Probing the $WW\gamma$ vertex at hadron colliders

TL;DR

This paper introduces a model-independent method to constrain anomalous $\gamma WW$ couplings at hadron colliders using three novel observables derived from the differential cross-section of specific processes, applicable to both $par{p}$ and $pp$ colliders.

Contribution

It proposes a new set of observables that allow direct measurement of $\Delta ext{kappa}$ and impose sum rules on other anomalous couplings without simplifying assumptions.

Findings

The method enables direct determination of $\Delta ext{kappa}$.

It provides sum rules for remaining anomalous couplings.

Applicability to both $par{p}$ and $pp$ colliders is demonstrated.

Abstract

We present a new, model independent method for extracting bounds for the anomalous $\gamma WW$ couplings from hadron collider experiments. At the partonic level we introduce a set of three observables which are constructed from the unpolarized differential cross-section for the process $d\bar{u}\to W^{-}\gamma$ by appropriate convolution with a set of simple polynomials depending only on the center-of-mass angle. One of these observables allows for the direct determination of the anomalous coupling usually denoted by $\Delta\kappa$, without any simplifying assumptions, and without relying on the presence of a radiation zero. The other two observables impose two sum rules on the remaining three anomalous couplings. The inclusion of the structure functions is discussed in detail for both $p\bar{p}$ and $pp$ colliders. We show that, whilst for $p\bar{p}$ experiments this can be accomplished straightforwardly, in the $pp$ case one has to resort to somewhat more elaborate techniques, such as the binning of events according to their longitudinal momenta.