Fawzi Boudjema

b anti-b Higgs production at the LHC: Yukawa corrections and the leading Landau singularity

At tree-level Higgs production in association with a b-quark pair proceeds through the small Yukawa bottom coupling in the Standard Model. Even in the limit where this coupling vanishes, electroweak one-loop effects, through the top-Higgs Yukawa coupling in particular, can still trigger this reaction. This contribution is small for Higgs masses around 120GeV but it quickly picks up for higher Higgs masses especially because the one-loop amplitude develops a leading Landau singularity and new thresholds open up. These effects can be viewed as the production of a pair of top quarks which rescatter to give rise to Higgs production through WW fusion. We study the leading Landau singularity in detail. Since this singularity is not integrable when the one-loop amplitude is squared, we regulate the cross section by taking into account the width of the internal top and W particles. This requires that we extend the usual box one-loop function to the case of imaginary masses. We show how this can be implemented analytically in our case. We study in some detail the cross section at the LHC as a function of the Higgs mass and show how some distributions can be drastically affected compared to the tree-level result.

Leading Yukawa corrections to Higgs production associated with a tagged bottom-antibottom pair in the standard model at the CERN LHC

Considering the large value of the top Yukawa coupling, we investigate the leading one-loop Yukawa electroweak corrections that can be induced by the top quark in a process such as Higgs production in association with a tagged bottom-antibottom pair at the LHC. At next-to-leading order these contributions are found to be small at the LHC both for the total cross section and for the distributions. In the limit of vanishing bottom Yukawa coupling where the leading order contribution vanishes, the process can still be induced at one-loop through the top quark transition. Though this contribution which can be counted as part of the next-to-next-to-leading order correction is small for Higgs masses around 120 GeV, it quickly picks up for higher Higgs masses. This contribution represents the rescattering of the top quarks and their decay into Ws leading to Higgs production through WW fusion.

Next-to-leading order corrections to e + e − → W + W − Z and e + e − → Z Z Z

We calculate the one-loop electroweak corrections to e+e- to WWZ and e+e- to ZZZ and analyse their impacts on both the total cross section and some key distributions. These processes are important for the measurements of the quartic couplings of the massive gauge bosons which can be a window on the mechanism of spontaneous symmetry breaking. We find that even after subtracting the leading QED corrections, the electroweak corrections can still be large especially as the energy increases. We compare and implement different methods of dealing with potential instabilities in the routines pertaining to the loop integrals. For the real corrections we apply a dipole subtraction formalism and compare it to a phase-space slicing method.

NLO corrections to e+e- to WWZ and e+e- to ZZZ

We calculate the one-loop electroweak corrections to e+e- to WWZ and e+e- to ZZZ and analyse their impacts on both the total cross section and some key distributions. These processes are important for the measurements of the quartic couplings of the massive gauge bosons which can be a window on the mechanism of spontaneous symmetry breaking. We find that even after subtracting the leading QED corrections, the electroweak corrections can still be large especially as the energy increases. We compare and implement different methods of dealing with potential instabilities in the routines pertaining to the loop integrals. For the real corrections we apply a dipole subtraction formalism and compare it to a phase-space slicing method.

One-loop electroweak and QCD corrections to vector boson scattering into top pairs and application to the ILC

We calculate the electroweak and QCD corrections to

NLO corrections to e+e- ---> WWZ and e+e- ---> ZZZ

{W}^{ensuremath{-}}{W}^{+}ensuremath{rightarrow}toverline{t}

Electroweak corrections to W+W-Z and ZZZ production at the linear collider†

and

Next-to-leading order corrections to e{sup +}e{sup -{yields}}W{sup +}W{sup -}Z and e{sup +}e{sup -{yields}}ZZZ

ZZensuremath{rightarrow}toverline{t}

Next-to-leading order corrections toe+e−→W+W−Zande+e−→ZZZ

. We also consider the interplay of these corrections with the effect of anomalous interactions that affect the massive weak bosons and the top. The results at the

BbH production at the CERN LHC : Yukawa corrections and the leading Landau singularity

VV