The effects of O(α2) initial state QED corrections to e+e− → γ⁎/Z⁎ at very high luminosity colliders

Abstract

We present numerical results on the recently completed O(α2) initial state corrections to the process e+e−→γ⁎/Z⁎, 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 [1] in the non-logarithmic contributions at O(α2). The new result leads to a 4 MeV shift in the Z width considering the lower end s0=4mτ2 of the radiation region, which is larger than the present accuracy. A corresponding cut to s0/s=0.01 only implies a shift of 0.2 MeV. We present predictions on the radiative corrections to the central processes e+e−→γ⁎/Z⁎, e+e−→ZH and e+e−→tt‾ 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.