Measurements Of The CP Property Of The Top-Higgs Yukawa Coupling And Its Phenomenological Study

Since the discovery of the Higgs boson at the Large Hadron Collider(LHC)in 2012,measuring the properties of the Higgs boson and its couplings to other particles have become one of the main targets of the collider physics.To determine whether the Higgs boson has CP violated effects is one of the driving forces behind precision measurements at the LHC.This is because in some models beyond the Standard Model(BSM),the interaction between the Higgs boson and fermions has CP violated effects.Additionally,baryon number asymmetry in cosmology demands CP violation in fundamental interactions.This thesis focuses on the measurements of the CP property of the interaction between the Higgs boson and top quark at the CMS experiment and its phenomenological study.The ttH production contains the vertex of the Higgs boson and top quark and is the most important process to study the top Yukawa interaction.Among all the final states,H→γγ is one of the most sensitive channel to measure the ttH production.Therefore,I measured the CP property of the top Yukawa coupling in the ttH production in the H→γγ final state.The data used in the measurement is collected by the CMS detector at the LHC,based on proton-proton collisions at a center-of-mass energy(?)=13 TeV,corresponding to an integrated luminosity of 137 fb-1.The CP structure of the top Yukawa coupling is measured,resulting in an exclusion of the pure CP-odd structure of the top Yukawa coupling at 3.2σ.The fractional contribution of the CP-odd component is measured to be fCP=0.0 ± 0.33.The H→4l channel,which can be full reconstructed and has high mass resolution,is also an important channel to sutdy the properties of the Higgs boson.The kinematic effects of the Higgs boson decaying to four-lepton final state and its production in association with two jets or top quarks are analyzed.A simultaneous measurement is perfomed for the Higgs boson couplings to two gluons(Hgg)and two top quarks(Htt).The CP measurement of the Htt interaction is combined with the measurement in the H→γγ final state.The gluon fusion process,dominated by the top quark loop,is also sensitive to the CP property of the Higgs boson.This thesis presents the first measurement of the the CP property of the Htt and effective Hgg couplings in the ttH and ggH productions simultaneously.In addition to the measurements of top Yukawa coupling in the ttH and ggH,this thesis includes the phenomenology work proposing using tt production with electroweak loop corrections as an alternative approach to measure the CP property of the Higgs boson.With the calculation of the one loop electroweak corrections including arbitrary CP mixtures in the Standard Model Effectice Field Theory,I extract the CP property of the Higgs boson from the kinematics of the tt final particles.This approach relies on the large cross section of tt production and the excellent control of high order corrections.The work finds that loop sensitivity in the tt production and onshell sensitivity in the ttH and tqH provide complementary handles over a wide range of parameter space.Feasibility study of measuring the CP property of the top Yukawa interaction in the tWH production is also presented.Although the cross seciton of the tWH production is small,it can impose certain constraints on the CP structure.The search for the light Higgsino in the Minimal Supersymmertric Standard Model(MSSM)is an important test of the criteria of the naturalness in the supersymmtery.However,direct searches for the light Higgsino are well-known as a changeling problem at the LHC.This thesis proposes search for the light Higgsino through the VBF process in the future electron-proton colliders.The work finds that the Higgsino with mass 95/145 GeV can be reached at 2σ level at future LHeC/FCCeh with a luminosity 3000 fb-1.