Searching for the dark photon at the Future Circular Lepton Collider

Abstract

In the context of future electroweak precision measurements at the Future Circular Lepton Collider (FCC-ee), we consider recent proposals aimed at finding signatures of physics beyond the Standard Model. In particular, we focus on recent novel suggestions for very precise direct measurements of ${\alpha }_{\mathrm{em}}(M_Z^2)$. It is shown that at a level of precision of order $10^{-5}$, the effects of a dark photon may be very significant.

Comments: 6 pages, 2 figures. Revised to match the published version