# The Z Penguin in Generic Extensions of the Standard Model

## TL;DR

This paper calculates the one-loop Z penguin contribution in generic Standard Model extensions with unitarity, providing a finite, renormalized result that aids in interpreting LHC flavor observables for new physics.

## Contribution

It derives a finite, unitarity-consistent expression for the Z penguin in generic models, simplifying the analysis of flavor observables in new physics scenarios.

## Key findings

- Derived a finite Z penguin expression using Slavnov-Taylor identities.
- Showed the impact of unitarity on renormalization of flavor observables.
- Provided tools for interpreting LHC results in terms of new physics models.

## Abstract

Precision flavour observables play an important role in the interpretation of results at the LHC in terms of models of new physics. We present the result for the one-loop Z penguin in generic extensions of the standard model which exhibit exact perturbative unitarity. We use Slavnov-Taylor identities to study the implications of unitarity on the renormalisation of the Z penguin, and derive a manifestly finite result that depends on a reduced set of physical couplings.