Asymptotcity of QCD and massive, oriented event-shapes

Résumé

The study of the large order behavior of infinite power series in QCD, which are the fundamental objects in perturbation theory, is adressed in the context of the large-b0 limit. A systematic formalism to extract closed expressions and renormalons is developed for regular series and extended to series with cusp anomalous dimension for the first time. A number of applications, such as short-distance mass-schemes and SCET and bHQET factorization theorems for dijets are considered in detail. The problem of asymptotic separation in the tau spectral moments is studied for the gluon-condensate Borel model, and the differences between the FOPT (convergent) and CIPT (divergent) schemes are clearly stablished. The fixed-order NLO computation of the event-shape distribution of e^+e^ to hadrons is presented for massive event-shapes and with explicit orientation of the thrust axis.