Analysis of theWWγvertex: Form-factor and anomalous-magnetic-moment effects

We examine the possibility of placing limits on the composite structure of the W boson by looking for form-factor effects as well as a W anomalous magnetic moment (${\mu }_W$) in the processes W→eνγ, γe→Wν, and ν¯e→Wγ. We find the most sensitive reaction to variation in the magnetic-moment parameter ${\kappa }_W$ is γe→Wν, which should be accessible at the Stanford Linear Collider and CERN LEP. We find that all three processes are quite sensitive to form-factor effects for a compositeness scale in the range 100<Λ<350 GeV. From these reactions future experiments should be able to observe W compositeness from the effects of a nonstandard ${\kappa }_W$, form factors, or both. If such effects are not observed, stringent limits on W compositeness can be obtained from these reactions.