Glauber Gluons and Multiple Parton Interactions

Abstract

We show that for hadronic transverse energy $E_T$ in hadron-hadron collisions, the classic Collins-Soper-Sterman (CSS) argument for the cancellation of Glauber gluons breaks down at the level of two Glauber gluons exchanged between the spectators. Through an argument that relates the diagrams with these Glauber gluons to events containing additional soft scatterings, we suggest that this failure of the CSS cancellation actually corresponds to a failure of the `standard' factorisation formula with hard, soft and collinear functions to describe $E_T$ at leading power. This is because the observable receives a leading power contribution from multiple parton interaction (or spectator-spectator Glauber) processes. We also suggest that the same argument can be used to show that a whole class of observables, which we refer to as MPI sensitive observables, do not obey the standard factorisation at leading power. MPI sensitive observables are observables whose distributions in hadron-hadron collisions are disrupted strongly by the presence of multiple parton interactions (MPI) in the event. Examples of further MPI sensitive observables include the beam thrust $B_{a,b}^{+}$ and transverse thrust.

24 pages, 8 figures

References in corpus (9)

• Herwig++ Physics and Manual
• Drell-Yan production at small q_T, transverse parton distributions and the collinear anomaly
• QCD transverse-momentum resummation in gluon fusion processes
• Non-perturbative QCD effects in jets at hadron colliders
• The Quark Beam Function at NNLL
• Simulation of multiple partonic interactions in Herwig++
• Double Parton Scattering Singularity in One-Loop Integrals
• On Glauber modes in Soft-Collinear Effective Theory
• Soft-Gluon Cancellation, Phases and Factorization with Initial-State Partons

Cited by in corpus (6)

• Resummation of Double-Differential Cross Sections and Fully-Unintegrated Parton Distribution Functions
• Dissecting Soft Radiation with Factorization
• Rapidity-Dependent Jet Vetoes
• Ultraviolet divergences and factorization for coordinate-space amplitudes
• The Fully-Differential Quark Beam Function at NNLO
• The Evolution of Soft Collinear Effective Theory