# Investigation of beam self-polarization in the future $e^{+}e^{-}$ circular collider

## TL;DR

This paper explores the potential for beam self-polarization in the future FCC-$e^{+}e^{-}$ collider, analyzing simulation results to assess the feasibility of using self-polarized leptons for precise energy measurements.

## Contribution

It presents the first simulation-based investigation into beam self-polarization in the FCC-$e^{+}e^{-}$, considering realistic errors and misalignments.

## Key findings

- Preliminary simulations show potential for self-polarization under certain conditions.
- Quadrupole misalignments and BPM errors impact polarization levels.
- Self-polarization could enhance energy measurement precision.

## Abstract

The use of resonant depolarization has been suggested for precise beam energy measurements (better than 100 keV) in the $e^{+}e^{-}$ Future Circular Collider (FCC-$e^{+}e^{-}$) for Z and WW physics at 45 and 80 GeV beam energy respectively. Longitudinal beam polarization would benefit the Z peak physics program; however it is not essential and therefore it will be not investigated here. In this paper the possibility of self-polarized leptons is considered. Preliminary results of simulations in presence of quadrupole misalignments and beam position monitors (BPMs) errors for a simplified FCC-$e^{+}e^{-}$ ring are presented.

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Source: https://tomesphere.com/paper/1705.03003