Probing Dark Matter Particles On CEPC

From the end of the 19th Century and the beginning of the 20th century,observa-tions on the velocity starts orbiting the centre of the galaxy showed significant devia-tion from the prediction based on Newtonian gravity theory.Many theories and models were proposed to solve this issue,including modified Newtonian dynamics(MOND),invisible stars and dark matter.In this thesis we briefly recap the history of the dark matter and offer a detailed description on the dark matter models we studied on the CEPC.The circular electron positron collider(CEPC)is the next generation e?e-collider scheme proposed by Chinese high energy physics community.lt is projected to run on 3 different energy scales,(?)S = 240,158-172 and 91.2 GeV.It will generate a very large amount of Higgs events,enabling a measurement on its property to an unprecedented precision and making further studies on fundamental physical problems like the electroweak spontaneous symmetry breaking or the origin of mass possible through Higgs.We investigate the collider signatures for a variety of dark matter models at the proposed circular electron positron collider(CEPC).We analyze the monophoton sig-nals arising from dark matter models as well as from the standard model.The energy and angular distributions of the signal process and the standard model background are compared;a set of detector cuts are proposed to maximize the signal to background significance.We find that the future CEPC collider has sensitivity to the parameter space for a number of dark matter models.Specifically,the parameter space of 5 GeV millicharged dark matter can be probed down to??-0.1 with an integrated luminosity of 5.6 ab-1,which is unexplored so far.The structure of this thesis can be stated as follows:the first section is an overview on the history of human studies on dark matter,the second would be an introduction to the CEPC collider,the third section then covers the models we study using the CEPC,the fourth is a detailed description on our methodology,the fifth will be a summary of our results and the last section is the conclusion and the outlook.