| Even though the Standard Model has been very successful in describing almost all of the experimental data in high energy physics, it is widely believed that a new physics theory will occur at TeV scale. Motivated by the "Little Hierarchy problem", Little Higgs models were proposed. In Little Higgs models, the Higgs boson is a pseudo-Nambu-Goldstone boson, and its mass is protected by enough symmetries so that no tree level mass term exists. Two or more couplings in the effective Lagrangian are needed to break these symmetries and generate the Higgs boson mass at the one-loop level, which is called the "collective symmetry breaking" mechanism. The quadratically divergent corrections to the Higgs boson mass are neatly canceled at one-loop level: the corrections from the top quark loop is canceled by a new heavy quark and the corrections from the Standard Model gauge bosons are canceled by a set of new gauge bosons. With T-parity, the mass scale of the Little Higgs models is allowed to be less than one TeV by the precision electroweak tests due to the absence of mixings between the new gauge bosons and the Standard Model gauge bosons. Furthermore, Little Higgs model with T-parity also predicts a dark matter candidate and leads to the very interesting collider phenomenology that is different from the Standard Model prediction.;In this work, I investigate top quark physics and Higgs boson physics in the Littlest Higgs model with T-parity at the Large Hadron Collider (LHC) at CERN. The effects through the virtual appearance of the new particles have a large impact on the Higgs boson production total cross section via the gluon-gluon fusion process and decay branching ratios. For the top quark physics, since the wtb coupling is modified at the tree level due to the mixings between the top quark and a T-even heavy quark, the single-top quark production cross sections will be reduced, as compared to Standard Model predictions. I also present the one-loop electroweak corrections to the gtt¯ coupling, which leads to an anomalous coupling written in terms of several form factors. And I further examine the effects in the top quark pair production via the quark annihilation process at the LHC. The negative corrections from the Standard Model particle loops are partially canceled by the positive contributions from the loops of the new heavy particles, and the latter dominates in the large invariant mass of the top quark pair.;I also investigate the collider signatures of the new particles in the Littlest Higgs model with T-parity at the LHC and a Linear Collider (LC). I show the total cross sections, the typical decay branching ratios of the new particles and estimate the event rates for some interesting signatures at the LHC. Since the mass of the heavy gauge boson only depends on the symmetry breaking scale of the model, I study in detail the heavy gauge boson pair production at both the LHC and the LC, including the backgrounds from the Standard Model. By using a charged lepton pair with large missing energy signature at the LHC, the discovery potential of the heavy gauge boson pair production could reach a 5sigma statistical significance. However, it is difficult to reconstruct the mass of the heavy gauge boson at the LHC. By using the four jets with missing energy signature at the LC, both mass and spin of the heavy gauge boson could be determined. It is also possible to distinguish different models at the LC by using the spin correlations. |
