Higgs-boson production in association with W or Z bosons, pp →WH/ZHϩX, is the most promising discovery channel for a light standard model Higgs particle at the Fermilab Tevatron. We present the calculation of the electroweak O(␣) corrections to these processes. The corrections decrease the theoretical prediction by up to 5%-10%, depending in detail on the Higgs-boson mass and the input-parameter scheme. We update the cross-section prediction for associated WH and ZH production at the Tevatron and at the CERN LHC, including the next-to-leading order electroweak and QCD corrections, and study the theoretical uncertainties induced by factorization and renormalization scale dependences and by the parton distribution functions.

Pair production of W bosons constitutes an important background to Higgs boson and new physics searches at the Large Hadron Collider LHC. We have calculated the loop-induced gluon-fusion process gg → W * W * → leptons, including intermediate light and heavy quarks and allowing for arbitrary invariant masses of the W bosons. While formally of next-to-next-to-leading order, the gg → W * W * → leptons process is enhanced by the large gluon flux at the LHC and by experimental Higgs search cuts, and increases the next-to-leading order W W background estimate for Higgs searches by about 30%. We have extended our previous calculation to include the contribution from the intermediate topbottom massive quark loop and the Higgs signal process. We provide updated results for cross sections and differential distributions and study the interference between the different gluon scattering contributions. We describe important analytical and numerical aspects of our calculation and present the public GG2WW event generator.

The radiative corrections of the strong and electroweak interactions are calculated at next-to-leading order for Higgs-boson production in the weak-boson-fusion channel at hadron colliders. Specifically, the calculation includes all weak-boson fusion and quark-antiquark annihilation diagrams to Higgs-boson production in association with two hard jets, including all corresponding interferences. The results on the QCD corrections confirm that previously made approximations of neglecting s-channel diagrams and interferences are well suited for predictions of Higgs production with dedicated vector-boson fusion cuts at the LHC. The electroweak corrections, which also include real corrections from incoming photons and leading heavy Higgs-boson effects at two-loop order, are of the same size as the QCD corrections, viz. typically at the level of 5%-10% for a Higgs-boson mass up to 700 GeV. In general, both types of corrections do not simply rescale differential distributions, but induce distortions at the level of 10%. The discussed corrections have been implemented in a flexible Monte Carlo event generator.

Radiative corrections of strong and electroweak interactions are presented at next-to-leading order for the production of a Higgs boson plus two hard jets via weak interactions at the CERN Large Hadron Collider. The calculation includes all weak-boson fusion and quark-antiquark annihilation diagrams as well as the corresponding interferences. The electroweak corrections, which are discussed here for the first time, reduce the cross sections by 5% and thus are of the same order of magnitude as the QCD corrections.

Vector-boson pair production is an important background for Higgs boson and new physics searches at the Large Hadron Collider LHC. We have calculated the loop-induced gluon-fusion process gg → W W → leptons, allowing for arbitrary invariant masses of the intermediate W bosons. This process contributes at O(α 2 s ) relative to quarkantiquark annihilation, but its importance is enhanced by the large gluon flux at the LHC and by experimental cuts employed in Higgs boson searches. We find that gg → W W provides only a moderate correction (ca. 5%) to the inclusive W -pair production cross section at the LHC. However, after taking into account realistic experimental cuts, the gluon-fusion process becomes significant and increases the theoretical W W background estimate for Higgs searches in the pp → H → W W → leptons channel by approximately 30%.