B→ρB\to\rho, K∗K^* transition form factors in AdS/QCD model

We use the AdS/QCD distribution amplitudes for light mesons to calculate the transition form factors for B to $\rho$, $K^*$ decays. These form factors are then utilized to make predictions for the semileptonic $B\to\rho\ell\nu$ and dileptonic $B\to K^* \mu^+\mu^-$ decays. We compare our predictions to the experimental data from BaBar and LHCb.Comment: 7 pages, 3 figures. To appear in the proceedings of the 37th International Conference on High Energy Physics (ICHEP 2014) held in Valencia, Spain (2nd to 9th July 2014

Implications of the observation of dark matter self-interactions for singlet scalar dark matter

Evidence for dark matter self-interactions has recently been reported based on the observation of a spatial offset between the dark matter halo and the stars in a galaxy in the cluster Abell 3827. Interpreting the offset as due to dark matter self-interactions leads to a cross section measurement of sigma_DM/m ~ (1-1.5) cm^2/g, where m is the mass of the dark matter particle. We use this observation to constrain singlet scalar dark matter coupled to the Standard Model and to two-Higgs-doublet models. We show that the most natural scenario in this class of models is very light dark matter, below about 0.1 GeV, whose relic abundance is set by freeze-in, i.e., by slow production of dark matter in the early universe via extremely tiny interactions with the Higgs boson, never reaching thermal equilibrium. We also show that the dark matter abundance can be established through the usual thermal freeze-out mechanism in the singlet scalar extension of the Yukawa-aligned two-Higgs-doublet model, but that it requires rather severe fine tuning of the singlet scalar mass.Comment: 9 pages, 3 figures. V4: We included the Higgs width in equation and modified the paragraph following eqn 11 to reflect this change. This modification had no effect on our subsequent conclusions. The revised paper subsumes the erratum submitted to the journa

Phenomenology of Scalar Singlet Dark Matter in BSM Models

Approximately 85% of the mass of the universe is classified as dark matter, a type of matter outside the framework of the Standard Model. This thesis studies the phenomenology of three models that incorporate dark matter. Firstly, a singlet scalar dark matter candidate is added to two previously established models: the Higgslike dilaton and the Georgi-Machacek model. The parameters of these models are constrained using experimental results such as dark matter direct detection measurements, Higgs signal strengths, Higgs invisible width and the measured relic abundance of dark matter in the universe. The notion of self-interacting dark matter, derived from measurements of galaxy cluster Abell 3827, is also studied for SSDM extensions of both the Standard Model and the Two Higgs Doublet model. The parameters of these models are in each case tightly constrained by experiment