Axion Dark Matter Related Research

Astronomy observations on the behavior of gravitational effects of galaxies and galaxy clusters have given the earliest evidence of the existence of dark matter.Subsequently,more and more cosmological and astronomical observational evidences have confirmed the existence of dark matter.We believe that there may be very weak interactions between dark matter and Standard Model particles.At present,the matter composition of the universe is composed of 4.9%ordinary baryonic matter,26.8%dark matter and 68.3%dark energy.A large number of theoretical models of dark matter particles have been proposed under the framework of particle physics.Although the existence of dark matter has not been directly observed,the theoretical framework of dark matter is constantly being revised based on current experimental results.This article first reviews the relevant experimental evidence for the existence of dark matter and the standard model of particle physics.Through research on the rotation curve of galaxies,the big bang nucleosynthesis,the cosmic microwave background radiation,the formation of large-scale galaxies,etc.,it is found that quarks,leptons,gauge bosons,and Higgs particles in the Standard Model are far from providing the basics of the universe.Component,due to the establishment of the ACDM model,the standard model of cosmology,we have reason to believe that dark matter and dark energy are an indispensable part of the material energy in the universe.Then we discussed the dark matter model of heat generation.In the process of gradual cooling as the universe expands,one or some heavy particles that originally existed in the thermal bath of elementary particles and are in thermal equilibrium with other particles will be removed from the thermal bath of the universe when the temperature drops below the decoupling temperature.Frozen,if its life span is long enough,it can be used as a dark matter candidate today.The abundance of dark matter given by this heat generation mechanism is related to its mass and cross-section to annihilation.The calculation found that if its mass is near the TeV energy scale and the annihilation cross section is on the order of pb(weak interaction magnitude),then its residual abundance can just explain today’s dark matter observations.This is called the WIMP(Weakly Interacting Massive Particle)miracle.We use numerical simulation results to discuss the influence of scattering cross section and dark matter mass on the abundance of dark matter today.Finally,in Chapter 3,we discussed the theoretical origin of axion dark matter and several common axion models,as well as the remaining abundance of cold axon dark matter models generated by the misalignment mechanism.Since the massive particles predicted by WIMP dark matter have not been seen in various direct detection experiments,and the current direct detection experiments have been close to the neutrino background,there are reasons to look for light dark matter models other than WIMP.Axion is an excellent candidate for this light dark matter particle.Axion has a strong theoretical motivation,and it is the most natural solution to the strong CP problem.At the same time,the misalignment mechanism can generate enough cold axons to explain the dark matter in the universe.We numerically simulated the relationship between the abundance of cold axons produced by the misalignment mechanism,the initial phase of the axons,and the PQ breaking energy scale.Finally,we give a summary and outlook of the full text.