  We calculate the leading electroweak (EW) corrections to the important
process of Higgs production associated with two bottom quarks at the CERN Large
Hadron Collider (LHC). Our study is restricted to the Standard Model (SM).
  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, EW 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. An important part of the thesis is
devoted to the topic of Landau singularities in one-loop Feynman diagrams and
application to the specific process of bbH production at the LHC.
  Since the 4-point leading Landau 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 complex 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.
