Preliminary Studies On The Relation Between Higgs Physics And Gravitational Wave From Phase Transition

Symmetry is an indispensable topic in modern physics.A study of symmetry at finite temperature is of great significance for understanding the dynamics of spontaneous symmetry breaking,especially for understanding the nature of phase transitions in the early Universe as phase transitions occur,the symmetry change.The standard cosmology model believes that the Universe starts from a very hot state.At the end of inflation,the Universe goes through the reheating / preheating process and cools to its current temperature as it expands.At present,it is generally believed that in the process of cosmic expansion,electroweak phase transition and QCD phase transition would occur one by one.The phase transition can be divided into first-order,second-order phase transition,or smooth cross-over according to the types.If the first-order phase transition occurs,it may leave traces--gravitational waves in space-time that can be observed.Lattice simulations indicate that the electroweak phase transition in the SM is a smooth cross-over.And many new physics models beyond the particle physics SM predict a first-order phase transition at the electroweak scale.At the same time,the first-order electroweak phase transition is an important part of the theory to explain the asymmetry between matter and antimatter in the Universe.And the gravitational wave during the SFOEWPT may be observed by the future space gravitational wave detection experiments(e.g.,LISA,Taiji,and Tianqin).In this way,the space-based gravitational wave detection experiments,and the collider experiments,can provide complementary constraints for new physics models of particle physics.To consider the effect of e EWSB's contribution on the electroweak phase transition,we study the feasibility of first-order electroweak phase transition in the Georgi-Machacek model in this paper.e EWSB helps establish a zero-temperature vacuum structure different from the SM,which can induce different modes of electroweak phase transitions in the early Universe,namely one-step and two-step SFOEWPT.However,both the Fermi constant and related collider experiments could yield significant constraints on e EWSB.The measurement of Higgs signal strength on the LHC imposes strict limits on the feasible parameter space of SFOEWPT.Meanwhile,to highlight the importance of triplet scalar VEV for SFOEWPT and related Higgs physical phenomenology,we introduce a new physical model(x SM)extended by real scalar particles and study the relationship between the SFOEWPT parameter space and the VEV of extra scalar.The two-step SFOEWPT can occur in the GM model when the mixing anglea between isospin doublet and isospin triplet states is around zero.The two-step SFOEWPT can be distinguished from the one-step SFOEWPT through the triple Higgs coupling searches and the low mass double-charged Higgs searches at colliders.The SFOEWPT feasible parameter space can be tested in the future 14 Te V LHC,the HL-LHC,the ILC,and CEPC.We have studied the possibility of future LHC detection in SFOEWPT parameter space,predicted the gravitational wave signal,and then found that the Higgs pair searches at lepton colliders can complement the GW searches of the SFOEWPT parameter spaces.Then we consider the phase transition in the new physics model with electroweak symmetry and an additional discrete symmetry.With the occurrence of electroweak phase transition,the spontaneous discrete symmetry breaking predicts the domain walls.If there is a small term in the potential that explicitly breaks the discrete symmetry,then the domain walls would decay before Big Bang Nucleosynthesis.In this thesis,by extending a complex scalar singlet field with Z3 symmetry,the gravitational waves generated by SFOEWPT and domain wall decay are discussed.The gravitational wave spectrum is of a typical two-peak shape.Future space-based interferometers can probe the high-frequency peak corresponding to the contribution of SFOEWPT.While the low-frequency peak is coming from the domain wall decay is far beyond the detection capability of the current Pulsar Timing Arrays and future Square Kilometer Array.