@misc{10481/112349,
year = {2026},
month = {2},
url = {https://hdl.handle.net/10481/112349},
abstract = {The next generation of high-luminosity electron-positron colliders, such as the electron-positron Future
Circular Collider and the Circular Electron-Positron Collider operating at the Z pole (TeraZ), is expected to
deliver unprecedented precision in electroweak measurements. These precision observables are typically
interpreted within the Standard Model effective field theory (SMEFT), offering a powerful tool to constrain
new physics. However, the large number of independent SMEFT operators allows for the possibility of
blind directions, parameter combinations to which electroweak precision data are largely insensitive. In this
work, we demonstrate that such blind directions are not merely an artifact of agnostic effective field theory
scans, but arise generically in realistic ultraviolet completions involving multiple heavy fields. We identify
several concrete multifield extensions of the Standard Model whose low-energy SMEFT projections align
with known blind subspaces, and show that these persist even after accounting for renormalization group
evolution and finite one-loop matching effects. Our analysis shows that TeraZ will set a new benchmark in
precision for indirect searches, but fully probing the space of possible ultraviolet physics requires going
beyond this stage. Later electron-positron Future Circular Collider runs at higher center-of-mass energies,
together with the hadron-hadron Future Circular Collider, will provide the necessary complementary
probes, enabling a far more complete exploration of the SMEFT parameter space.},
organization = {MICIU/AEI/10.13039/501100011033 and ERDF/EU - (Grants No. PID2022-139466NB-C22 and No. PID2021-128396NB-I00)},
organization = {Junta de Andalucía Grants (No. FQM 101 and No. P21-00199)Junta de Andalucía Grants (No. FQM 101 and No. P21-00199)},
organization = {The Royal Society -  (No. AL-231018 and No. IES-R1-221239)},
organization = {Ramón y Cajal program - (RYC2019-027155-I and RYC2021-030842-I)},
publisher = {APS Journals},
title = {Potential blind directions at TeraZ},
doi = {10.1103/47fb-8vxy},
author = {Rodríguez Chala, Mikael and Criado, Juan Carlos},
}