# Merging NLO Multi-jet Calculations with Improved Unitarization

## TL;DR

This paper introduces an algorithm that combines NLO multi-jet calculations with parton showers, reducing uncertainties and improving predictions for collider observables involving multiple jets.

## Contribution

It presents a novel unitarized merging algorithm that integrates higher-order matrix elements with parton showers, enhancing accuracy for multi-jet events.

## Key findings

- Reduced scale uncertainties for jet observables
- Improved predictions for multi-jet collider events
- Implementation in the Herwig event generator

## Abstract

We present an algorithm to combine multiple matrix elements at LO and NLO with a parton shower. We build on the unitarized merging paradigm. The inclusion of higher orders and multiplicities reduce the scale uncertainties for observables sensitive to hard emissions, while preserving the features of inclusive quantities. The combination allows further soft and collinear emissions to be predicted by the all-order parton shower approximation. We inspect the impact of terms that are formally but not parametrically negligible. We present results for a number of collider observables where multiple jets are observed, either on their own or in the presence of additional uncoloured particles. The algorithm is implemented in the event generator Herwig.