Precision Study On Heavy Quark And Hz_γProductions At The LHC

Since the data of the LHC runl show that the properties of the new boson discov-ered in2012are relatively close to the standard model(SM) Higgs, the SM gains a great success again. But there are still some theoretical problems with the SM that can not be solved in the SM framework. These problems are strong motivations for particle physi-cists to search for new physics. As one of these problems, the fine-tuning problem of the Higgs boson has become more intriguing after the discovery of the Higgs boson with a mass around126GeV. To regulate quadratically divergent contributions to the Higgs mass, many extended models are proposed. Among them, the littlest Higgs model with T-parity(LHT) deserves attention due to its attractive solution to the fine-tuning prob-lem. Moreover, the heavy photon(AH) predicted in the LHT is a good candidate for dark mater, which is also one of the problems unsolved in current particle physics.The T-odd heavy quark productions are important channles for searching for the LHT signals in experiments. We calculated the single heavy quark production at the (?)s=8TeV and (?)s-14TeV LHC, and same-sign heavy quark pair production at the14TeV LHC, all up to the QCD NLO accuracy. We investigated the dependence of the total cross-sections of the two production processes on renormalization/factorization scale and the two LHT parametes,f and κ. For the same-sign heavy quark pair production, we also discussed the uncertainty from the parton distribution functions(PDFs). The kinematic distributions of the final products from the heavy quark subsequential decays were studied in detail in our work.Obviously, to determine the properties of the Higgs boson precisely is the main task of further experiments. In the SM, some Higgs couplings of the type gHvv> and9HVV’V" are absent at tree level, and they would be particularly sensitive to new physics. The HZγ production at the LHC can offer the possibility to directly investigate the HZγ, HZZγ, HZγγ anomalous Higgs gauge couplings, as they would cause devia- tions from the SM predictions. Due to the importance of this process, we calculated the ppâ†'HZγ+X process with subsequential Higgs and Z-boson decays at the (?)s=14TeV LHC including the NLO QCD corrections, and discussed its possible background.The innovations in this dissertation are listed below:·We studied the heavy quark productions in the LHT at the LHC up to QCD NLO accuracy with subsequent heavy quark decays for the first time. We investigated the final signals and the corresponding SM background. Our results will be a useful guide for further experiments in searching for the LHT signals.·We firstly provided a precise prediction on the HZγ prodution at the (?)s=14TeV LHC at QCD NLO level. The effect of final photon emitted from the charged products of Higgs and Z-boson decays was estimated and a method to suppress this contamination in experiment was suggested.