The O(α mt m2 W ) and O(ααs mt m2 W ) corrections to the partial decay width Γ(Z → b + b̄) are computed using the current algebra formulation of radiative corrections. This framework allows one to easily enforce the relevant Ward identity that greatly simplifies the calculations. As a result, the one-loop O(α mt m2 W ) contribution is computed through the investigation of only two convergent dia...

A method to calculate two-loop self-energy diagrams of the Standard Model is demonstrated. A direct physical application is the calculation of the two-loop electroweak contribution to the anomalous magnetic moment of the muon 1 2 (g − 2) µ. Presently, we confine ourselves to a " toy " model with only µ, γ and a heavy neutral scalar particle (Higgs). The algorithm is implemented as a FORM-based ...

We study the gauged U(1)B−L extensions of the models for neutrino masses and dark matter. In this class of models, tiny neutrino masses are radiatively induced through the loop diagrams, while the origin of the dark matter stability is guaranteed by the remnant of the gauge symmetry. Depending on how the lepton number is violated in the neutrino mass diagrams, these models are systematically cl...

We calculate supersymmetric two-loop corrections to the anomalous magnetic moment of the muon, consisting of diagrams with a closed scalar fermion or fermion loop and gauge and/or Higgs boson exchange. We discuss the numerical impact of each subclass of diagrams and determine the leading contributions. We analyze in detail constraints from experimental information on the Higgs boson mass, ∆ρ, a...

We discuss a relation between two-loop bosonic worldline Green functions which are obtained by Schmidt and Schubert in two different parametrizations of a twoloop worldline. These Green functions are transformed into each other by some transformation rules based on reparametrizations of the proper time and worldline modular parameters. 1 Fellow of the Danish Research Academy, [email protected]...

We consider a two-loop contribution of Higgs-mediated penguin diagram to B(Bs → μ+μ−) at large tanβ in the MSSM, motivated by a recently proposed two-loop magnetic penguin diagrams by Chen and Geng [1]. Typically the two-loop diagram is a αs correction to the one-loop contributions. However the new contribution can dominate one-loop contributions in a region of parameter space where μ, At and A...

We present results for one-loop matching coefficients between continuum fourfermion operators, defined in the Naive Dimensional Regularization scheme, and staggered fermion operators of various types. We calculate diagrams involving gluon exchange between quark lines, and “penguin” diagrams containing quark loops. For the former we use Landau gauge operators, with and without O(a) improvement, ...

In a recent paper [1] we have presented an automated subtraction method for divergent multi-loop/leg integrals in dimensional regularisation which allows for their numerical evaluation, and applied it to diagrams with massless internal lines. Here we show how to extend this algorithm to Feynman diagrams with massive propagators and arbitrary propagator powers. As applications, we present numeri...