Abstract
Factorization violating effects in hadron scattering are due mainly to spectator-spectator interactions. While it is known that these interactions cancel in inclusive cross sections, like for the Drell-Yan process, not much is known about for what classes of observables factorization is violated. We show that for pure Glauber ladder graphs, all amplitude-level factorization violating effects completely cancel at cross section level for any single-scale observable (such as hadronic transverse energy or beam thrust). This result disproves previous claims that these pure Glauber graphs are factorization-violating. Our proof exploits scale invariance of two-to-two scattering amplitudes in an essential way. The leading factorization-violating effects therefore come from graphs with at least one soft gluon, involving the Lipatov vertex off of the Glauber ladders. This implies that real soft radiation must be involved in factorization-violation, shedding light on the connection between factorization-violation and the underlying event.
Highlights
Factorization is essential to the predictive power of perturbative QCD at hadron colliders
We show that for pure Glauber ladder graphs, all amplitude-level factorization violating effects completely cancel at the cross section level for any single-scale observable
The cancellation we find implies that the differential cross section for any single-scale observable, such as hadronic transverse energy, or beam thrust, gets no contribution from pure-Glauber graphs
Summary
Factorization is essential to the predictive power of perturbative QCD at hadron colliders. There has been renewed interest in extending the CSS argument to other processes and understanding its failure This has been motivated by the advent of jet substructure techniques [8,9,10,11,12], where predictions of observables such as jet mass or beam thrust are apparently more sensitive to factorization violating effects than traditional kinematic observables, such as the jet pT spectrum. For these graphs, scale invariance is violated by quantum effects, and so factorization can be violated.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have