A detailed study on the prospects for a $$ \textrm{t}\overline{\textrm{t}} $$ threshold scan in e+e− collisions

A bstract A scan of the beam energy across the top quark pair $$ \left(\textrm{t}\overline{\textrm{t}}\right) $$ t t ¯ production threshold is part of the program of future Higgs, top, and electroweak factory projects. In this paper, we provide projections for the achievable precision in the top quark mass ( m t ), width (Γ t ), and Yukawa coupling ( y t ) at the electron-positron (e + e − ) stage of the Future Circular Collider (FCC-ee). The study includes a detailed assessment of parametric and systematic uncertainties, as well as a rigorous estimate of the effect of point-to-point correlations. We project that m t and Γ t can be determined with an experimental precision of 6.8 and 11.5 MeV, respectively, when m t is defined in the potential-subtracted (PS) scheme. The impact of theoretical uncertainties due to missing higher orders is found to be of about 35 (25) MeV on m t (Γ t ) at N 3 LO in non-relativistic QCD. Therefore, improvements in the theoretical accuracy, which is an active area of development, are key to match the achievable experimental precision at a future e + e − collider. We also explore the prospects for a measurement of y t at FCC-ee via a dedicated run above the $$ \textrm{t}\overline{\textrm{t}} $$ t t ¯ production threshold.