EVAluation of the Equivalent Vector Boson Approximation at highest energy colliders

TL;DR

This paper evaluates the accuracy of the Equivalent Vector Boson Approximation (EVA) at high-energy colliders, revealing significant process-dependent uncertainties and limitations in its predictive power for electroweak interactions.

Contribution

It provides a detailed analysis of EVA's performance across various processes at energies of 10 TeV and above, highlighting its limitations and the need for process-specific adjustments.

Findings

EVA's discrepancies with matrix-element predictions are process-dependent.

Uncertainties in EVA can reach up to 100% due to parameter dependencies.

Process-specific kinematic cuts may reduce EVA uncertainties.

Abstract

Collider processes at the highest available partonic center-of-mass energies - 10 TeV and above - exhibit a new regime of electroweak interactions where electroweak gauge bosons mostly act as quasi-massless partons in vector boson fusion processes. We scrutinize these processes using the Equivalent Vector boson Approximation (EVA) based on its implementation in the Monte Carlo generator framework Whizard. Using a variety of important physics processes, including top pairs, Higgs pairs, neutrino pairs, and vector boson pairs, we study the behavior of processes initiated by transverse and longitudinal vector bosons, both $W$ and $Z$ induced. By considering several distributions for each process, we conclude that: there is no universal, process-independent prescription which minimizes the discrepancies between EVA- and matrix-element-based predictions; even by resorting to process-by-process prescriptions, we typically observe significant observable-dependent effects; the uncertainties associated with parameter dependencies in the EVA can be as large as $\mathcal{O}$(100%), and can only possibly be reduced by careful process-dependent kinematical selections.