Research Interests

My research interests:

The standard model of particle physics provides a well-established theory to describe the most basic building blocks of the universe called fundamental particles, governed by four fundamental forces. Over time and through many experiments, it has successfully explained almost all experimental results and precisely predicted a wide variety of phenomena. Despite its success, there are important questions that it does not answer:

  1. Origin of masses: why the Higgs boson mass is stabilized at the electroweak scale, and why the neutrino masses are so tiny? The Higgs self-interaction coupling (the last-missed parameter), is still not determined yet.

  2. Origin of matter: the standard model cannot explain the observed 5% ordinary matter (the matter antimatter asymmetry). It also fails to explain the dark matter and dark energy, around 95% of the matter density in the standard model of cosmology.

  3. Scale of new physics: although many null experimental results, we are always curious to know the scale of new physics. Effective field theory provides a framework to study new physics without new particles even new physics scale is unknown.

To understand our universe and investigate these questions, we rely on two solid theoretical frameworks: quantum field theory, and general relativity. On the other hand, we know physics is essentially an experimental science: a beautify theory, with predictions, needs to be supported by various experimental evidences. My current research interests focus on the effective field theories framework and application at the particle, hadronic, and nuclear levels, to answer questions of the Higgs and neutrino masses and potential, the matter-antimatter asymmetry, and dark matter nature.

1. The energy frontier: Higgs Boson to explain origin of mass and matter

The discovery of the Higgs boson at the large hadron collider (LHC) is a milestone in the history of particle physics. The properties of the Higgs boson, such as the mass, width, and couplings, have been measured very precisely and agree with the predictions from the standard model within experimental error-bar. However, the Higgs self-interaction coupling is still not observed within 5 sigma confidence level at the LHC run II, and thus the shape of the Higgs potential still cannot be determined. The Higgs boson physics still has the following puzzles: (1) why the Higgs boson vacuum expectation value is stabilized at the electroweak scale, instead of the Planck scale? (2) Can the shape of the Higgs potential be different from the prediction from the standard model? (3) Whether a microscopic mechanism similar to superconductor exists in the Higgs mechanism? (4) Is the electroweak phase transition in the early universe the second order (cross-over) or the first order? (5) Can the Higgs boson provide successful baryogenesis mechanism, electroweak baryogenesis and how to test this mechanism? To answer these questions, we rely on the experimental data from colliders, such as large hadron collider, and future lepton colliders. The shape of the Higgs potential, and the phase transition pattern can be verified at the future Higgs factory.

2. The intensity frontier: neutrino to explain origin of mass and matter

The neutrino oscillation, observed by the SuperK and SNO, shows that neutrinos are massive particle, which provides the first firm evidence of beyond the standard model. Currently neutrino physics has vast experimental progress because of many on-going/planned neutrino experiments: NoVA/Dune, T2K/T2HK, etc. However, these experimental results can still not address theoretical puzzles from the tiny neutrino masses: (1) why neutrino masses are far smaller than the proton mass and the electron mass? (2) Are neutrinos Dirac or Majorana-type fermion? (3) Whether the lepton number is violated? (4) Whether there are large CP violation in the neutrino sector? (5) Can the neutrino provide successful baryogenesis mechanism, the leptogenesis, and how to test this mechanism? These question can be answered by the low-energy but high-luminosity experiments, such as neutrino-less double beta decay, neutrino long and short baseline, nuclear electric dipole moment, neutron-antineutron oscillation, etc. These experiments have relatively lower cost and would be one of the important directions in future.

3. The cosmic frontier: dark matter to explain the early universe

The existence of a vast amount of dark matter in the Universe is supported by many astrophysical and cosmological observations. The latest CMB measurements indicate that it constitutes approximately a 27% of the Universe energy density. Given that the standard model of particle physics does not contain any viable candidate to account for it, dark matter, if it is a fundamental particle, can be regarded as one of the clearest hints of new physics. Currently all the evidences of dark matter comes from its gravitational interaction, and we do not know any info on its particle nature. Thus there are lots of questions related to its particle nature: (1) Is the dark matter fundamental particle? (2) If so, what is its properties, such as spin, mass and couplings? (3) Whether dark matter ever has thermal equilibrium with the standard model particles? (4) Whether the dark matter is cold or warm after it freeze-out or freeze-in? (5) How dark matter affects the growth of the cosmological perturbation and the structure formation? To address dark matter’s particle nature, the underground direct detection experiments are running to exclude more and more parameter regions for the wimp particle. On the other hand, the light dark matter, which is easy to escape from the direct detection, provide richer cosmological signatures in the cosmic microwave background and Lyman alpha forests, and so on.

4. Effective Field Theories: interplay among particle, hadronic and nuclear physics

Problems with separated scales often appear in nature, and we intuitively know that it is most convenient to only work with degrees of freedom that are relevant for a particular scale. You never worry about physics of the atoms when designing bridges, nor try to track each and every molecule of a gas through phase space. As modern view of quantum field theory, effective field theory (EFT) is a successful paradigm to understand particle physics at different scales: most of the details of small distance physics are irrelevant for the description of longer-distance phenomena. EFT is a tool which has been applied to, but not limited to, new physics beyond the standard model (SMEFT), chiral symmetry breaking (chiral EFT) and heavy particle EFT at the hadronic and nuclear scale, and effective description of quantum gravity (gravity EFT), etc. The null experimental data at the LHC motivate us adapt the SMEFT-LEFT-ChiralPT-nuclearEFT pipeline to describe new physics effects at various scales: the Higgs - top quark - W/Z boson physics at the electroweak scale, the bottom - charm - kaon physics at the hadronic scale, and the nucleon - pion - nuclear physics at the nuclear scale. The low energy probe of high energy physics gives us an interplay among several different scales and is thus quite suitable to be implemented in the EFT framework.



  1. 质量起源问题:标准模型还存在最后一个未测量的参数,就是希格斯自相互作用;希格斯粒子和中微子的质量起源仍然存在疑难;

  2. 物质起源问题:粒子物理标准模型不能解释物质反物质不对称性,也不能解释暗物质的来源。


1. 希格斯和中微子的质量起源:希格斯本质和势能,电弱相变和引力波,超对称/复合/额外维

大型强子对撞机(LHC)上希格斯粒子的发现是粒子物理的一个里程碑式的进展。目前,希格斯粒子的质量和性质,已经被测量到很高的精度且和标准模型的预言基本一致。但是,LHC还没有确定希格斯粒子的自相互作用,因此也就不能确定希格斯的势能形式。希格斯物理仍然面临如下疑难:为什么势能最小值稳定在电弱能标? 希格斯的势能形式是否可以和标准模型预言的形状不同? 希格斯势能是否存在类似于超导理论的微观机制? 早期宇宙中的电弱破缺引起的电弱相变是一阶还是二阶相变?


2. 有效场论理论框架:标准模型有效场论,手征有效场论,非平衡量子场论及宇宙学应用



3. 宇宙正物质和暗物质的起源:重子轻子生成,非热暗物质/惰性中微子/轴子,及其宇宙学


另一方面,我们的可观测宇宙是正物质主导的,那么反物质到哪里去了? 萨克哈罗夫提出了重子生成机制,为了实现正反物质不对称性需要三个条件:重子数破坏,C和CP破缺,和偏离热平衡。粒子物理标准模型无法提供较大的CP破缺强度,且并不存在明显的偏离热平衡过程,因此为了解释正反物质不对称性,需要对标准模型进行扩展,希格斯粒子和中微子是解决重子生成问题的主流机制。

4. 能量和亮度前沿:对撞机信号,暗物质直接探测/中微子相干散射,无中微子双贝塔衰变