Color coherence in multi-jet final states

TL;DR

This paper investigates the impact of color coherence effects in multi-jet final states at high-energy colliders, highlighting their partial treatment in current models and presenting a method to sum these effects to all orders using advanced Monte Carlo techniques.

Contribution

It introduces a novel approach to include all-order coherence effects in multi-jet simulations via transverse-momentum dependent matrix elements in Monte Carlo methods.

Findings

Coherence effects are significant at all orders in alpha_s.

Standard shower algorithms partially include coherence effects.

The proposed method effectively sums coherence effects to all orders.

Abstract

We discuss coherent QCD radiation from space-like parton branching and its effects on multi-jet final states at high-energy hadron colliders. Coherence effects for small longitudinal momentum fractions x are not included in the branching algorithms of standard shower Monte Carlo event generators. On the other hand, they are taken into account only partially in perturbative next-to-leading-order calculations for multi-jets. Such effects are present to all orders in alpha_s and can become logarithmically enhanced with \sqrt{s} / E_T, where E_T is the hardest jet transverse energy. We present results of summing coherence effects to all orders by parton-branching Monte Carlo methods based on transverse-momentum dependent matrix elements.