of events compared to the background expectation corresponding to a significance equivalent to six standard deviations. The measured cross section is sigma(ppbar -> WZ) = 5.0^{+1.8}_{-1.6} pb, consistent with the standard model expectation.