Automatized calculation of 2-fermion production with DIANA and aITALC

The family of two fermion final states is among the cleanest final states at the International Linear Collider (ILC) project. The package aITALC has been developed for a calculation of their production cross sections, and we present here benchmark numerical results in one loop approximation in the electroweak Standard Model. We are using packages like QGRAF, DIANA, FORM, LOOPTOOLS for intermediate steps.Comment: Contribution to the proceedings of the International Conference on Linear Colliders (LCWS 04), Paris, April 19-23, 2004. 5 pages, 1 figure, 5 table

Elektroweak one-loop corrections for e^+e^- annihilation into t\bar{t} including hard bremsstrahlung

We present the complete electroweak one-loop corrections to top-pair production at a linear e^+e^- collider in the continuum region. Besides weak and photonic virtual corrections, real hard bremsstrahlung with simple realistic kinematical cuts is included. For the bremsstrahlung we advocate a semi-analytical approach with a high numerical accuracy. The virtual corrections are parametrized through six independent form factors, suitable for Monte-Carlo implementation. Alternatively, our numerical package topfit, a stand-alone code, can be utilized for the calculation of both differential and integrated cross sections as well as forward--backward asymmetries.Comment: 34 page

Status of Electroweak Corrections to Top Pair Production

We review the status of electroweak radiative corrections to top-pair production at a Linear Collider well above the production threshold. We describe the Fortran package topfit and present numerical results at sqrt(s) = 500 GeV, 1 TeV, and 3 TeV.Comment: 6 pages, LaTex, 2 tables, 1 figure, talk presented by T.R. at the Int. Workshop on Linear Colliders (LCWS 2002), 26-30 Aug 2002, Jeju Island, Kore

MS vs. Pole Masses of Gauge Bosons: Electroweak Bosonic Two-Loop Corrections

The relationship between MS and pole masses of the vector bosons Z and W is calculated at the two-loop level in the Standard Model. We only consider the purely bosonic contributions which represents a gauge invariant subclass of diagrams. All calculations were performed in the linear $R_\xi$ gauge with three arbitrary gauge parameters utilizing the method of asymptotic expansions. The results are presented in analytic form as series in the small parameters $\sin^2\theta_W$ and mass ratio $m_Z^2/m_H^2$. As a byproduct we obtain the bosonic two-loop contributions to the renormalization of the weak mixing parameter $\sin^2\theta_W$ and of the Fermi constant. The running of Fermi constant will become important at high energy colliders.Comment: LaTeX, 36 p., 10 fig.; in v3 more technical details about renormalization procedure are adde

End-of-life decisions and the law: a new law for South Africa?

No Abstract

Massive two-loop Bhabha scattering -- the factorizable subset

The experimental precision that will be reached at the next generation of colliders makes it indispensable to improve theoretical predictions significantly. Bhabha scattering (e^+ e^- \to e^+ e^-) is one of the prime processes calling for a better theoretical precision, in particular for non-zero electron masses. We present a first subset of the full two-loop calculation, namely the factorizable subset. Our calculation is based on DIANA. We reduce tensor integrals to scalar integrals in shifted (increased) dimensions and additional powers of various propagators, so-called dots-on-lines. Recurrence relations remove those dots-on-lines as well as genuine dots-on-lines (originating from mass renormalization) and reduce the dimension of the integrals to the generic d = 4 - 2 \epsilon dimensions. The resulting master integrals have to be expanded to ${\it O}(\epsilon)$ to ensure proper treatment of all finite terms.Comment: 5 pages, Talk presented by A.W. at RADCOR and Loops and Legs 2002 in Banz, Germany, to appear in the proceeding

Complete electroweak one-loop radiative corrections to top-pair production at TESLA -- a comparison

Electroweak one-loop radiative corrections to the process e^+ e^- -> t tbar are revisited. Two groups from Karlsruhe and Bielefeld/Zeuthen performed independent calculations of both (virtual and soft) QED contributions and weak virtual corrections. For the angular distribution an agreement of at least eight digits for the weak corrections and of at least seven digits for additional photonic corrections is established.Comment: 12 pages, minor improvement of soft photon correction

On the tensor reduction of one-loop pentagons and hexagons

We perform analytical reductions of one-loop tensor integrals with 5 and 6 legs to scalar master integrals. They are based on the use of recurrence relations connecting integrals in different space-time dimensions. The reductions are expressed in a compact form in terms of signed minors, and have been implemented in a mathematica package called hexagon.m. We present several numerical examples.Comment: Latex, 7 pages, 2 eps figures. Contribution to the proceedings of `Loops and Legs in Quantum Field Theory', April 2008, Sondershausen, German