Using an Effective Charges Method to extract image from event shape moments in image annihilation Original Research Article

We use an Effective Charges (ECH) method to extract image, and hence image, from event shape moments in image annihilation. We compare these results with ones obtained using standard image perturbation theory. The ECH method at NLO is found to perform better than standard image perturbation theory when applied to means of event shape observables. For example, when we apply the NLO ECH method to image we get image. However ECH at NNLO is found to work less well than ECH at NLO, and the ECH method also fails to describe data for higher moments of event shapes. We attempt to explain this by considering the ECH β-function as an asymptotic series. We also examine the effect of adding two different models for non-perturbative power corrections to the perturbative approximation given by the ECH method and image perturbation theory. Whilst only small power corrections are required when using ECH at NLO, it is found that these models are insufficient to counteract the undesirable behaviour of ECH at NNLO.