Phenomenological analysis of the Two Higgs Doublet Model

The Two Higgs Doublet model and its phenomenological implications are discussed. A brief survey on the present status of this model is given. In particular, we concentrate on the Two Higgs Doublet Model with Flavor Changing Neutral Currents. First, we develop some new parametrizations of the 2HDM type III, in such a way that the relation of it with models type I and type II become apparent. Based on this parametrization we get some bounds on the mixing vertex involving the second and third lepton generations, and lower bounds on the mass of the pseudoscalar Higgs boson. Further, by using a parametrization in which one of the vacuum expectation values vanishes, we constrain some lepton flavor violating vertices, based on the $g-2 $muon factor and some lepton flavor violating decays. Moreover, upper limits on the decay widths of $\tau \to e\gamma, $and $\tau \to eee $are calculated, finding them to stay far from the reach of near future experiments. On the other hand, as an addendum to this work, we study the production and decays of top squarks at the Tevatron collider in models of low-energy supersymmetry breaking. We consider that the lightest Standard Model superpartner is a light neutralino that predominantly decays into a photon and a light gravitino, and that the lighter stop is the next-to-lightest Standard Model superpartner. For a modest projection of the final Tevatron luminosity, $L\simeq 4$ fb$^{-1}$, stop masses of order 300 GeV are accessible. We also consider the production and decay of ten degenerate squarks, and we find that common squark masses up to 360 GeV are easily accessible, and that the reach increases further if the gluino is light