Away-from-jet energy flow

TL;DR

This paper analyzes energy flowing away from hard jets in high-energy QCD processes, focusing on the observable E_out in a region away from jets. It develops an analytic single-log resummation in the large-N_c limit by mapping soft emissions to colour dipole radiation and deriving an evolution equation for the dipole distribution G_{ab}(Δ). The resummation splits into a Sudakov bremsstrahlung factor and a universal soft secondary-branching component, with geometry entering through the region in and the jet directions. At large Δ, the interjet distribution exhibits a universal Gaussian suppression governed by soft dipole dynamics, while the buffer region around the emitters shrinks exponentially, a behavior corroborated by previous numerical studies and extendable to DIS and hadron-hadron collisions. The results also indicate non-perturbative power corrections through the Δ parameter and highlight how underlying events influence hadronic collisions.

Abstract

We consider interjet observables in hard QCD processes given by the energy flow E_out in a region away from all hard jets. Here the QCD radiation is depleted (E_out << Q), and therefore these observables provide ideal means to study non-perturbative effects. We derive an evolution equation (in the large N_c limit) which resums, for large Q/E_out, all leading terms arising from large angle soft emission (double logarithms are absent). We discuss the analytical features of the result and identify universal and geometry-dependent contributions. Our analysis confirms features found using numerical methods by Dasgupta and Salam.