Exploring the $ u$SMEFT with Missing Energy and Displaced Vertex Signatures at FCC-ee
Patrick Bolton, Frank F. Deppisch, Suchita Kulkarni, Chayan Majumdar, Wenna Pei · 2025
We study the potential of FCC-ee to probe GeV-scale heavy neutral leptons (HNLs) in Standard Model extensions using the effective field theory (EFT) approach. Focusing on $ u$SMEFT operators at dimension $d \leq 7$, we study their impact on HNL production and decay at an $e^+e^-$ collider. For Majorana and Dirac HNLs, sensitivities to the active-sterile mixing and EFT Wilson coefficients are evaluated for monophoton searches and displaced vertex signatures at FCC-ee. Constraints on Wilson coefficients are translated into lower bounds on the new physics scale.