A dark matter solution from the supersymmetric axion model

We study the effect of the late decaying saxino (the scalar superpartner of the axion) and find out that there is a possible dark matter solution from a class of supersymmetric extensions of the invisible axion model. In this class of models, the saxino which decays into two axions acts as the late decaying particle which reconciles the cold dark matter model with high values of the Hubble constant. Recent observations of the Hubble constant are converging to $H_0=70\!-\!80\,{\rm km}\,{\rm sec}^{-1}\,{\rm Mpc}^{-1}$, which would be inconsistent with the standard mixed dark matter model. This class of models provides a plausible framework for the alternative cold dark matter plus late decaying particle model, with the interesting possibility that both cold dark matter and the extra radiation consist of axion.Comment: 11 pages, no figure, REVTEX 3.

The B ---> {\pi} K puzzle and the Bulk Randall-Sundurm model

The recent measurements of the direct CP asymmetries ($A_{CP}$) in the penguin-dominated $B\to K \pi$ decays show some discrepancy from the standard model (SM) prediction. While $A_{CP}$ of $B^+ \to \pi^0 K^+$ and that of $B^0 \to \pi^- K^+$ in the naive estimate of the SM are expected to have very similar values, their experimental data are of the opposite sign and different magnitudes. We study the effects of the custodial bulk Randall-Sundrum model on this $A_{CP}$. In this model, the misalignment of the five-dimensional (5D) Yukawa interactions to the 5D bulk gauge interactions in flavor space leads to tree-level flavor-changing neutral current by the Kaluza-Klein gauge bosons. In a large portion of the parameter space of this model, the observed nonzero $A_{CP}(B^+ \to \pi^0 K^+) - A_{CP}(B^0 \to \pi^- K^+)$ can be explained only with low Kaluza-Klein mass scale $M_{KK}$ around 1 TeV. Rather extreme parameters is required to explain it with M_{KK}\simeq 3\tev. The new contributions to well-measured branching ratios of $B \to K \pi$ decays are also shown to be suppressed.Comment: 18 pages, 2 figure

The CDF dijet excess and Z'_{cs} coupled to the second generation quarks

Recently the CDF collaboration has reported the excess in the dijet invariant-mass distribution of the Wjj events, corresponding to a significance of 3.2 standard deviations. Considering the lack of similar excesses in the $\gamma jj$ and $Z jj$ events yet, we propose a new Z' model: Z' couples only to the second generation quarks. Single production of \zsc as well as associated production with $W,\gamma, Z$ are mainly from the sea quarks. Only $W Z'$ production has additional contribution from one valence quark and one sea quark, which is allowed by CKM mixing. We found that if the new gauge coupling is large enough, marginally permitted by perturbativity, this new model can explain the observed CDF $Wjj$ anomaly as well as the lack of \gm jj and $Z jj$ anomalies. Vanishing coupling of Z'-b-b protects this model from the constraint of p pbar ->WH -> l\nu b \bar{b}.Comment: references adde

Hierarchical Mass Structure of Fermions in Warped Extra Dimension

The warped bulk standard model has been studied in the Randall-Sundrum background on $S^1/\Z\times\Z'$ interval with the bulk gauge symmetry $SU(3)\times SU(2)_L\times SU(2)_R\times U(1)_{B-L}$. With the assumption of no large cancellation between the fermion flavor mixing matrices, we present a simple analytic method to determine the bulk masses of standard model fermions in the almost universal bulk Yukawa coupling model. We also predict $U_{e3}$ element of MNS matrix to be near the experimental upper bound when the neutrino masses are of Dirac type.Comment: 16 page