Top Squark Effects on Higgs Boson Production and Decays at the LHC

In the Minimal Supersymmetric Standard Model, one of the scalar top quarks can be relatively light and its couplings to Higgs bosons strongly enhanced. I will discuss two consequences of this feature: 1) the effects of scalar top loops on the main production mechanism of the lightest Higgs boson at the LHC, the gluon-fusion mechanism $gg \to h$, and on the important decay channel into two photons $h \to \gamma \gamma$; and 2) the production of the light Higgs particle in association with top-squark pairs at proton colliders, $pp \to \tilde{t}_1 \tilde{t}_1 h$.