Precise Measurement Of The Standard Model And The Search For New Physics At The Future Large Hadron Electron Collider

The discovery of a Higgs boson at the CERN Large Hadron Collider(LHC)in 2012 means the last piece of the puzzle found in the Standard Model of particle physics.Since then,we have stepped into the so-called "After Higgs" era.In order to further satisfy the requirements of the research on the properties of the Higgs boson and the exploration of new physics beyond the Standard Model,a variety of projects about building new high-energy particle colliders have been put on the schedule.Among the many colliders,the future Large Hadron electron Collider(LHeC)is an economic choice,which intends to build a new electron accelerator near the LHC,using the existing 7 TeV proton beam at the LHC to collide with the accelerated electron beam,then generating abundant events for particle physics research.The greatly reduced QCD backgrounds the precise forward/backward detector help the LHeC with huge physical potential,in the meantime the property of the high energy scale is maintained as hadron colliders.First of all,LHeC as a deep non-elastic machine,it can precisely measure the parton distribution function(PDF)of nuclei and the electroweak parameters in the Standard Model;Secondly,a lot of Higgs bosons can be produced via the vector boson fusion process(VBF)at the LHeC,thus contributing to research on the properties of the Higgs boson as a "Higgs factory".Last but not least,the O(TeV)collision energy gives LHeC an ability to probe new physics beyond the Standard Model.With the LHC is upgraded to the Future Circular Collider(FCC),the LHeC also could be upgraded to FCC-eh accordingly,and further probe higher energy new physics.We can measure the charm quark Yukawa coupling yc at the LHeC,which is one of the keys to verifying the interaction between the Higgs boson and the second generation fermion.After analyzing the possible backgrounds in detail,we found the expected measuring precision of the charm quark Yukawa coupling at the LHeC is far better than results at the current hadron collider.The self-coupling of the Higgs bosons is closely related to the origin of the electroweak spontaneous breaking.we can well constrain the trilinear Higgs boson self-coupling λ3 via the one-loop correction of the VBF process at the LHeC.Due to the excellent precision of the LHeC’s detector,this indirect measurement constraint is better than the direct constraint from the double Higgs boson production in a certain range.In addition to the measurement of the Higgs boson associated parameters in the Standard Model,LHeC also can be used to study some rare production processes of the Higgs boson,such as the photo-production process.We calculated potential backgrounds of the photoproduction process in the large rapidity region in detail,estimated the significance of the signal using selection cuts and BDT methods,and found that it is still very challenging to observe the photo-production process at the LHeC.Finally,LHeC has a potential in probing supersymmetric particles,such as light Higgsinos.We studied the phenomenology of the light Higgsinos in the minimal supersymmetric standard model(MSSM).Due to the compressed spectrum,the signal lacks the observable decayed leptons in the final state.So it is hard to probe at hadron colliders.Based on the forward electron tagged at the ep collider,heavier Higgsinos could be approached at the LHeC or FCC-eh,which provided more stringent bounds on parameters in the supersymmetric model.