S. Dittmaier

Higgs radiation off top quarks at the Tevatron and the LHC.

Higgs bosons can be searched for in the channels pp macro/pp-->tt macro H + X at the Fermilab Tevatron and the Cern Large Hadron Collider (LHC). We have calculated the QCD corrections to these processes in the standard model at next-to-leading order. The higher-order corrections reduce the renormalization and factorization scale dependence considerably and stabilize the theoretical predictions for the cross sections. At the central scale mu = (2m(t)+M(H))/2 the properly defined K factors are slightly below unity for the Tevatron (K approximately 0.8) and slightly above unity for the LHC (K approximately 1.2).

NLO QCD corrections to t anti-t H production in hadron collisions

The Higgs boson H of the Standard Model can be searched for in the channels p pbar / pp -> t tbar H + X at the Tevatron and the LHC. The cross sections for these processes and the final-state distributions of the Higgs boson and top quarks are presented at next-to-leading order QCD. To calculate these QCD corrections, a special calculational technique for pentagon diagrams has been developed and the dipole subtraction formalism has been adopted for massive particles. The impact of the corrections on the total cross sections is characterized by K factors, the ratios of the cross sections in next-to-leading order over leading order QCD. At the central scale mu_0 = (2 m_t + M_H)/2 the K factors are found to be slightly below unity for the Tevatron (K sim 0.8) and slightly above unity for the LHC (K sim 1.2). Including the corrections significantly stabilizes the theoretical predictions for total cross sections and for the distributions in rapidity and transverse momentum of the Higgs boson and top quarks.The Higgs boson H of the Standard Model can be searched for in the channels p pbar / pp ->t tbar H + X at the Tevatron and the LHC. The cross sections for these processes and the final-state distributions of the Higgs boson and top quarks are presented at next-to-leading order QCD. To calculate these QCD corrections, a special calculational technique for pentagon diagrams has been developed and the dipole subtraction formalism has been adopted for massive particles. The impact of the corrections on the total cross sections is characterized by K factors, the ratios of the cross sections in next-to-leading order over leading order QCD. At the central scale mu_0 = (2 m_t + M_H)/2 the K factors are found to be slightly below unity for the Tevatron (K sim 0.8) and slightly above unity for the LHC (K sim 1.2). Including the corrections significantly stabilizes the theoretical predictions for total cross sections and for the distributions in rapidity and transverse momentum of the Higgs boson and top quarks.

Neutral Higgs boson pair production at hadron colliders: QCD corrections

Neutral Higgs-boson pair production provides the possibility of studying the trilinear Higgs couplings at future high-energy colliders. We present the QCD corrections to the gluon-initiated processes in the limit of a heavy top quark in the loops and the Drell-Yan-like pair production of scalar and pseudoscalar Higgs particles. The pp cross sections are discussed for LHC energies within the Standard Model and its minimal supersymmetric extension. The QCD corrections are large, enhancing the total cross sections significantly.

NLO QCD corrections to t anti-t + jet production at hadron colliders

We report on the calculation of the next-to-leading order QCD corrections to the production of top--anti-top quark pairs in association with a hard jet at the Tevatron and at the LHC. We present results for the t tbar + jet cross section and the forward--backward charge asymmetry. The corrections stabilize the leading-order prediction for the cross section. The charge asymmetry receives large corrections.

Weyl-van der Waerden formalism for helicity amplitudes of massive particles

The Weyl--van der Waerden spinor technique for calculating helicity amplitudes of massive and massless particles is presented in a form that is particularly well suited to a direct implementation in computer algebra. Moreover, we explain how to exploit discrete symmetries and how to avoid unphysical poles in amplitudes in practice. The efficiency of the formalism is demonstrated by giving explicit compact results for the helicity amplitudes of the processes

Next-to-Leading-Order QCD Corrections toWW+JetProduction at Hadron Colliders

ensuremath{gamma}stackrel{ensuremath{rightarrow}}{ensuremath{gamma}}foverline{f},

Radiative corrections to

foverline{f}ensuremath{rightarrow}ensuremath{gamma}ensuremath{gamma}ensuremath{gamma},

in the electroweak standard model

{ensuremath{mu}}^{ensuremath{-}}{ensuremath{mu}}^{+}ensuremath{rightarrow}foverline{f}ensuremath{gamma}.