Dark Matter Phenomenology At Particle And Astrophysical Platform

The discovery of Higgs boson with mass 125Ge V established the last piece of the Standard Model at the LHC(Large Hadron Collider),which is one of the most important achievements of the Standard Model of particle physics.Although the standard model is consistent with various experimental limits,it has some issues.Firstly,the model includes many mass parameters,mixings and origin of Higgs boson to be identified.Secondly,the theory does not include gravity.Finally,it is unable to provide suitable candidates for dark matter which has been indirectly confirmed by cosmological observations.This thesis focuses on dark matter.At present,a large number of cosmological experiments show that it indeed exists and accounts for about a quarter of the total matter in the universe.In order to explain the existence of dark matter,theoretical physicists have proposed new physical theories such as supersymmetric theory,composite Higgs theory,axion model,extra dimensional model and sterile neutrino model.Among them,the dark matter candidates given by supersymmetric theory and composite Higgs theory belong to WIMP(Weakly Interacting Massive Particles),but their properties are not exactly same.We firstly study the general WIMP(Weakly Interacting Massive Particles)dark matter candidates.In order to make our analysis as general as possible,we extend the standard model with the dark matter candidates obtained in terms of mixing between a new fermion singlet and two new doublets.In order to keep the dark matter particles stable,we apply Z₂ symmetry to them.Because the dark matter mainly participate in weak interaction,with the mass of order the weak scale.Therefore,it can be probed both at the dark matter direct detection experiments and the HL-LHC(High-Luminosity Large Hardon Collider).In the later case,we mainly analyze the background and signal of the electroweak processes through W and/or Z boson as the intermediate states,with two lepton or three lepton final states.The results show that dependent on the overall coupling constant,dark matter mass up to 170-210 Ge V can be excluded at 2?level and up to 175-205 Ge V can be discovered at 5?level at the14 Te V LHC with integrated luminosities 300 fb^-1 and 3000 fb^-1,respectively.Secondly,we study the minimum composite dark matter model SO(6)/SO(5),where five pseudo-Nambu Goldstone Bosons(p NGBs)are generated when the global symmetry SO(6)group is spontaneously broken to SO(5),with four of them identified as the Higgs doublet and the last one as dark matter.There are only three free parameters associated to the composite dark matter in this model.We study the dark matter phenomenology at various facilities.Our results reveal that a combination of dark matter direct detection experiments and the HL-LHC can distinguish these two kinds of dark matter models in certain dark matter mass range.Finally,we propose a decaying cold dark matter model to explain the excess of electron recoil events recently reported by XENON1T experiment.In this model,dark matter parent particle A decays to two daughter particles B,which makes B have velocity large enough to excite the electrons in the xenon atoms.The results show that,without violating limitations of dark matter detections and cosmological experiments,the model can explain the excess of recoil electron event.