We study $B\to J/\Psi {\eta }^{(\prime )}$ decays and suggest two methods to determine the $\eta -{\eta }^{\prime }$ mixing angle. We calculate not only the factorizable contribution in the QCD factorization scheme but also the nonfactorizable hard spectator corrections in the pQCD approach. We get the branching ratio of $B\to J/\Psi \eta$, which is consistent with recent experimental data, and predict the branching ratio of $B\to J/\Psi {\eta }^{\prime }$ to be $7.59\times {10}^{-6}$. Two methods for determining the $\eta -{\eta }^{\prime }$ mixing angle are suggested in this paper. For the first method, we get the $\eta -{\eta }^{\prime }$ mixing angle to be about $-13.1°$, which is consistent with others in the literature. The second method depends on fewer parameters and can thus be used to determine the $\eta -{\eta }^{\prime }$ mixing angle with better accuracy but needs, as an input, the branching ratio for $B\to J/\Psi {\eta }^{\prime }$, which should be measured in the near future.

We compute the $\mathcal{O}({\alpha }_s^2)$ corrections to the differential rate of the semileptonic decay $b\to c\ell {\nu }_{\ell }$ at the “intermediate recoil” point, where the $c$-quark mass and the invariant mass of the leptons are equal. The calculation is based on an expansion around two opposite limits of the quark masses $m_{b,c}$: $m_c\simeq m_b$ and $m_c\ll m_b$. The former case was previously studied; we correct and extend that result. The latter case is new. The smooth matching of both expansions provides a check of both. We clarify the discrepancy between the recent determinations of the full NNLO QCD correction to the semileptonic $b\to c$ rate, and its earlier estimate.

Padé approximants can be used to go beyond vector meson dominance in a systematic approximation. We illustrate this fact with the case of the pion vector form factor in the spacelike region and extract values for the first two coefficients of its Taylor expansion around $Q^2=0$. Padé approximants are shown to be a useful and simple tool for incorporating information from higher energies, allowing in some cases an improved determination of these Taylor coefficients relative to other methods.

The HESS array of Cherenkov telescopes has performed, from 2004 to 2007, a survey of the inner galactic plane at photon energies above 100 GeV. About 400 hours of data have been accumulated in the region between $-30$ and $+60\mathrm{degrees}$ in galactic longitude, and between $-3$ and $+3\mathrm{degrees}$ in galactic latitude. Assuming that dark matter is composed of weakly interacting massive particles, we calculate here the HESS sensitivity map for dark matter annihilations, and derive the first experimental constraints on the (”minispikes”) scenario, in which a gamma-ray signal arises from dark matter annihilation around intermediate mass black holes. The data exclude the proposed scenario at a 90% confidence level for dark matter particles with velocity-weighted annihilation cross section $\sigma v$ above ${10}^{-28}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ and mass between 800 GeV and 10 TeV.

We present a search for the decays $B\to K^{*}\nu \overline{\nu }$ using $454\times {10}^{6}B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the BABAR detector at the SLAC PEP-II $B$-Factory. We first select an event sample where one $B$ is reconstructed in a semileptonic or hadronic mode with one charmed meson. The remaining particles in the event are then examined to search for a $B\to K^{*}\nu \overline{\nu }$ decay. The charged $K^{*}$ is reconstructed as $K^{*+}\to K_S^0{\pi }^{+}$ or $K^{*+}\to K^{+}{\pi }^0$; the neutral $K^{*}$ is identified in $K^{*0}\to K^{+}{\pi }^{-}$ mode. We establish upper limits at 90% confidence level of $\mathcal{B}(B^{+}\to K^{*+}\nu \overline{\nu })<8\times {10}^{-5}$, $\mathcal{B}(B^0\to K^{*0}\nu \overline{\nu })<12\times {10}^{-5}$, and $\mathcal{B}(B\to K^{*}\nu \overline{\nu })<8\times {10}^{-5}$.

The reasonableness of the use of perturbative QCD notions in the region close to the scale of hadronization, i.e., below $\lesssim 1\mathrm{GeV}$ is under study. First, the interplay between higher orders of pQCD expansion and higher-twist contributions in the analysis of recent Jefferson Lab (JLab) data on the generalized Bjorken sum rule function ${\Gamma }_1^{p-n}(Q^2)$ at $0.1<Q^2<3{\mathrm{GeV}}^2$ is studied. It is shown that the inclusion of the higher-order pQCD corrections could be absorbed, with good numerical accuracy, by change of the normalization of the higher-twist terms. Second, to avoid the issue of unphysical singularity (Landau pole at $Q=\Lambda \sim 400\mathrm{MeV}$), we deal with the ghost-free analytic perturbation theory (APT) that recently proved to be an intriguing candidate for a quantitative description of light quarkonia spectra within the Bethe-Salpeter approach. The values of the twist coefficients ${\mu }_{2k}$ extracted from the mentioned data by using the APT approach provide a better convergence of the higher-twist series than with the common pQCD. As the main result, a good quantitative description of the JLab data down to $Q\simeq 350\mathrm{MeV}$ is achieved.

We present numerical and analytical studies of the equation of state of translationally invariant black hole solutions to five-dimensional gravity coupled to a single scalar. As an application, we construct a family of black holes that closely mimics the equation of state of quantum chromodynamics at zero chemical potential.

We study the effect of photon and ultralight pseudoscalar mixing on the propagation of electromagnetic radiation through the extragalactic medium. The medium is modeled as a large number of uncorrelated magnetic domains. We obtain an analytic expression for the different Stokes parameters in the limit of a small mixing angle. Stokes parameters are found to change linearly with the number of domains. We verify this result by direct numerical simulations. We use the formalism to estimate the effect of pseudoscalar-photon mixing on the cosmic microwave background (CMB) polarization. We impose limits on the model parameters consistent with CMB observations. We find that the currently allowed parameter range admits a CMB circular polarization up to order ${10}^{-7}$.

The stability under radial and vertical perturbations of circular orbits associated to particles orbiting a spherically symmetric center of attraction is studied in the context of the $n$-dimensional: the Newtonian theory of gravitation, Einstein’s general relativity, and the Einstein-Gauss-Bonnet theory of gravitation. The presence of a cosmological constant is also considered. We find that this constant as well as the Gauss-Bonnet coupling constant are crucial to have stability for $n>4$.

In the next-to-minimal supersymmetric standard model (NMSSM), the presence of light pseudoscalars can have a dramatic effect on the decays of the standard model-like Higgs boson. These pseudoscalars are naturally light if supersymmetry breaking preserves an approximate $U(1{)}_R$ symmetry, spontaneously broken when the Higgs bosons take on their expectation values. We investigate two classes of theories that possess such an approximate $U(1{)}_R$ at the mediation scale: modifications of gauge and gaugino mediation. In the models we consider, we find two disjoint classes of phenomenologically allowed parameter regions. One of these regions corresponds to a limit where the singlet of the NMSSM largely decouples. The other can give rise to a standard model-like Higgs boson with dominant branching into light pseudoscalars.

We have worked out covariant amplitudes for any two-body decay of a resonance with an arbitrary nonzero mass, which involves arbitrary integer spins in the initial and the final states. One key new ingredient for this work is the application of the total intrinsic spin operator which is given directly in terms of the generators of the Poincaré group. Using the results of this study, we show how to explore the Lorentz factors which appear naturally, if the momentum-space wave functions are used to form the covariant decay amplitudes. We have devised a method of constructing our covariant decay amplitudes, such that they lead to the Zemach amplitudes when the Lorentz factors are set to one.

In models of electroweak symmetry breaking in which the standard model fermions get their masses by mixing with composite states, it is natural to expect the top quark to show properties of compositeness. We study the phenomenological viability of having a mostly composite top. The strongest constraints are shown to mainly come from one-loop contributions to the $T$ parameter. Nevertheless, the presence of light custodial partners weakens these bounds, allowing in certain cases for a high degree of top compositeness. We find regions in the parameter space in which the $T$ parameter receives moderate positive contributions, favoring the electroweak fit of this type of model. We also study the implications of having a composite top at the LHC, focusing on the process $pp\to t\overline{t}t\overline{t}(b\overline{b})$ whose cross section is enhanced at high energies.

Towards the investigation of the full dynamics in a higher-dimensional and/or a stringy gravitational model, we present the basic equations of the Einstein-Gauss-Bonnet gravity theory. We show the $(N+1)$-dimensional version of the Arnowitt-Deser-Misner decomposition including Gauss-Bonnet terms, which shall be the standard approach to treat the space-time as a Cauchy problem. Because of the quasilinear property of the Gauss-Bonnet gravity, we find that the evolution equations can be in a treatable form in numerics. We also show the conformally transformed constraint equations for constructing the initial data. We discuss how the constraints can be simplified by tuning the powers of conformal factors. Our equations can be used both for timelike and spacelike foliations.

A conservative upper bound on the total dark matter annihilation rate can be obtained by constraining the appearance rate of the annihilation products which are hardest to detect. The production of neutrinos, via the process $\chi \chi \to \overline{\nu }\nu$, has thus been used to set a strong general bound on the dark matter annihilation rate. However, standard model radiative corrections to this process will inevitably produce photons which may be easier to detect. We present an explicit calculation of the branching ratios for the electroweak bremsstrahlung processes $\chi \chi \to \overline{\nu }\nu Z$ and $\chi \chi \to \overline{\nu }eW$. These modes inevitably lead to electromagnetic showers and further constraints on the dark matter annihilation cross section. In addition to annihilation, our calculations are also applicable to the case of dark matter decay.

We report a high-statistics measurement of the branching fraction for ${\tau }^{-}\to {\pi }^{-}{\pi }^0{\nu }_{\tau }$ and the invariant mass spectrum of the produced ${\pi }^{-}{\pi }^0$ system using $72.2{\mathrm{fb}}^{-1}$ of data recorded with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The branching fraction obtained is $(25.24\pm 0.01\pm 0.39)\%$, where the first error is statistical and the second is systematic. The unfolded ${\pi }^{-}{\pi }^0$ mass spectrum is used to determine resonance parameters for the $\rho (770)$, ${\rho }^{\prime }(1450)$, and ${\rho }^{\prime \prime }(1700)$ mesons. We also use this spectrum to estimate the hadronic ($2\pi$) contribution to the anomalous magnetic moment of the muon ($a_{\mu }^{\pi \pi }$). Our result for $a_{\mu }^{\pi \pi }$ integrated over the mass range $\sqrt{s}=2m_{\pi }-1.8\mathrm{GeV}/c^2$ is $a_{\mu }^{\pi \pi }=(523.5\pm 1.5(\exp )\pm 2.6(\mathrm{Br})\pm 2.5(\mathrm{isospin}))\times {10}^{-10}$, where the first error is due to the experimental uncertainties, the second is due to the uncertainties in the branching fractions, and the third is due to the uncertainties in the isospin-violating corrections.

We report a study of the suppressed $B$ meson decay $B^{-}\to D{K}^{-}$ followed by $D\to K^{+}{\pi }^{-}$, where $D$ indicates a $D^0$ or ${\overline{D}}^0$ state. The two decay paths interfere and provide information on the $CP$-violating angle ${\varphi }_3$. We use a data sample containing $657\times {10}^6$ $B\overline{B}$ pairs recorded at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ storage ring. We do not find significant evidence for the mode $B^{-}\to D{K}^{-}$, $D\to K^{+}{\pi }^{-}$, and set an upper limit of $r_B<0.19$, where $r_B$ is the magnitude of the ratio of amplitudes $|A(B^{-}\to {\overline{D}}^0{K}^{-})/A(B^{-}\to D^0{K}^{-})|$. The decay $B^{-}\to D{\pi }^{-}$, $D\to K^{+}{\pi }^{-}$ is also analyzed as a reference, for which we observe a signal with $6.6\sigma$ significance, and measure the charge asymmetry ${\mathcal{A}}_{D\pi }$ to be $-{0.02}_{-0.16}^{+0.15}(\mathrm{stat})\pm 0.04(\mathrm{syst})$. In addition, the ratio $\mathcal{B}(B^{-}\to D^0{K}^{-})/\mathcal{B}(B^{-}\to D^0{\pi }^{-})$ is measured to be $[6.77\pm 0.23(\mathrm{stat})\pm 0.30(\mathrm{syst})]\times {10}^{-2}$.

We analyze static properties of nucleons in the two flavor holographic QCD model of Sakai and Sugimoto described effectively by a five-dimensional $U(2)$ Yang-Mills theory with the Chern-Simons term on a curved background. The baryons are represented in this model as a soliton, which at a time slice is approximately the Belavin-Polyakov-Shvarts-Tyupkin (BPST) instanton with a fixed size. First, we construct a chiral current in four dimensions from the Noether current of local gauge transformations which are nonvanishing on the boundaries of the extra dimension. We examine this chiral current for nucleons with quantized collective coordinates to compute their charge distribution, charge radii, magnetic moments, and axial-vector coupling. Most of the results are better close to the experimental values than in the Skyrme model. We discuss the problems of our chiral current, nonuniqueness of the local gauge transformation for defining the current, and its gauge-noninvariance.

In this paper we consider the transition from the Kadanoff-Baym equations to the quantum kinetic equations and then to the Boltzmann equation in curved space-time. As one expects from general considerations, the derived equations appear to be covariant generalizations of the corresponding equations in Minkowski space-time. The formalism will be applied to test approximations commonly made in the computation of the baryon asymmetry in the leptogenesis scenario.

Stabilization of interbrane distance is analyzed in five-dimensional models with higher-order scalar kinetic terms. Equations of motion and boundary conditions for background and for scalar perturbations are presented. Conditions sufficient and (with one exception) necessary for stability are derived and discussed. It is shown that it is possible to construct stable brane configurations even without scalar potentials and cosmological constants. As a by-product we identify a large class of nonstandard boundary conditions for which the Sturm-Liouville operator is Hermitian.