Related papers: Two-loop QED corrections with closed fermion loops…
In this article two-loop QED corrections to the muon decay and corrections of order $\alpha_s^2$ to the semileptonic decay of the bottom quark are considered. We compute the imaginary part of the four-loop diagrams contributing to the…
We investigate two-loop higher-order binding corrections to the fine structure, which contribute to the spin-dependent part of the Lamb shift. Our calculation focuses on the so-called ``two-loop self-energy'' involving two virtual closed…
We present closed analytic expressions of the electromagnetic vertex form factors for heavy quarks at the two-loop level in QCD for arbitrary momentum transfer. The calculation is carried out in dimensional regularization. The electric and…
We compute next-to-leading order virtual two-loop corrections to the process $gg\to ZZ$ in the low- and high-energy limits, considering the contributions with virtual top quarks. Analytic results for all 20 form factors are presented…
We compute the two-loop corrections to the coefficient of the b --> s gamma magnetic penguin present in the limits of heavy top and/or heavy higgs. This kind of corrections affects in a significant way the observables measured at LEP. On…
The hyperfine structure (hfs) and the g factor of a bound electron are caused by external magnetic fields. For the hfs, the magnetic field is due to the nuclear spin. A uniform-in-space and constant-in-time magnetic field is used to probe…
The finite nuclear size correction to the bound-electron g factor in hydrogenlike atoms is investigated in the range Z=1-20. An analytical formula for this correction which includes the non-relativistic and dominant relativistic…
Two-loop corrections with scalar and vector form factors are calculated for nuclear matter in the Walecka model. The on-shell form factors are derived from vertex corrections within the framework of the model and are highly damped at large…
We present an analysis of two-loop mixed QCD and electroweak corrections to the decay of the Z boson into light quarks. We find that the naive factorization of QCD and electroweak corrections does not describe correctly the two-loop…
We compute the electron $g$ factor to the $\mathcal{O}(\alpha^5)$ order on the lattice in quenched QED. We first study finite volume corrections in various IR regularization methods to discuss which regularization is optimal for our…
A new scheme for the numerical evaluation of the one-loop self-energy correction to all orders in Z \alpha is presented. The scheme proposed inherits the attractive features of the standard potential-expansion method but yields a…
The $O(\alpha)$ corrections to $\gamma\gamma --> f \bar f$ in the Standard Model are calculated for arbitrary, light fermions $f$. The relevant analytical results are listed in a form that is appropriate for practical applications, and…
The shielding of the nuclear magnetic moment by the bound electron in hydrogen-like ions is calculated ab initio with inclusion of relativistic, nuclear, and quantum electrodynamics (QED) effects. The QED correction is evaluated to all…
We present the one-loop QCD amplitudes for two external massless quarks and three external gluons ($\bar{q}qggg$). This completes the set of one-loop amplitudes needed for the next-to-leading-order corrections to three-jet production at…
The computation of the correction \Delta r 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.…
We calculate the dominant ${\rm O}\left(G_F^2M_H^4\right)$ two-loop electroweak corrections to the fermi\-onic decay widths of a heavy Higgs boson in the Standard Model. Use of the Goldstone-boson equivalence theorem reduces the problem to…
We report an ab initio calculation of the shielding of the nuclear magnetic moment by the bound electron in hydrogen-like ions. This investigation takes into account several effects that have not been calculated before (electron…
We calculate the standard model predictions for top quark pair production and decay into six fermions at a linear e+ e- collider. We include the factorizable electroweak O(alpha) corrections in the pole approximation and QED corrections due…
We calculate the two-loop QCD corrections to $gg \to ZZ$ involving a closed top-quark loop. We present a new method to systematically construct linear combinations of Feynman integrals with a convergent parametric representation, where we…
The calculation of the next-to-leading order QCD corrections to the production of a neutral Higgs-boson pair is briefly summarized. The dominant production mechanism is gluon fusion via top-quark loops, so that the QCD corrections can be…