Phenomenological Study Of The Production Processes Of Higgs Bosons Near 125 GeV In The New Physics Models

The Standard Model (SM) can describe all the visible matter in the Universe in terms of a limited number of fermionic constituents of matter, including six quarks, three charged leptons and three light neutrinos. It also can comprise three fundamental gauge interactions (the electromagnetic, strong and weak forces) between these constituents. The Standard Model is in good agreement with almost confirmed experimental results from all kinds of particle accelerators.The Large Hadron Collider (LHC) was built to explore the mechanism of electroweak symmetry breaking (EWSB) at the TeV energy scale and shed light on physics beyond the SM of electroweak and strong interactions. The discovery in July 2012 of the Higgs boson with a mass about 125 GeV by the ATLAS and CMS collaborations at the Large Hadron Collider indicates the great success of the Standard Model and marks a new progress in modern particle physics. It is a first triumph for the LHC physics program.However, while this discovery completes our picture of the SM, it still leaves many important questions open. In particular, the SM does not explain the value of the electroweak (EW) scale itself. And, there is the closely related issue of understanding why the Higgs boson is so light.Indeed the Higgs data analyses of the ATLAS and CMS collaborations are beginning to provide a comprehensive picture of the production and decay properties of the 125 GeV Higgs boson. The measurements of the Higgs properties may provide a guide as to where and how to look for this New Physics. The Higgs data and their interpretation currently provide the impor-tant guidelines for New Physics beyond the SM (BSM) theories. Consequently, in-depth studies of the Higgs signal could have profound implications for supersymmetric models, Manohar-Wise model, little Higgs models and so on.In this thesis, some production processes of higgs bosons near 125 Gev in the new physics models are studied, including:(1) We assume a SM-like Higgs with the mass 123-127 GeV and study its implication in low energy SUSY by comparing the MSSM and NMSSM. We consider various experimental constraints at 2σ level (including the muon g - 2 and the dark matter relic density) and perform a comprehensive scan over the parameter space of each model. Then in the parameter space which is allowed by current-experimental constraints and also predicts a SM-like Higgs in 123-127 GeV, we examine the properties of the sensitive parameters (like the top squark mass and the trilinear coupling At) and calculate the rates of the di-photon signal and the VV* (V= W, Z) signals at the LHC. Our typical findings are:(ⅰ) In the MSSM the top squark and At must be large and thus incur some fine-tuning, which can be much ameliorated in the NMSSM; (ⅱ) In the MSSM a light stau is needed to enhance the di-photon rate of the SM-like Higgs to exceed its SM prediction, while in the NMSSM the di-photon rate can be readily enhanced in several ways; (ⅲ) In the MSSM the signal rates of pp → h → VV* at the LHC are never enhanced compared with their SM predictions, while in the NMSSM they may get enhanced significantly; (ⅳ) A large part of the parameter space so far survived will be soon covered by the expected XENON100(2012) sensitivity (especially for the NMSSM).(2) We study the Higgs pair production at the LHC in the Manohar-Wise model, which extends the SM by one family of color-octet and isospin-doublet scalars. We first scanned over the parameter space of the Manohar-Wise model considering exprimental constraints and performed fits in the model to the latest Higgs data by using the ATLAS and CMS data separately. Then we calculated the Higgs pair production rate and investigated the potential of its discovery at the LHC14. We conclude that:(ⅰ) Under current constrains including Higgs data after Run I of the LHC, the cross section of Higgs pair production in the Manohar-Wise model can be enhanced up to even 103 times prediction in the SM. (ⅱ) Moreover, the sizable enhancement comes from the contributions of the, CP-odd color-octet scalar SAI. For lighter scalar SAI and larger values of|λI|, the cross section of Higgs pair production can be much larger. (ⅲ) After running again of LHC at 14 TeV, most of the parameter spaces in the Manohar-Wise model can be test. For an integrated luminosity of 100 fb-1 at the LHC14, when the normalized ratio R= 10, the process of Higgs pair production can be detected.(3) In the framework of the LHT model, we investigate the s-channel and W-associated productions of Higgs plus single top at the 8 TeV and 14 TeV LHC. In the allowed parameter space, we find the relative corrections of pp → tHb at the 8 TeV and 14 TeV LHC can reach-25% and -23%, and the relative corrections of pp → tHW-can reach-25% and -20% at 2σ level, respectively. These relative corrections are significant so that the LHT effect may be detected at the future LHC.