A. Vicini

Two loop electroweak top corrections: Are they under control?

Abstract The top quark contribution to two-loop, purely electroweak radiative corrections is investigated in the case of the ϱ parameter, extracted from the ratio of neutral to charged current amplitudes in low-energy neutrino-lepton scattering. It is shown that the order O ( G μ 2 m t 2 m z 2 ) contribution is numerically comparable and shares the same sign with the leading O ( G μ 2 m t 4 ) term, for realistic values of the top and Higgs masses. The result raises doubts on the reliability of the heavy top approximation in the two-loop contributions to electroweak observables. A naive extrapolation of this result to LEP observables would suggest an overall two-loop electroweak contribution close to the ultimate experimental sensitivity.

The gluon-fusion process

This Report summarises the results of the second years activities of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. The first working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) focuses on predictions (central values and errors) for total Higgs production cross sections and Higgs branching ratios in the Standard Model and its minimal supersymmetric extension, covering also related issues such as Monte Carlo generators, parton distribution functions, and pseudo-observables. This second Report represents the next natural step towards realistic predictions upon providing results on cross sections with benchmark cuts, differential distributions, details of specific decay channels, and further recent developments.