Guan-Nan Li

Some Predictions of Diquark Model for Hidden Charm Pentaquark Discovered at the LHCb

A bstractThe LHCb has discovered two new states with preferred JP quantum numbers 3/2− and 5/2+ from Λb decays. These new states can be interpreted as hidden charm pentaquarks. It has been argued that the main features of these pentaquarks can be described by diquark model. The diquark model predicts that the 3/2− and 5/2+ are in two separate octet multiplets of flavor SU(3) and there is also an additional decuplet pentaquark multiplet. Finding the states in these multiplets can provide crucial evidence for this model. The weak decays of b-baryon to a light meson and a pentaquark can have Cabibbo allowed and suppressed decay channels. We find that in the SU(3) limit, for U-spin related decay modes the ratio of the decay rates of Cabibbo suppressed to Cabibbo allowed decay channels is given by |Vcd|2/|Vcs|2. There are also other testable relations for b-baryon weak decays into a pentaquark and a light pseudoscalar. These relations can be used as tests for the diquark model for pentaquark.

Radiative Two Loop Inverse Seesaw and Dark Matter

A bstractSeesaw mechanism provides a natural explanation of light neutrino masses through suppression of heavy seesaw scale. In inverse seesaw models the seesaw scale can be much lower than that in the usual seesaw models. If terms inducing seesaw masses are further induced by loop corrections, the seesaw scale can be lowered to be in the range probed by experiments at the LHC without fine tuning. In this paper we construct models in which inverse seesaw neutrino masses are generated at two loop level. These models also naturally have dark matter candidates. Although the recent data from Xenon100 put stringent constraint on the models, they can be consistent with data on neutrino masses, mixing, dark matter relic density and direct detection. These models also have some interesting experimental signatures for collider and flavor physics.

Probing Higgs boson CP properties with tt̄H at the LHC and the 100 TeV pp collider

The Higgs boson H has the largest coupling to the top quark t among the standard model (SM) fermions. This is one of the ideal places to investigate new physics beyond SM. In this work, we study the potential of determining Higgs boson CP properties at the LHC and future 33 TeV and 100 TeV pp colliders by analyzing various operators formed from final states variables in ttH production. The discrimination power from SM coupling is obtained with Higgs boson reconstructed from H → γγ and H → bb. We find that ttbb process can provide more than 3σ discrimination power with 300fb−1 integrated luminosity in a wide range of allowed Higgs to top couplings for the LHC, the 33 TeV and 100 TeV colliders. For ttγγ the discrimination power will be below 3σ at the LHC, while for 33 TeV and 100 TeV colliders, more than 3σ sensitivity can be reached.

Comment on reparametrization invariance of quark–lepton complementarity

Abstract We study the complementarity between quark and lepton mixing angles (QLC), the sum of an angle in quark mixing and the corresponding angle in lepton mixing is π / 4 . Experimentally in the standard PDG parametrization, two such relations exist approximately. These QLC relations are accidental which only manifest themselves in the PDG parametrization. We propose reparametrization invariant expressions for the complementarity relations in terms of the magnitude of the elements in the quark and lepton mixing matrices. In the exact QLC limit, it is found that | V u s / V u d | + | V e 2 / V e 1 | + | V u s / V u d | | V e 2 / V e 1 | = 1 and | V c b / V t b | + | V μ 3 / V τ 3 | + | V c b / V t b | | V μ 3 / V τ 3 | = 1 . Expressions with deviations from exact complementarity are obtained. Implications of these relations are also discussed.

Lepton number violation and h → γγ in a radiative inverse seesaw dark matter model

A bstractWe study phenomenological implications of a radiative inverse seesaw dark matter model. In this model, because neutrino masses are generated at two loop level with inverse seesaw, the new physics mass scale can be as low as a few hundred GeV and the model also naturally contain dark matter candidate. The Yukawa couplings linking the SM leptons and new particles can be large. This can lead to large lepton flavor violating effects. We find that future experimental data on μ → eγ and μ − e conversion can further test the model. The new charged particles can affect significantly the h → γγ branching ratio in the SM. The model is able to explain the deviation between the SM prediction and the LHC data. We also study some LHC signatures of the new particles in the model.

The β angle as the CP violating phase in the CKM matrix

Abstract The CKM matrix describing quark mixing with three generations can be parameterized by three Euler mixing angles and one CP violating phase. In most of the parameterizations, the CP violating phase chosen is not a directly measurable quantity and is parameterization dependent. In this work, we propose to use the most accurately measured CP violating angle β in the unitarity triangle as the phase in the CKM matrix, and construct an explicit β parameterization. We also derive an approximate Wolfenstein-like expression for this parameterization.

THE α, β AND γ PARAMETRIZATIONS OF CP-VIOLATING CKM PHASE

The CKM matrix describing quark mixing with three generations can be parameterized by three mixing angles and one CP violating phase. In most of the parameterizations, the CP violating phase chosen is not a directly measurable quantity and is parametrization dependent. In this work, we propose to use experimentally measurable CP violating quantities,

Radiative inverse seesaw neutrino mass and dark matter

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