2. Vorlesung im Rahmen der Erwin-Schrödinger-Gastprofessur 2024
We present a systematic formalism based on a factorization theorem in Soft-Collinear Effective Theory (SCET) to describe non-global observables at hadron colliders, such as gap-between-jets cross sections. The cross sections are factorized into convolutions of hard functions, capturing the dependence on the partonic center-of-mass energy √s, and low-energy matrix elements, which are sensitive to the low scale Q0≪√s characteristic of the veto imposed on energetic emissions into the gap region between the jets. The scale evolution of both objects is governed by a renormalization-group equation, whose form we derive. With the help of this equation, we develop an EFT-based approach to the resummation of so-called “non-global logarithms'', including the “super-leading logarithms” discovered by Forshaw et al. in 2006, which only appear in hadron-collider processes.
Part 2:The super-leading logarithms arise from two soft Glauber-gluon interactions between the two colliding partons in the scattering process. Using the same formalism, we explore the contributions of multiple Glauber interactions. The “Glauber series“ simultaneously incorporates large double-logarithmic corrections together with higher-order exchanges of Glauber pairs associated with the large numerical factor (iπ)2. Numerical estimates for wide-angle gap-between-jet cross sections at the parton level show that, in particular for gg scattering at relatively small vetoes Q0, the contribution involving four Glauber exchanges gives a sizable correction and should not be neglected. We develop a resummation approach for the terms in the Glauber series in renormalization-group improved perturbation theory, including the running of the strong coupling αs(μ). We also show that the Glauber series itself can be resummed to all orders in the large-Nc limit.
