Automated Predictions from Polarized Matrix Elements

TL;DR

This paper introduces an automated method for calculating polarized matrix elements in MadGraph5_aMC@NLO, enabling detailed simulations of polarized vector boson processes crucial for future high-precision collider experiments.

Contribution

The authors have developed and validated an automated approach for polarized matrix element computations within a widely used Monte Carlo framework, enhancing the simulation capabilities for polarization studies.

Findings

Good agreement with On-Shell Projection polarization studies

Demonstrated simulations of polarized weak gauge boson production and decay

Applicable to Standard Model and composite Higgs scenarios

Abstract

The anticipated experimental resolution and data cache of the High Luminosity Large Hadron Collider will enable precision investigations of polarization in multiboson processes. This includes, for the first time, vector boson scattering. To facilitate such studies, we report the automation of polarized matrix element computations in the publicly available Monte Carlo tool suite, MadGraph5_aMC@NLO. This enables scattering and decay simulations involving helicity-polarized asymptotic or intermediate states, preserving both spin-correlation and off-shell effects. As demonstrations of the method, we investigate the leading order production and decay of polarized weak gauge bosons in the process $pp \to j j W^+_\lambda W^-_{\lambda'}$, with helicity eigenstates $(\lambda,\lambda')$ defined in various reference frames. We consider the Standard Model at both $\mathcal{O}(\alpha^4)$ and $\mathcal{O}(\alpha^2 \alpha_s^2)$ as well as a benchmark composite Higgs scenario. We report good agreement with polarization studies based on the On-Shell Projection (OSP) technique. Future capabilities are discussed.