# The Z boson spin observables as messengers of new physics

## TL;DR

This paper shows that analyzing the spin observables of the Z boson through angular asymmetries can effectively distinguish between standard production mechanisms and potential new physics signals at the LHC.

## Contribution

It introduces a method to use Z boson spin multipole parameters as a tool for identifying new physics in collider experiments.

## Key findings

- Multipole parameters can differentiate known Z production from new physics signals.
- Angular asymmetries enable extraction of spin observables from decay products.
- Method applied to various processes including Z+jets, Z+MET, and heavy resonance decays.

## Abstract

We demonstrate that the 8 multipole parameters describing the spin state of the $Z$ boson are able to disentangle known $Z$ production mechanisms and signals from new physics at the LHC. They can be extracted from appropriate asymmetries in the angular distribution of lepton pairs from the $Z$ boson decay. The power of this analysis is illustrated by (i) the production of $Z$ boson plus jets; (ii) $Z$ boson plus missing transverse energy; (iii) $W$ and $Z$ bosons originating from the two-body decay of a heavy resonance.