Our research interests are focused on Particle physics and Cosmology. We have made a series of influential and original work in various fields such as top quark physics, Higgs physics, early universe phase transition, baryon asymmetry, dark matter and quantum field theory methods. The main fields of research include:
In recent years, both of cosmological observations and ground exploration experiments have greatly promoted the development of extremely weak coupling phenomena such as dark matter detection and gravitational waves. The pulsar timing array (PTA) observations look for gravitational waves of nanohertz frequencies by measuring the arrival times of radio pulses from many highly stable millisecond-pulsars in the Milky Way. We performed a search for the stochastic gravitational-wave background (SGWB) from the first-order phase transition of the early universe using the Australia-based Parkes Pulsar Timing Array (PPTA) data set. The phase transitions with temperatures of∼1–100 MeV can be effectively constrained by the PPTA data, which are within predictions from low-scale dark phase-transition models and cosmological first-order QCD phase transitions. This work also has been published in PRL with Editor’s Suggestion.
In 2019, the first-ever image of the supermassive black hole (SMBH) M87* by the Event Horizon Telescope (EHT) leads us to a new era of black hole physics. We proposed a novel way of detecting axions around SMBHs by using the polarimetric measurements of the EHT. Such particles can accumulate around a rotating black hole through the superradiance mechanism, forming an axion cloud. Related work has been published on PRL. In 2021, We developed detailed data analysis methods to constrain the axion-photon coupling. Embedding the axion-induced birefringence into the radiative transfer framework for the first time, we simulated a movie of black hole images with oscillating linear polarization orientations at each point of the sky plane. We further gave prospects on how future observations, e.g., the upcoming EHT observations with higher time cadence or the Next Generation EHT (ngEHT), can probe a much larger parameter space with more detailed data. This work has been published in Nature Astronomy. All these efforts would increase more potential scientific exploration applications to the FAST radio telescope and the square kilometer array (SKA) in the coming future.
In 2020, the direct dark matter detection experiment XENON1T reported an excess in their low energy electron recoil data, appearing between 2–3 keV. Our studies showed that the excess of XENON1T can be naturally explained by boosted dark matter with a prediction of daily modulation, which was Editor’s Suggestion on PRL and featured in the journal of the American Physical Society (APS) to the public.
Higgs particle was first found through the Large Hadron Collider (LHC) in 2012, also known as God particle. In our classic paper “General Composite Higgs”, we proposed the most universal model framework of composite Higgs, which is cited 280 times till now. This work has illustrated the most crucial collider signal and was set as a reference model and cited many times by the LHC experimental group and experts from Review of Modern Physics. Meanwhile, he has discovered new symmetries such as maximum symmetry and trigonometric parity to solve the theoretical difficulties of the composite Higgs model. After the discovery of Higgs particles, we pointed out that the CP violation in the Higgs sector can explain the mystery of the origin of baryon asymmetry. We also proposed a new mechanism that satisfies the low-energy electric dipole moment experiment constraints, which provided an extremely key theoretical basis for the exploration of the phase transition in the early universe. All these four works have been published in PRL as the corresponding author.
Scattering is the most important and fundamental process in particle physics, which is formally a quantum transition between asymptotic states. It is natural to study the selection rules for transitions due to conservation laws, as practiced in theories of molecules, atoms, nuclei, as well as particle decays such as the Landau-Yang theorem. The selection rule in particle scattering due to angular momentum conservation is usually achieved by partial wave expansion, formulated for limited cases such as 2 to 2 scattering. It is therefore intriguing to apply the selection rule to generic scattering processes.
We derive the generalized partial wave expansion for N to M scattering amplitude in terms of spinor helicity variables. The basis amplitudes of the expansion with definite angular momentum j consist of the Poincaré Clebsch-Gordan coefficients. Moreover, we obtain a series of selection rules that restrict the anomalous dimension matrix of effective operators and how effective operators contribute to some 2 to N amplitudes at the loop level.