Andrew Larkoski - IRC Safety vs. Calculability (1/3)

Thursday 20 Mar 2014, 14:00 → 16:00 Europe/Brussels

E/3rd floor-E.361 - Meeting room (E.361) (Marc de Hemptinne (chemin du Cyclotron, 2, Louvain-la-Neuve))

Infrared and collinear (IRC) safety is the guiding principle for the calculability of cross sections of exclusive observables in fixed-order perturbation theory. However, motivated by recent results in jet substructure, requiring IRC safety can be excessively constraining and superficially prevents detailed theoretical analyses of many interesting observables. In this talk, I will review IRC safety and give examples of observables that are not IRC safe but whose cross sections can nevertheless be computed in perturbation theory, referred to as "Sudakov safety". The structure of the cross sections of Sudakov safe observables explicitly illustrates their IRC unsafety and demonstrates that perturbation theory is much richer than fixed-order calculations suggest.