Precise Standard-Model predictions for polarised Z-boson pair production and decay at the LHC

TL;DR

This paper provides the most precise Standard Model predictions for polarised Z-boson pair production and decay at the LHC, combining NNLO QCD and NLO EW corrections, crucial for understanding electroweak symmetry breaking and new physics.

Contribution

First to combine NNLO QCD and NLO EW corrections for polarised Z-boson pairs, setting a new accuracy standard for LHC predictions.

Findings

Achieved state-of-the-art perturbative accuracy with combined corrections.

Compared different Monte Carlo strategies for signal definition and interference effects.

Analyzed impact of parton-shower matching and multi-jet merging on predictions.

Abstract

Providing accurate theoretical predictions in the Standard Model for processes with polarised electroweak bosons is crucial to understand more in-depth the electroweak-symmetry breaking mechanism and to enhance the sensitivity to potential new-physics effects. Motivated by the rapidly increasing number of polarisation analyses of di-boson processes with LHC data, we carry out a comprehensive study of the inclusive production of two polarised Z bosons in the decay channel with four charged leptons. We perform a detailed comparison of fixed-order predictions obtained with various Monte Carlo programs which rely on different signal-definition strategies, assessing non-resonant and interference effects by contrasting polarised results with unpolarised and full off-shell ones. For the first time, we accomplish the combination of NNLO QCD and NLO EW corrections, setting the new state-of-the-art perturbative accuracy for polarised Z-boson pairs at the LHC. The impact of parton-shower matching and multi-jet merging is investigated by scrutinising calculations obtained with event generators that are typically used in experimental analyses. Integrated and differential results are discussed in a realistic fiducial setup and compared to publicly available ATLAS results.