Kai Wang

Zhejiang University
Zhejiang Institute for Modern Physics, Department of Physics
20 Yugu Road,
Hangzhou, Zhejiang 310027, CHINA
Email: wangkai1 (at) zju.edu.cn

Education

• Ph.D. in Theoretical Physics, University of Wisconsin–Madison,   2008
• M.S. in Physics, Oklahoma State University,   2004
• B.S. in Physics, Zhejiang University,   2000

Teaching

• Particle Physics: Experimental Foundation of the Standard Model (coming soon)

Publications

• SLAC SPIRES      (arXiv.org)

Research Interest

• Collider Physics:
  LHC Physics of Standard Model, Beyond Standard Model Physics Searches at the LHC, Other Exotic Signatures at the LHC, Linear collider Physics
• Beyond Standard Model Physics Models:
  Supersymmetry Phenomenology, Neutrino Physics, Dynamical Electroweak Symmetry Breaking

arXiv hep-ph New
PDG Live
LEP Electroweak Working Group
Tevatron Electroweak Working Group
Tevatron New Pheno/Higgs Working Group

Select Talks

• A Revisit to Top AFB at Tevatron
  CDF collaboration has recently published various updated measurements on top quark forward-backward asymmetry in 1101.0034. The measured mass dependent asymmetry is significantly larger than the SM prediction from QCD NLO calculation as 3.5 sigma deviation. This is a comprehensive theory review on the Beyond Standard Model proposals to this anomaly, discussing their features, potential problems as well as their immediate predictions at the LHC.
  Video from Rutgers HEP
• Inverse See-saw in Supersymmetry
  To generate fermion mass from radiative corrections requires all the chiral symmetries associated with the fermion masses must be broken. So in order to make the radiative generated mass dominant, one can only tune the vacuum expectation to suppress the tree level mass. In this talk, I have presented two examples of fermion mass generation from radiative corrections in supersymmetric models where supersymmetry plays an important role to stabilize the suppressed tree-level masses without unbroken chiral symmetry. 1) To generate neutrino mass in a modified Wyler-Wolfenstein model from radiative corrections. 2) To generate charged lepton masses and down-type quark masses radiatively from Hu vev in MSSM.
• Explorations of the Top Quark Forward-Backward Asymmetry at the Tevatron
  Motivated by recent measurements of the top quark forward-backward asymmetry at the Tevatron, we study two new physics models that can contribute to a large asymmetry in ttbar production. To generate a large asymmetry while keeping the total production cross section unchanged, the new physics model must interfere with the leading QCD qqbar annihilation into ttbar pair. This requirement implies that the new physics can only be s-channel color octet with V-A coupling or t-channel physics. One example is to introduce a fermion number violating scalar with maximal flavor violation in t- channel. Due to spin correlation, Higgs-like scalar (color singlet or octet) mostly contribute to a negative asymmetry. The second model is a variation of chiral color model. To measure correlation between AFB and Mtt is particularly interesting and may provide much information about the couplings without the direct production.
• Probing B/L Violations in Extended Scalar Models at the LHC
  To test SM global symmetries U(1) Baryon Number or Lepton Number, there have been many attempts in the last decades, for instance, proton decay, neutron/anti-neutron oscillation or neutrinoless double beta decay. We propose two examples in the extended scalar models to test Baryon Number/Lepton Number violations effects at the coming LHC. The fermion number violation coupling enables scalar to couple to same-sign diquark/dilepton. The new color exotics as color sextet scalars can be produced in pair via QCD gauge interaction. It will decay into same-sign diquark. We will use the four top final state to search for color sextet scalar. It contributes to multijet plus same sign dilepton plus large missing transverse energy but the reconstruction is different from SUSY gluino/KK gluon as the same-sign dilepton comes from the resonance.
  Video from KITP, UCSB
• Testing Origin of Neutrino Mass at the LHC
  We propose a unique and clean signal to directly test a neutrino mass generation mechanism, namely the triplet model (type-II seesaw), at the CERN Large Hadron Collider. This is achieved by identifying the flavor structure of the lepton number violating decays of the charged Higgs bosons. The observation of singly charged Higgs will be particularly robust to distinguish the Normal Hierarchy (NH), the Inverted Hierarchy (IH) and the Quasi-Degenerate (QD) spectrum for the light neutrino masses since they are independent of the unknown Majorana phases, which could be probed via the doubly charged Higgs decays.
• Supersymmetry: A Phenomenology Introduction
  This three-day series of talks is designed to introduce basic collider phenomenology to graduate students at Zhejiang University. Given its rich phenomenology, we take Supersymmetry as an example.
• Gauge Mediated Split Supersymmetry
  SUSY contribution to Flavor violation/CP violation/Proton Decay all can be suppressed by increasing scalar masses. In Soft SUSY breaking lagrangian, gaugino masses/A-terms can only arise after R-symmetry breaking while scalar masses don’t. In Split SUSY case, one may expect a R-symmetry survive to low scale protect gaugino masses and at the same time, scalars are generated at high scale. However, one alternative realization is to introduce a new gauge symmetry, for instance, U(1) B-L and the messenger field couples to the new gaugino directly. Even though R-symmetry is broken, the Standard Model gauginos can only arise from multiple loops thus a naturally splitting between SM gauginos and scalars will arise.
• A Symmetry Approach to the MSSM mu-term
  The U(1) symmetry that forbids mu/B-terms in MSSM carries mixed QCD anomaly (SU(3) x SU(3) x U(1)) thus it can be categorized into Peccei-Quinn (PQ) symmetry. A pseudo-Goldstone boson axion is generated along the PQ symmetry breaking. However, the nuclear/cosmological/astrophysical bounds suggest the PQ symmetry breaking scale is coincidentally the intermediated scale in SUGRA mediated SUSY breaking. Thus the electroweak scale mu can be naturally generated by the PQ symmetry breaking and the same time, invisible QCD axion can provide a solution to strong CP problem.
• Hidden Symmetries and Their Implications
  When the global U(1) symmetries Baryon number and Lepton number are broken by ’t Hooft instanton within the Standard Model, there will be discrete remnants Z9/Z3 known as baryon parity/lepton parity. The discrete remnants are thus free of anomalies and can be embedded into gauged U(1)s and protected from quantum gravity violation. One of the most serious problem of low energy SUSY is that all Dim-6 operators ffff/cutoff squared can be reduced to Dim-5 operators with one SUSY scalar–gaugino loop as ffff/cutoff/MSUSY, for instance, the proton decay operator QQQL. Consequently, even though SUSY does break Baryon number symmetry, it can enhance the Baryon number violation effects. In this case, the gauged Baryon parity can be empolyed to avoid such fast proton decay.

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