NNLO massive corrections to Bhabha scattering and theoretical precision of BabaYaga@NLO

We provide an exact calculation of next-to-next-to-leading order (NNLO) massive corrections to Bhabha scattering in QED, relevant for precision luminosity monitoring at meson factories. Using realistic reference event selections, exact numerical results for leptonic and hadronic corrections are given and compared with the corresponding approximate predictions of the event generator BabaYaga@NLO. It is shown that the NNLO massive corrections are necessary for luminosity measurements with per mille precision. At the same time they are found to be well accounted for in the generator at an accuracy level below the one per mille. An update of the total theoretical precision of BabaYaga@NLO is presented and possible directions for a further error reduction are sketched.Comment: 5 pages, 3 tables, contrib. to proceedings of International Workshop on e+e- collisions: from Phi to Psi, PHIPSI11, BINP, Novosibirsk, Russia, September 19-22, 201

Planar two-loop master integrals for massive Bhabha scattering: N_f=1 and N_f=2

Recent developments in the computation of two-loop master integrals for massive Bhabha scattering are briefly reviewed. We apply a method based on expansions of exact Mellin-Barnes representations and evaluate all planar four-point master integrals in the approximation of small electron mass at fixed scattering angle for the one-flavor case. The same technique is employed to derive and evaluate also all two-loop masters generated by additional fermion flavors. The approximation is sufficient for the determination of QED two-loop corrections for Bhabha scattering in the kinematics planned to be used for the luminosity determination at the ILC.Comment: 10 pages, 3 figures, 1 table, to appear in the proceedings of 8th DESY Workshop on Elementary Particle Theory: Loops and Legs in Quantum Field Theory, Eisenach, Germany, 23-28 Apr 2006; eqns. 22 and 23 correcte

NNLO Computational Techniques: the Cases H -> gamma gamma and H -> g g

A large set of techniques needed to compute decay rates at the two-loop level are derived and systematized. The main emphasis of the paper is on the two Standard Model decays H -> gamma gamma and H -> g g. The techniques, however, have a much wider range of application: they give practical examples of general rules for two-loop renormalization; they introduce simple recipes for handling internal unstable particles in two-loop processes; they illustrate simple procedures for the extraction of collinear logarithms from the amplitude. The latter is particularly relevant to show cancellations, e.g. cancellation of collinear divergencies. Furthermore, the paper deals with the proper treatment of non-enhanced two-loop QCD and electroweak contributions to different physical (pseudo-)observables, showing how they can be transformed in a way that allows for a stable numerical integration. Numerical results for the two-loop percentage corrections to H -> gamma gamma, g g are presented and discussed. When applied to the process pp -> gg + X -> H + X, the results show that the electroweak scaling factor for the cross section is between -4 % and + 6 % in the range 100 GeV < Mh < 500 GeV, without incongruent large effects around the physical electroweak thresholds, thereby showing that only a complete implementation of the computational scheme keeps two-loop corrections under control.Comment: LaTeX, 70 pages, 8 eps figure

Two-Loop Threshold Singularities, Unstable Particles and Complex Masses

The effect of threshold singularities induced by unstable particles on two-loop observables is investigated and it is shown how to cure them working in the complex-mass scheme. The impact on radiative corrections around thresholds is thoroughly analyzed and shown to be relevant for two selected LHC and ILC applications: Higgs production via gluon fusion and decay into two photons at two loops in the Standard Model. Concerning Higgs production, it is essential to understand possible sources of large corrections in addition to the well-known QCD effects. It is shown that NLO electroweak corrections can incongruently reach a 10 % level around the WW vector-boson threshold without a complete implementation of the complex-mass scheme in the two-loop calculation.Comment: LaTeX, 12 pages, 7 figure

Argentina y Brasil: Hacia una Alianza Estratégica… con China

El presente artículo analiza la relación bilateral entre Brasil y Argentina a la luz de los vínculos que ambos países viene construyendo con la República Popular de China. Se sostiene que la profundización de las interacciones con el país asiático afectan la alianza estratégica que Brasil y Argentina construyeron en la primera década del siglo XXIFil: Actis, Esteban. Universidad Nacional de Rosario. Facultad de Ciencias Politicas y Relaciones Internacionales. Instituto de Investigaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

The bilateral relationship between Argentina and Brazil (2011-2014): The confluence of domestic and systemic factors for a lower relative intensity in the interactions

El presente trabajo tiene como objetivo analizar la dinámica del vínculo bilateral entre Argentina y Brasil entre los años 2011-2014, recorte que coincide con el traspaso del mando presidencial de “Lula” Da Silva a Dilma Rousseff. A partir de la selección de ciertos indicadores, la evidencia señala que la relación estuvo signada por una menor intensidad relativa, tanto en las interacciones económicas como políticas. Para explicar dicho fenómeno se optó por indagar en un conjunto de factores propios del sistema internacional como elementos domésticos de cada una de las unidades estatales analizadas.This study aims to analyze the dynamics of the bilateral relation among Argentina and Brazil between the years 2011-2014, period of time that coincides with the assumption of President Dilma Rousseff. The facts indicate that the relationship was characterized for a moment of lower relative intensity, both in the economic and politics interactions. To explain such phenomenon we opted to dig and interrelated a set of systemic and domestics factors in both countries.Fil: Actis, Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Políticas y Relaciones Internacionales. Instituto de Investigaciones; Argentin