Probing the Structure of Jets: Factorized and Resummed Angularity Distributions in SCET

Using the framework of soft-collinear effective theory (SCET), we factorize and calculate e+e− angularity distributions, including perturbative resummation and the incorporation of a universal model for the nonperturbative soft function. Angularities τa are a class of event shapes varying in their sensitivity to the substructure of jets in the final state, controlled by a continuous parameter a < 2. We calculate the jet and soft functions in factorized angularity distributions for all a < 1 to first order in the strong coupling αs and resum large logarithms to next-to-leading logarithmic (NLL) accuracy. We employ a universal model for the nonperturbative soft function with a gap parameter which cancels the renormalon ambiguity in the partonic soft function.