# Polarimetry at the ILC

## TL;DR

This paper presents a unified method combining polarimeter data and collision measurements to accurately determine the luminosity-weighted polarization at the ILC, accounting for uncertainties and correlations.

## Contribution

It introduces a novel integrated approach that combines cross section and polarimeter data for polarization measurement at the ILC, including uncertainty management.

## Key findings

- Fast spin flip frequency reduces systematic uncertainty.
- Non-perfect helicity reversal can be compensated within the approach.
- The method achieves permille-level polarization accuracy.

## Abstract

At the ILC, the luminosity-weighted average polarization at the IP needs to be determined at the permille-level. In order to reach this goal, the combined information from the polarimeter and the collision data is required. In this study, a unified approach will be presented, which for the first time combines the cross section measurements with the expected constraints from the polarimeters. Hereby, the statistical and systematical uncertainties are taken into account, including their correlations. This study shows that a fast spin flip frequency is required because it easily reduces the systematic uncertainty, while a non-perfect helicity reversal can be compensated for within the unified approach. The final goal is to provide a realistic estimation of the luminosity-weighted average polarization at the IP to be used in the physic analyses.