New Physics Phenomenology Of Higgs Based On Effective Lagrangian

Search for new physics is the most important goal in particle physics after the discovery of the Higgs boson. Until now, none of the known new physics models has any evidence in experiments. So compared to testing new physics model by model, it is more efficient to do it in a model independent way. Most new physics models, if their high energy degrees of freedom are integrated out, can be expressed by the effective Lagrangian containing high-dimension effective operators with different Wilson coefficients. As a consequence, the phenomenology based on effective Lagrangian offers a benchmark for model testing and is widely used in research on new physics. This paper focuses on the effective Lagrangian containing Higgs bosons. We formulate the effective interactions of Higgs bosons in the framework of dimension-6 operators, and study their phenomenology at the LHC and Higgs factories.In the part related to LHC, we consider a multi-Higgs system with two lightest Higgs bosons that are neutral. The lighter one h is the discovered Higgs boson, while the heavier one H is assumed to have dimension-6 anomalous couplings. The obtained anomalous couplings contain extra parameters reflecting the Higgs mixing effect. We calculate the constraints on the anormalous coupling constants of H from the requirement of the unitarity of the VV-scattering S matrix, and propose the idea that H can avoid being excluded by the LHC data if its production and decay rates are reduced. From the unitarity and exclusion bounds we obtain the range of the anomalous coupling constants,with which H is not excluded by the yet known theoretical and experimental constraints,and could be detected at the 14 TeV LHC through VH?associated production.In the Higgs factories part, this paper propose that the e+e-â†' γh process can be useful to detect new physics effects on h. We calculate the cross section in both the Standard Model and effective Lagrangian approach, and find that γh is more sensitive to some dimension-6 operators than the current experimental data. Further more, in the language of effective Lagrangian, the new physics effects on γh have only two degrees of freedom, much fewer than the Higgsstrahlung process. This point could be used to reduce the degeneracies of Wilson coefficients and get the exact ranges of the coefficients.Those are very important for an overall understanding of new physics models: only those models consistent with the coefficient ranges could survive. In the optimistic scenario new physics effects may be observed at the CEPC or TLEP in the early stage of their run,or else a more severe constraint on the Wilson coefficients will be obtained.