| The Standard Model (SM), which was established in the late 1960s, has been tested to be successful in describing the strong and electroweak interactions between the fundamental particles. However, the SM still has some fundamental problems (e.g. gauge hierarchy prob-lem, neutrino masses and dark matter etc). It is commonly believed that the SM can only be the low energy effective theory of a fundamental theory and there should exist new physics (NP) near the TeV scale. The twin Higgs mechanism has recently been proposed to solve the little hierarchy problem. Left-right twin Higgs (LRTH) model is a concrete implementation of the twin Higgs mechanism in left-right models. Besides the SM-like Higgs boson. this model also predicts the existences of the heavy vector-like T-quark, the heavy gauge bosons, the neutral and charged scalars, which can generate the typical signatures at the high energy collider experiments.With the successful operation of the large hadron collider (LHC) at the CERN, the particle physics research has entered into the new era of "TeV scale". In July of 2012, ATLAS and CMS Collaborations together claimed the discovery of a new particle, the SM-like Higgs boson with mass about 125 GeV. The data of the LHC run-1 show that the properties of this new particle arc relatively close to the SM Higgs. However, such Higgs-like resonance can also be well explained in many NP models. Thus, to measure the properties of the Higgs boson precisely is very important to test the SM and distinguish the various NP models. Compared with the LHC, the striking features of the proposed high-energy e+ e-linear colliders, or the Higgs factory in other words, are its much more clean background and higher accuracy of measurements. Therefore, the high-energy linear colliders can carry out more detailed studies of the new discoveries at LHC.In this thesis, we focus on the phenomenology of the LRTH model at the LHC and the possible high-energy e+e- linear colliders. Our works are as follows:(1) We studied the Higgs decay channels in the LRTH model. especially the signal strength of the diphoton decay channel. By using the LHC Higgs data from both ATLAS and CMS, we also performed a global fit to the parameter space in the LRTH model. Due to the decoupling effect, the signal rates normalized to the SM prediction for the five Higgs search channels are always suppressed when new physics contributions are taken into account and the scale parameter f<550 GeV is excluded at 95% confidence level from the experimental viewpoint.(2) We studied the production and decays of a light pseudoscalar boson Φ0 with m≤mh/2, and explored its phenomenological consequences when the latest LHC Higgs data are taken into account.The future e+e- collider with (?)=250 GeV,the processes e+e-â†' Zhâ†'Z(Φ0Φ0)â†'Z(4b,2b2Ï„)are promising for discovering such a light pseudoscalar Φ0.(3) We examined the status of a light dark matter S under the currently available experimen-tal constraints including the latest LHC Higgs data, the XENON 100 and LUX limit on the dark matter scattering off the nucleon. The numerical results show that, the global fits to the latest LHC and Tevatron Higgs data provide a strong constraint:Brinv<20% at 2σ level; On the other hand, the LUX can give more constraints on the coupling parameter ghss.(4) We made a systematic investigation for the single and pair production of the heavy T quark through the processes:e+e-â†'tT+Tt and TT, the neutral scalar associate productions e+e- â†'tTh+Tth, TTh,tTΦ0+TtΦ0 and TTΦ0. We calculated the production cross sections and made some phenomenological analysis.(5) We analyzed three dominant single SM-like Higgs boson production processes in the LRTH model:e+e- â†' Zh, e+e- â†' vvh and e+e- â†' tth for three possible energy stages of the ILC, and compared our results with the expected experimental accuracies for various accessible Higgs decay channels. For the case of ILC-250 (1000) GeV,for example,the lower limit is f>1150 (1400) GeV at the 2σ level. |
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