Recent studies of QCD and MSSM processes are discussed. These processes are handled with the GRACE system, which is a package of the automatic calculation of the amplitude based on the standard model (SM) and the minimal supersymmetric extension of the standard model (MSSM), are discussed. In order to evaluate multi-loop diagrams, we have developed the direct computation method (DCM). As an app...

In this work we calculate two two-loop massless Feynman integrals pertaining to self-energy diagrams using NDIM (Negative Dimensional Integration Method). We show that the answer we get is 36-fold degenerate. We then consider special cases of exponents for propagators and the outcoming results compared with known ones obtained via traditional methods. PACS numbers: 02.90+p, 03.70+k, 12.38.Bx Sh...

A method of Feynman diagrams summation, based on using Schwinger-Dyson equations and Ward identities, is verified by calculating some four-loop diagrams in N = 1 supersymmetric electrodynamics, regularized by higher derivatives. In particular, for the considered diagrams correctness of an additional identity for Green functions, which is not reduced to the gauge Ward identity, is proved.

Abstract: We compute one loop neutrino masses in the R-parity violating Minimal Supersymmetric Model, including the bilinear Rp / masses in the mass insertion approximation. To the order we calculate, our results are independent of the Higgs-lepton basis choice. We have a variety of perturbative parameters—gauge, yukawa and trilinear couplings, and Rp violating masses. Their relative magnitudes...

We derive the renormalization group equations for a generic nonrenormalizable theory. We show that the equations allow one to derive the structure of the leading divergences at any loop order in terms of one-loop diagrams only. In chiral perturbation theory, e.g., this means that one can obtain the series of leading chiral logs by calculating only one loop diagrams. We discuss also the renormal...

We present the full one-loop calculation for gg ! ZZ in the Minimal Supersymmetric Model (MSSM) including nonresonant contributions from the squark loop diagrams and provide analytical expressions for the helicity amplitudes. The one-loop process gg ! ZZ via quark loops has been calculated in the Standard Model. In supersymmetric models, additional contributions arise from squark loops. In some...

We derive the renormalization group equations for a generic nonrenormalizable theory. We show that the equations allow one to derive the structure of the leading divergences at any loop order in terms of one-loop diagrams only. In chiral perturbation theory, e.g., this means that one can obtain the series of leading chiral logs by calculating only one loop diagrams. We discuss also the renormal...

We illustrated via the sunset diagram that dimensional regularization ’deforms’ the nonlocal contents of multi-loop diagrams with its equivalence to cutoff regularization scheme recovered only after sub-divergence were subtracted. Then we employed a differential equation approach for calculating loop diagrams to verify that dimensional regularization deformed the ’low energy’ contents before su...

A fully numerical method to calculate loop integrals, a numerical contour-integration method, is proposed. Loop integrals can be interpreted as a contour integral in a complex plane for an integrand with multi-poles in the plane. Stable and efficient numerical integrations an along appropriate contour can be performed for tensor integrals as well as for scalar ones appearing in loop calculation...