Electroweak Phase Transition in Georgi-Machacek Model: Gravitational Wave and Collider
The discovery of Higgs and the observation of Gravitational Wave are two of the biggest events in our community in this decade. The Higgs is the last piece in the Standard Model. However, the SM is not the final. There are still puzzles that are not addressed in SM. One of them is the baryon asymmetry of the Universe. Electroweak Baryogenesis is one of the framework that can explain this asymmetry. However, in this framework, the electroweak phase transition should be 1st order in order to provide out-of-thermal-equilibrium environment. This requires the extension of SM since with the observed 125 GeV Higgs, we can only have 2nd order phase transition in SM. Further, the 1st order phase transition can produce gravitational wave through bubble nucleation. After the redshift from the time it produced to now, the frequency is around mHZ, which is just in the range of future gravitational wave detectors. Hence, the gravitational wave detection is already has the sensitivity to probe physics beyond SM. After a brief introduction about the electroweak phase transition and the its induced GW, I will use the Georgi-Machacek model as an example model to illustrate the complementary between GW detections and Collider searches.