Joint resummation of two angularities at next-to-next-to-leading logarithmic order

Multivariate analyses are emerging as important tools to understand properties of hadronic jets, which play a key role in the LHC experimental program. We take a first step towards precise and differential theory predictions, by calculating the cross section for e⁺e⁻ → 2 jets differential in the angularities e_α and e_β. The logarithms of e_α and e_β in the cross section are jointly resummed to next-to-next-to-leading logarithmic accuracy, using the SCET₊ framework we developed, and are matched to the next-to-leading order cross section. We perform analytic one-loop calculations that serve as input for our numerical analysis, provide controlled theory uncertainties, and compare our results to Pythia. We also obtain predictions for the cross section differential in the ratio e_α/e_β , which cannot be determined from a fixed-order calculation. The effect of nonperturbative corrections is also investigated. Using EVENT2, we validate the logarithmic structure of the single angularity cross section predicted by factorization theorems at O(α²_s), highlighting the importance of recoil for specific angularities when using the thrust axis as compared to the winner-take-all axis.