arXiv subjects

W. Walter

Publications and source records attributed to W. Walter.

5 recordsLinked to original sources

arXiv2024

KIT Superconducting Undulator Development -- Story of a successful industrial collaboration & future prospects

Undulators are X-ray sources widely used in synchrotron storage rings and free-electron laser facilities. With the commercial availability of low-temperature superconductors, a new type of undulator was born, the superconducting undulator (SCU). In this context, the industrial cooperation between the Karlsruhe Institute of Technology and Bilfinger Nuclear and Energy Transition GmbH started more than 15 years ago. Since then, many projects have been successfully completed, leading to the production of the world's leading full-scale commercial SCUs based on conduction cooling. Starting with the SCU15, the first of its kind installed SCU providing light to a beamline, followed by the SCU20 installed and still in operation at the Karlsruhe Research Accelerator. The successful realisation of such SCUs has required the simultaneous development of appropriate measurement facilities such as CASPER I and CASPER II.

physics.acc-ph↗

arXiv2003

Complete fermionic two-loop results for the M_W-M_Z interdependence

The complete fermionic two-loop contributions to the prediction for the W-boson mass from muon decay in the electroweak Standard Model are evaluated exactly, i.e. no expansion in the top-quark and the Higgs-boson mass is made. The result for the W-boson mass is compared with the previous result of an expansion up to next-to-leading order in the top-quark mass. The predictions are found to agree with each other within about 5 MeV. A simple parameterization of the new result is presented, approximating the full result better than 0.4 MeV for M_H < 1 TeV.

hep-ph↗

arXiv2003

Electroweak two-loop corrections to the MW-MZ mass correlation in the Standard Model

Recently exact results for the complete fermionic two-loop contributions to the prediction for the W-boson mass from muon decay in the electroweak Standard Model have been published [hep-ph/0007091]. This paper illustrates the techniques that have been applied for this calculation, in particular the renormalisation procedure and the treatment of IR-divergent QED contributions. Numerical results are presented in terms of simple parametrisation formulae and compared in detail with a previous result of an expansion up to next-to-leading order in the top-quark mass. An estimate of the remaining theoretical uncertainties of the MW-prediction from unknown higher-order corrections is given. For the bosonic two-loop corrections a partial result is presented, yielding the Higgs-mass dependence of these contributions.

hep-ph↗

arXiv2001

Two-loop electroweak contributions to $Δr$

A review is given on the quantum correction $Δr$ in the $W$--$Z$ mass correlation at the electroweak two-loop level, as derived from the calculation of the muon lifetime in the Standard Model. Exact results for $Δr$ and the $W$-mass prediction including ${\mathcal{O}}(α^2)$ corrections with fermion loops are presented and compared with previous results of a next-to-leading order expansion in the top-quark mass.

hep-ph↗

arXiv2000

Calculation of fermionic two-loop contributions to muon decay

The computation of the correction Δr in the W-Z mass correlation, derived from muon decay, is described at the two-loop level in the Standard Model. Technical aspects which become relevant at this level are studied, e.g. gauge-parameter independent mass renormalization, ghost-sector renormalization and the treatment of γ_5. Exact results for Δr and the W mass prediction including O(α^2) corrections with fermion loops are presented and compared with previous results of a next-to-leading order expansion in the top-quark mass.

hep-ph↗