Vincia for Hadron Colliders

TL;DR

This paper introduces Vincia 2.0, a public implementation of antenna-based QCD parton showers for hadron colliders, capturing both collinear and soft singularities with advanced phase-space and matrix-element matching.

Contribution

It presents the first public antenna-based QCD shower implementation with exact phase-space factorization and matrix-element corrections up to high orders, improving accuracy for collider simulations.

Findings

Incorporates $2\to 3$ antenna functions capturing soft and collinear singularities.

Allows non-ordered emissions with suppression, enhancing shower realism.

Includes matrix-element corrections up to 4 jets and for Drell-Yan and Higgs processes.

Abstract

We present the first public implementation of antenna-based QCD initial- and final-state showers. The shower kernels are $2\to 3$ antenna functions, which capture not only the collinear dynamics but also the leading soft (coherent) singularities of QCD matrix elements. We define the evolution measure to be inversely proportional to the leading poles, hence gluon emissions are evolved in a $p_\perp$ measure inversely proportional to the eikonal, while processes that only contain a single pole (e.g., $g\to q\bar{q}$) are evolved in virtuality. Non-ordered emissions are allowed, suppressed by an additional power of $1/Q^2$. Recoils and kinematics are governed by exact on-shell $2\to 3$ phase-space factorisations. This first implementation is limited to massless QCD partons and colourless resonances. Tree-level matrix-element corrections are included for QCD up to $\mathcal{O}(\alpha_s^4)$ (4 jets), and for Drell-Yan and Higgs production up to $\mathcal{O}(\alpha_s^3)$ ($V/H$ + 3 jets). The resulting algorithm has been made publicly available in Vincia 2.0.