Johannes Blümlein - The effects of $O(\alpha^2)$ initial state QED corrections to $e^+ e^- \rightarrow \gamma^*/Z^*_0$ at very high luminosity colliders

Thursday, 5 March 2020 from to (Europe/Amsterdam)
at Nikhef
We present the recently completed O(α2) initial state corrections to the process $e^+ e^- \rightarrow \gamma^*/Z_0^*$ which is a central process at past and future high energy and high luminosity colliders for precision measurements of the properties of the $Z$-boson, the Higgs boson, and the top quark. We observe differences to an earlier result in the non-logarithmic contributions at
$O(\alpha^2)$. The new result leads to a 4 MeV shift in the Z width considering the lower end $s_0 = 4 m_\tau^2 of the radiation region, which is larger than the present accuracy. We present predictions on the radiative corrections to the central processes $e^+ e^- \rightarrow \gamma^*/Z_0^*, e^+e^- \rightarrow  Z_0 H_0$ and $e^+ e^- \rightarrow  t \bar{t}$ planned at future colliders like the ILC, CLIC, FCC_ee and CEPC to measure the mass and the width of the Z boson, the Higgs boson and the top quark, for which the present corrections are significant.