Probing New Physics With Higgs Bosons

The discovery of the Higgs boson h(125GeV)is a turning point of particle physics.It is the only fundamental scalar particle predicted by the Standard Model(SM)which completes the particle spectrum of SM,but it leaves a number of fundamental problems unsolved.The SM is only an effective theory below a certain high energy scale.Many of the difficult problems of SM are related to the properties of the Higgs boson,so it is important to precisely probe the properties of the Higgs particle and determine whether it deviates from the prediction of SM.The discovered Higgs boson h(125GeV)may be just the tip of a huge iceberg,and there may be new physics beneath the water.Searching for new Higgs particles beyond h(125GeV)is an important goal for LHC Run-2 and the upcoming High Luminosity Upgrade of LHC(HL-LHC).The Two Higgs Doublets Model(2HDM)is a minimal and simplest extension to the Higgs sector of SM.It contains five physical Higgs particles:two neutral scalar particles h~0,H~0,a neutral pseudoscalar particle A~0,and a pair of charged scalar particles H~±.This thesis will study H~0production,and H~±and A~0production respectively.For H~0,we study the process pp?H~0?h~0h~0?WW~*WW~*over the H~0mass range 300-800GeV,and analyze the detectable region in the 2HDM parameter space.The charged Higgs bosons is a unique signature beyond SM and a key prediction of 2HDM.This thesis will study the process pp?H~+?A~0W~+,and analyze the detectable range of H~±mass200-600GeV and A~0mass 40-400GeV.Our analysis and predictions of the neutral and charged Higgs searches were adopted by ATLAS collaboration.The international particle physics community is actively planning to build the e~+e~-collider with collision energy 250GeV as a Higgs factory.It will produce and accurately measure the Higgs bosons.In this thesis,we study the probe of new physics scales at the Higgs factory via model-independent effective theory approach.Before discovering any new particle,all new physics effects can be described by a set of higher dimensional effective operators.By combining the Higgs boson measurements and the electroweak precision tests at the Higgs factory,we derive the lower limit on the new physics scale for each high dimensional operator.We derive that the Higgs factory can indirectly probe the new physics scale up to the range of 10-30TeV,which fully covers the direct search range of the next generation high energy pp collider.This study provides a key physics justification for the conceptual design of CEPC(PreCDR and CDR).