Interplay of Beam Polarisation and Systematic Uncertainties in Electroweak Precision Measurements at Future $e^+ e^-$ Colliders

TL;DR

This paper investigates how beam polarization at future $e^+ e^-$ colliders can help mitigate systematic uncertainties in electroweak precision measurements, complementing statistical improvements and enhancing the accuracy of Standard Model tests.

Contribution

It is the first study to evaluate the impact of beam polarization on systematic uncertainties in electroweak precision observables at future colliders.

Findings

Beam polarization can reduce systematic uncertainties in measurements.

Different polarization configurations affect the sensitivity to systematic effects.

Systematic uncertainties can be constrained through combined fits of observables.

Abstract

Future high-energy $\textrm{e}^+\textrm{e}^-$ colliders will provide some of the most precise tests of the Standard Model. Statistical uncertainties on electroweak precision observables and triple gauge couplings are expected to improve by orders of magnitude over current measurements. This provides a new challenge in accurately assessing and minimizing the impact of experimental systematic uncertainties. Beam polarization may hold a unique potential to isolate and determine the size of systematic effects. So far, studies have mainly focused on the statistical improvements from beam polarisation. This study aims to assess, for the first time, its impact on systematic uncertainties. A combined fit of precision observables, such as chiral fermion couplings and anomalous triple gauge couplings, together with experimental systematic effects is performed on generator-level differential distribution of 2-fermion and 4-fermion final-states. Different configurations of available beam polarisations and luminosities are tested with and without systematic effects, and will be discussed in the context of the existing projections on fermion and gauge boson couplings from detailed experimental simulations.