Event-by-event weighting at next-to-leading order

TL;DR

The paper introduces a novel method for assigning NLO weights to LO phase space configurations at hadron colliders, enabling more precise calculations and applications like matrix element methods at NLO.

Contribution

It presents a new phase space mapping technique that cancels singularities at each Born phase space point, facilitating NLO calculations and extensions of matrix element methods.

Findings

Allows NLO weights to be assigned to LO configurations

Enables extension of matrix element methods to NLO

Facilitates applications in Higgs physics at the LHC

Abstract

We present a general method of associating next-to-leading order weights to leading order phase space configurations at hadron colliders. The method relies on a re-organization of phase space for the real radiation contributions, defining a one-to-many map such that each point in the real phase space is associated with a distinct Born topology. As a result virtual and real singularities cancel at each Born phase space point. The new phase space maps can be used in a traditional approach for NLO calculations. However, interesting applications arise when one instead integrates out the real radiation up to a specified scale. This allows one to define NLO weights for individual phase space points that are present at LO. This method allows for the extension of matrix element methods to next-to-leading order, even in the presence of jets. We discuss some recent applications of the matrix element method to Higgs physics at the LHC.