The Phenomenological Research On Higgs And Dark Matter In The Next-to-minimal Supersymmetric Standard Model

The discovered 125 GeV Higgs boson in 2012 at the Large Hadron Collider(LHC)has verified the validity of the standard model(SM)at energy scales around TeV.But whether the observed Higgs particle is resonant still needs further experiments and demonstration.So far there is no clear signal for physics beyond the SM and the existence of dark matter(DM)cannot be explained reasonably in SM.Therefore,new physics models beyond the SM are required.As one of the most popular new physics models,the minimal supersymmetric standard model(MSSM)can provide an elegant solution to the hierarchy problem and predict the lightest neutralino as a DM candidate.Although MSSM has remarkable advantages,there are still some unsatisfactory problems,such as ?-problem and little hierarchy problem,which became exacerbated in recent years by the first run of LHC experiments.While these problems can be solved in the next-to-minimal supersymmetric standard model(NMSSM),which extends the Higgs sector of MSSM to include a gauge singlet field (?).When (?) develops a vacuum expectation value(VEV)vs,an effective ?-term(?eff=?vs)is dynamically generated and its magnitude is naturally at the electroweak scale.In the NMSSM,because of the interactions among Higgs fields ?(?)(?)_u·(?)_d,the squared mass of discoverd Higgs boson can receive a positive contribution at tree-level.Furthermore,the mass can be enhanced by the singlet-doublet Higgs mixing if the Higgs boson corresponds to the next-to-lightest CP-even Higgs state.So large radiative correction to the Higgs boson mass is unnecessary and the little hierarchy problem can be avoid.The parameter ml in NMSSM is the mass of Bino,and its value changes the composition of dark matter.And experiments such as XENON IT,LUX and PandaX have strict constraints on the cross section of dark matter.And the discovered 125 GeV Higgs boson can be naturally realized in the NMSSM.In this work we consider a scenario that the observed Higgs signal is the superposition of two mass-degenerate Higgs signals.