Hadron collider limits on anomalous WWγ couplings

A next-to-leading log calculation of the reactions pp and p bar p→W±γX is presented including a triboson gauge coupling from non-standard-model contributions. The additional term arises by considering the standard model as a low energy effective theory. Two approaches are made for comparison. The first approach considers the triboson WWγ coupling as being uniquely fixed by tree level unitarity at high energies to its standard model form and, consequently, suppresses the non-standard-model contributions with form factors. The second approach is to ignore such considerations and calculate the contributions to non-standard-model triboson gauge couplings without such suppressions, using the first term in the momentum expansion of an effective chiral Lagrangian. It is found that at Fermilab Tevatron energies the two approaches do not differ much in quantitative results, while at large Hadron Collider (LHC) energies the two approaches give significantly different predictions for production rates. At the Tevatron and LHC, however, the sensitivity limits on the anomalous coupling of WWγ are too weak to usefully constrain parameters in the chiral Lagrangian