Complementarity between ILC250 and ILC-GigaZ

TL;DR

This paper discusses how the high-precision measurements at ILC250 could surpass LEP1/SLC in accuracy, impacting the indirect detection of new resonances and exploring the potential of running ILC at the Z pole with polarized electrons.

Contribution

It analyzes the complementarity between ILC250 and ILC-GigaZ in precision measurements and their implications for new physics sensitivity.

Findings

ILC250 will significantly improve fermion coupling measurements.

LEP1/SLC measurements are too imprecise compared to ILC250.

Running ILC at the Z pole with polarization could enhance sensitivity.

Abstract

In view of the very precise measurements on fermion couplings which will be performed at ILC250 with polarized beams, there is emerging evidence that the LEP1/SLC measurements on these couplings are an order of magnitude too imprecise to match the accuracies reachable at ILC250. This will therefore severely limit the indirect sensitivity to new resonances and require revisiting the possibility to run ILC at the Z pole with polarized electrons. This work was done as a contribution to the ESU 2018-2020.