Resolve flavour-dependent tensions in the weak effective mixing angle

Determine whether the observed tensions between flavour-specific determinations of the weak effective mixing angle (sin^2 θ_eff) from different fermion final states can be resolved by measurements at future e+e− colliders, and establish a consistent framework that reconciles these discrepancies using high-precision two-fermion observables at the Z pole.

Background

The document outlines that future e+e− colliders will dramatically improve precision in electroweak measurements, particularly at the Z pole, where statistical uncertainties will be far smaller than past LEP/SLC results. Within this context, it notes persistent flavour-dependent tensions in the determination of the weak effective mixing angle, an essential parameter for precision tests of the Standard Model.

Clarifying or resolving these tensions is critical for global electroweak fits and for interpreting potential deviations as signs of new physics. The authors highlight the need for improved measurements and systematics control across different flavours to address this unresolved issue.