Search for: All records

A bstract Two-loop electroweak corrections to polarized Møller scattering are studied in two different schemes at low energies. We find the finite Q 2 corrections to be well under control. The hadronic and perturbative QCD corrections to the γZ two-point function are incorporated through the weak mixing angle at low energies, which introduce an error of 0 . 08 × 10 − 3 in the weak charge of the electron $$ {Q}_W^e $$ Q W e . Furthermore, by studying the scheme dependence, we obtain an estimate of the current perturbative electroweak uncertainty, $$ \delta {Q}_W^e $$ δ Q W e ≈ 0 . 23 × 10 − 3 , which is five times smaller than the precision estimated for the MOLLER experiment ( $$ \delta {Q}_W^e $$ δ Q W e = 1 . 1 × 10 − 3 ). Future work is possible to reduce the theory error further. 

In this proceeding, we highlight the computation of leading fermionic three-loop corrections to electroweak precision observables (EWPOs) accomplished recently. We summarize the numerical analysis and provide an outlook. 

A bstract Precision studies of the Higgs boson at future e + e − colliders can help to shed light on fundamental questions related to electroweak symmetry breaking, baryogenesis, the hierarchy problem, and dark matter. The main production process, e + e − → HZ , will need to be controlled with sub-percent precision, which requires the inclusion of next-to-next-to-leading order (NNLO) electroweak corrections. The most challenging class of diagrams are planar and non-planar double-box topologies with multiple massive propagators in the loops. This article proposes a technique for computing these diagrams numerically, by transforming one of the sub-loops through the use of Feynman parameters and a dispersion relation, while standard one-loop formulae can be used for the other sub-loop. This approach can be extended to deal with tensor integrals. The resulting numerical integrals can be evaluated in minutes on a single CPU core, to achieve about 0.1% relative precision. 

A bstract Measurements of electroweak precision observables at future electron-position colliders, such as the CEPC, FCC-ee, and ILC, will be sensitive to physics at multi-TeV scales. To achieve this sensitivity, precise predictions for the Standard Model expectations of these observables are needed, including corrections at the three- and four-loop level. In this article, results are presented for the calculation of a subset of three-loop mixed electroweak-QCD corrections, stemming from diagrams with a gluon exchange and two closed fermion loops. The numerical impact of these corrections is illustrated for a number of applications: the prediction of the W-boson mass from the Fermi constant, the effective weak mixing angle, and the partial and total widths of the Z boson. Two alternative renormalization schemes for the top-quark mass are considered, on-shell and $$ \overline{\mathrm{MS}} $$ MS ¯ . 

Phenomenologically relevant electroweak precision pseudo-observables related to Z-boson physics are discussed in the context of the strong experimental demands of future e+e− colliders. The recent completion of two-loop Z-boson results is summarized and a prospect for the 3-loop Standard Model calculation of the Z-boson decay pseudo-observable is given.