Graduate student Andrew Meade and Professor Ben Brau have made a first measurement of the ratio of production of W and Z bosons in events that also contain a jet. The W and Z are heavy (80-90 times the proton mass!) cousins of the massless photon, and are responsible for the weak nuclear force. Many theories for new physics beyond the standard model include couplings between the W and Z and the new particles. Often, these couplings lead to signatures involving production of W and/or Z particles accompanied by jets. By measuring the ratio of production of W and Z along with a jet, we are able to achieve cancellation of many sources of systematic uncertainties, enabling a precision test of the physics of boson plus jet production, so-called perturbative QCD. We further measure this quantity versus the minimum transverse momentum of the jet, increasing the sensitivity of the comparison with theory. This kind of measurement is also sensitive to deviations in the production rates of either the W or Z, so if we see a discrepancy from prediction, it might be our first hint that there is new physics coupling to the W or Z.

This measurement is featured in a Cern Courier article in the November issue.

This plot shows the ratio along with several different predictions using different algorithms for comparison. The ratio is plotted versus the minimum jet transverse momentum required.