Ci Zhuang

Gauge-singlet dark matter in a left-right symmetric model with spontaneous CP violation

We propose a dark matter (DM) scenario in an extension of a left-right symmetric model with a gauge-singlet scalar field. The gauge-singlet scalar can automatically become a DM candidate, provided that both P and CP symmetries are only broken spontaneously. Thus no extra discrete symmetries are needed to make the DM candidate stable. After constraining the model parameters from the observed relic DM density we make predictions for direct detection experiments. We show that for some parameter range, the predicted weakly interacting massive particle-nucleon elastic scattering cross section can reach the current experimental upper bound, which can be tested by the experiments in the near future.

Dark matter constraints on the left-right symmetric model with Z(2) symmetry

In the framework of the left-right symmetric model, we investigate an interesting scenario, in which the so-called vacuum expectation value (VEV)-seesaw problem can be naturally solved with Z(2) symmetry. In such a scenario, we find a pair of stable weakly interacting massive particles (WIMPs), which may be the cold dark matter candidates. However, the WIMP-nucleon cross section is 3-5 orders of magnitude above the present upper bounds from the direct dark matter detection experiments for m similar to 10(2)-10(4) GeV. As a result, the relic number density of two stable particles has to be strongly suppressed to a very small level. Nevertheless, our analysis shows that this scenario cannot provide very large annihilation cross sections so as to give the desired relic abundance except for the resonance case. Only for the case if the rotation curves of disk galaxies are explained by the modified Newtonian dynamics (MOND), the stable WIMPs could be as the candidates of cold dark matter.

Constraining Charming Penguins in Charmless B Decays

We discuss the correlations of charming penguin contributions to

Exclusive B ---> PV Decays and CP Violation in the General two-Higgs-doublet Model

B\to\pi\pi

Constraining charming penguins in charmless B → ππ, πK and KK decays

,

Exclusive B → P V decays and C P violation in the general two-Higgs-doublet model

\pi K

ExclusiveB→PVdecays andCPviolation in the general two-Higgs-doublet model

and KK using approximate flavor SU(3) symmetry. Strong constraints are found from the direct CP asymmetries especially in

Implications of new data in charmless B decays

\pi K

Charmless B-s -> PP, PV, VV decays based on the six-quark effective Hamiltonian with strong phase effects II

modes. We make a global fit to the latest data and find that only a small charming penguin is allowed, and the size of color-suppressed tree amplitude (C) relative to tree amplitudes (T) remains large

Signal of New Physics and Test of Isospin-SU(3) Relations and CP Violation in Charmless B Decays

C/T\simeq0.6