QCD matrix elements + parton showers: The NLO case

TL;DR

This paper introduces a process-independent method to combine NLO calculations with parton showers, reducing theoretical uncertainties and maintaining accuracy, demonstrated through W-boson production at the LHC.

Contribution

The authors develop a novel, automated technique that seamlessly integrates NLO matrix elements with parton showers, avoiding double counting and improving predictive precision.

Findings

Significant reduction in theoretical uncertainties.

Successful implementation in Sherpa event generator.

Enhanced accuracy in W-boson production simulations.

Abstract

We present a process-independent technique to consistently combine next-to-leading order parton-level calculations of varying jet multiplicity and parton showers. Double counting is avoided by means of a modified truncated shower scheme. This method preserves both the fixed-order accuracy of the parton-level result and the logarithmic accuracy of the parton shower. We discuss the renormalisation and factorisation scale dependence of the approach and present results from an automated implementation in the Sherpa event generator using the test case of W-boson production at the Large Hadron Collider. We observe a dramatic reduction of theoretical uncertainties compared to existing methods which underlines the predictive power of our novel technique.