In this work we study the two-body hadronic charmed meson decays, including both the PP and VP modes. The latest experimental data are first analyzed in the diagrammatic approach. The magnitudes and strong phases of the flavor amplitudes are extracted from the Cabibbo-favored decay modes using $\chi${}2 minimization. The best-fitted values are then used to predict the branching fractions of the singly Cabibbo-suppressed and doubly Cabibbo-suppressed decay modes in the flavor SU(3) symmetry limit. We observe significant SU(3) breaking effects in some of the singly Cabibbo-suppressed channels. In the case of VP modes, we point out that the AP and AV amplitudes cannot be completely determined based on currently available data. We conjecture that the quoted experimental results for both Ds+$\rightarrow${}K\ifmmode\bar\else\textasciimacron\fi{}0K*+ and Ds+$\rightarrow${}$\rho${}+$\eta${}$'${} are overestimated. We compare the sizes of color-allowed and color-suppressed tree amplitudes extracted from the diagrammatical approach with the effective parameters a1 and a2 defined in the factorization approach. The ratio |a2/a1| is more or less universal among the D$\rightarrow${}K\ifmmode\bar\else\textasciimacron\fi{}$\pi${}, K\ifmmode\bar\else\textasciimacron\fi{}*$\pi${}, and K\ifmmode\bar\else\textasciimacron\fi{}$\rho${} modes. This feature allows us to discriminate between different solutions of topological amplitudes. For the long-standing puzzle about the ratio $\Gamma${}(D0$\rightarrow${}K+K-)/$\Gamma${}(D0$\rightarrow${}$\pi${}+$\pi${}-), we argue that, in addition to the SU(3) breaking effect in the spectator amplitudes, the long-distance resonant contribution through the nearby resonance f0(1710) can naturally explain why D0 decays more copiously to K+K- than $\pi${}+$\pi${}- through the W-exchange topology. This has to do with the dominance of the scalar glueball content of f0(1710) and the chiral-suppression effect in the decay of a scalar glueball into two pseudoscalar mesons. The same final-state interaction also explains the occurrence of D0$\rightarrow${}K0K\ifmmode\bar\else\textasciimacron\fi{}0 and its vanishing amplitude when SU(3) flavor symmetry is exact. Owing to the G-parity selection rule, Ds+$\rightarrow${}$\pi${}+$\omega${} does not receive contributions from the short-distance W-annihilation and resonant final-state interactions, but it can proceed through the weak decays Ds+$\rightarrow${}$\rho${}+$\eta${}($'${}) followed by the final-state rescattering of $\rho${}+$\eta${}($'${}) into $\pi${}+$\omega${} through quark exchange.

We analyze the theoretical and phenomenological considerations for the electroweak phase transition and dark matter in an extension of the standard model with a complex scalar singlet (cxSM). In contrast with earlier studies, we use a renormalization group improved scalar potential and treat its thermal history in a gauge-invariant manner. We find that the parameter space consistent with a strong first-order electroweak phase transition (SFOEWPT) and present dark matter phenomenological constraints is significantly restricted compared to results of a conventional, gauge-noninvariant analysis. In the simplest variant of the cxSM, recent LUX data and a SFOEWPT require a dark matter mass close to half the mass of the standard model-like Higgs boson. We also comment on various caveats regarding the perturbative treatment of the phase transition dynamics.

The decays of B mesons to a pair of charmless pseudoscalar (P) mesons are analyzed within a framework of flavor SU(3). Symmetry breaking is taken into account in tree (T) amplitudes through ratios of decay constants; exact SU(3) is assumed elsewhere. Acceptable fits to $\overrightarrow{B}\pi \pi$ and $\overrightarrow{B}K\pi$ branching ratios and CP asymmetries are obtained with tree, color-suppressed $\mathrm{}\left(C\right),$ penguin $\mathrm{}\left(P\right),$ and electroweak penguin ${(P}_{\mathrm{EW}})$ amplitudes. Crucial additional terms for describing processes involving $\eta$ and ${\eta }^{\prime }$ include a large flavor-singlet penguin amplitude (S) as proposed earlier and a penguin amplitude $P_{\mathrm{tu}}$ associated with intermediate t and u quarks. For the $B^{+}\to {\pi }^{+}{\eta }^{\prime }$ mode a term $S_{\mathrm{tu}}$ associated with intermediate t and u quarks also may be needed. Values of the weak phase $\gamma$ are obtained consistent with an earlier analysis of $\overrightarrow{B}\mathrm{VP}$ decays, where V denotes a vector meson, and with other analyses of CKM parameters.

We study the implications of flavor-changing neutral currents (FCNC’s) in a model with the $SU(2{)}_l\times SU(2{)}_h\times U(1{)}_Y$ electroweak gauge symmetry for several anomalies appearing in $b\to s\ell \overline{\ell }$ induced $B$ decays in LHCb data. In this model, $SU(2{)}_l$ and $SU(2{)}_h$ govern the left-handed fermions in the first two generations and the third generation, respectively. The physical $Z$ and $Z^{\prime }$ generate the $b\to s$ transition at tree level, leading to additional contributions to the $b\to s$ semileptonic operators ${\mathcal{O}}_{9,10}$. We find that although $B_s\text{−}{\overline{B}}_s$ mixing constrains the parameters severely, the model can produce values of ${\mathcal{C}}_{9,10}^{\mathrm{NP}}$ in the range determined by Descotes-Genon et al. (Global analysis of $b\to s\ell \ell$ anomalies, arXiv:1510.04239) for this scenario to improve the global fit of observables in decays induced by the $b\to s\mu \overline{\mu }$ transition. The $Z^{\prime }$ boson in this model also generates tree-level FCNC’s for the leptonic interactions that can accommodate the experimental central value of $R_K=\mathcal{B}(B\to K\mu \overline{\mu })/\mathcal{B}(B\to Ke\overline{e})=0.75$. In this case, the model predicts sizable branching ratios for $B\to Ke\overline{\tau }$, $B\to K\tau \overline{e}$, and an enhancement of $B\to K\tau \overline{\tau }$ with respect to its standard model value.