Related papers: O(N_f\alpha^2) Corrections to Muon Decay
We provide a compendium of techniques that can be used to compute $O(N_f\alpha^2)$ corrections to low-energy electroweak processes. Specifically, these are the 2-loop electroweak corrections containing a light fermion loop. It is shown that…
The complete O(N_f alpha^2) weak contributions to the muon lifetime, denoted as Delta r^(2), are calculated in the MS-bar renormalization scheme. These come from 2-loop Feynman diagrams containing a loop formed by complete generations of…
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 present results for the corrections of order alpha^2 (Z alpha) E_F to the hyperfine splitting of muonium. We compute all the contributing Feynman diagrams in dimensional regularization and a general covariant gauge using a mixture of…
The O(N_f alpha^2) electroweak radiative corrections to the Thomson scattering matrix element are calculated for a general renormalization scheme with massless fermions. All integrals can be evaluated exactly in dimensional regularization…
Recently, first results were presented for two-loop corrections to the muon (g-2) from fermion/sfermion loops in the MSSM. These corrections were shown to be generally large and even logarithmically enhanced for heavy sfermions. Here, full…
We present an analytical calculation of additional real or virtual radiation of the light fermion pair in the fermionic decay of the Higgs boson $ H \to f_1\bar f_1$ for arbitrary ratios of the Higgs boson mass to the $f_1$ fermion mass.…
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 present a determination of a new class of three-loop Feynman diagrams describing heavy-to-light transitions. We apply it to find the O(alpha_s^2) corrections to the top quark decay t -> bW and to the distribution of lepton invariant mass…
Two-loop contributions to the muon (g-2) from fermion/sfermion loops in the MSSM are presented, and an overview of the full MSSM prediction for (g-2) is given with emphasis on the behaviour in scenarios which are compatible with LHC data,…
First results on the radiative corrections of order O(N_f\alpha_s\alpha) are presented for the off-shell production of W or Z bosons at the LHC, where N_f is the number of fermion flavours. These corrections comprise all diagrams at…
Details of a recent calculation of O(alpha_s^2) corrections to the decay b -> c,l,nu_l, taking into account the c-quark mass, are described. Construction of the expansion in the mass ratio m_c/m_b as well as the evaluation of new four-loop…
O(\alpha^2 \ln(m_\mu/m_e)) corrections to electron energy spectrum in muon decay are computed using perturbative fragmentation function approach. The magnitude of these corrections is comparable to anticipated precision of the TWIST…
The inclusive radiative decay of the B meson is known to provide strong constraints on many popular extensions of the Standard Model. Such constraints crucially depend on precision of the Standard Model predictions. One of the main…
We present the calculation of the so far missing ${\cal O}(\alpha^2\alpha_\mathrm{s})$ corrections to the quantity $\Delta r$, which relates the Fermi constant to the W-boson mass, and enables precision predictions of the latter. While the…
We compute O(alpha_s^2) QCD corrections to the lepton invariant mass spectrum in the decay b --> u l nu_l, relevant for the determination of the CKM matrix element |V_{ub}|. Our method can also be used to evaluate moments of the lepton…
Low- and intermediate mass Higgs bosons decay preferably into fermion pairs. The one-loop electroweak corrections to the respective decay rates are dominated by a flavour-independent term of ${\cal O}(G_Fm_t^2)$. We calculate the two-loop…
We compute the two-loop corrections of O(alpha_s^2) to the Yukawa couplings in the framework of the Minimal Supersymmetric Standard Model (MSSM). The calculation is performed using the effective Lagrangian approach under the approximation…
We consider the impact of O(alpha^2) hadronic corrections to the energy spectrum of the decay electron in muon decay. We find that the correction can be described, within good approximation, by a linear function in the electron energy.…
Of the the three best-measured electroweak observables, $\alpha$, $G_\mu$ and $M_Z$, the first two are extracted from low-energy processes. Both $G_\mu$ and $M_Z$ are now known to an accuracy of about 2 parts in $10^5$ and there is a…