L. Dixon, SLAC

Title: “Correlating Energies in QCD”

Abstract:  The road from scattering amplitudes to collider experiments can be complex in QCD.  For example, only “infrared-safe” observables are dominated by short distances and computable perturbatively.  Many of these observables, such as QCD jets, have an iterative definition that makes analytic computation intractable.  In contrast, the energy-energy correlation in electron-positron annihilation has a fairly simple definition, given 40 years ago. It depends only on the angle between two detectors.  It has now been computed through next-to-next-to-leading order (NNLO) in the strong coupling, and through NLO analytically for arbitrary angular separation.  I will review this analytic structure and the status of this observable, both for generic angles and for small angles and large (back-to-back) angles, where large logarithms can be resummed, potentially allowing for an improved measurement of the strong coupling. Similar observables can be defined at the LHC and could serve as computable, infrared-safe jet substructure variables.