We study the twist-3 distribution amplitudes for scalar mesons made up of two valence quarks based on QCD sum rules. By choosing the proper correlation functions, we derive the moments of the scalar mesons up to the first two orders. Making use of these moments, we then calculate the first two Gegenbauer coefficients for twist-3 distribution amplitudes of scalar mesons. It is found that the second Gegenbauer coefficients of scalar density twist-3 distribution amplitudes for $K_0^{*}$ and $f_0$ mesons are quite close to that for $a_0$, which indicates that the SU(3) symmetry breaking effect is tiny here. However, this effect could not be neglected for the forth Gegenbauer coefficients of scalar twist-3 distribution amplitudes between $a_0$ and $f_0$. Besides, we also observe that the first two Gegenbauer coefficients corresponding to the tensor current twist-3 distribution amplitudes for all the $a_0$, $K_0^{*}$ and $f_0$ are very small. The renormalization group evolution of condensates, quark masses, decay constants and moments are considered in our calculations. As a by-product, it is found that the masses for isospin $I=1$, $\frac{1}{2}$ scalar mesons are around $1.27\sim 1.41\mathrm{GeV}$ and $1.44\sim 1.56\mathrm{GeV}$ respectively, while the mass for isospin state composed of $\overline{s}s$ is $1.62\sim 1.73\mathrm{GeV}$.

We investigate phenomenology related to the neutral fields in supersymmetric models with an extra U(1) derived from $E_6$. Our study is concentrated on the models which have a singlino-dominated neutralino as the lightest superparticle (LSP). If such models satisfy a constraint for dark matter derived from the WMAP data, the lightest neutral Higgs scalar, a new neutral gauge field $Z^{\prime }$, and the LSP may be interesting targets for the study at the LHC. We also discuss features of the $Z^{\prime }$ in the models and its detectability at the LHC.

Gravitinos and hidden sector fields often cause a cosmological disaster in supersymmetric models. We find that a model with gravitational gauge mediation solves such a problem quite naturally. The $\mu$-problem is also absent in the model. Moreover, the abundance of gravitinos explains correct amount of dark matter of the universe. The dark matter abundance can be calculated without detailed information on the thermal history of the universe such as the reheating temperature after inflation.

In this work we estimate the differential cross section for the high energy deeply virtual Compton scattering on a photon target, ${\gamma }^{*}\gamma \to \gamma \gamma$, within the QCD dipole-dipole scattering formalism. For the phenomenology, a saturation model for the dipole-dipole cross section for two photon scattering is considered. Its robustness is supported by a good description of current accelerator data. In addition, we consider the related exclusive vector meson production processes, ${\gamma }^{*}\gamma \to V\gamma$. This analysis is focused on the light $\rho$ and $\varphi$ meson production, which produces larger cross sections. The phenomenological results are compared with the theoretical calculation using the color-dipole Balitsky-Fadin-Kuraev-Lipatov approach.

A chiral invariant Lagrangian describing the tetraquark-quarkonia interaction is considered at the leading and subleading order in the large-$N_c$ expansion. Spontaneous chiral symmetry breaking generates mixing of scalar tetraquark and quarkonia states and nonvanishing tetraquark condensates. In particular, the mixing strength is related to the decay strengths of tetraquark states into pseudoscalar mesons. The results show that scalar states below 1 GeV are mainly four-quark states and the scalars between 1 and 2 GeV quark-antiquark states, probably mixed with the scalar glueball in the isoscalar sector.

In our previous paper we applied U-spin symmetry to charmless hadronic $B^{\pm }\to M^0{M}^{\pm }$ decays for the purpose of precise extraction of the unitarity angle $\gamma$. In this paper we extend our approach to neutral $B^0$ and $B_s\to M_1{M}_2$ decays. A very important feature of this method is that no assumptions regarding relative sizes of topological decay amplitudes need to be made. As a result, this method avoids an uncontrollable theoretical uncertainty that is often related to the neglect of some topological diagrams (e.g., exchange and annihilation graphs) in quark-diagrammatic approaches. In charged $B^{\pm }$ decays, each of the four data sets, $P^0{P}^{\pm }$, $P^0{V}^{\pm }$, $V^0{P}^{\pm }$ and $V^0{V}^{\pm }$, with $P\equiv \mathrm{\text{pseudoscalar}}$ and $V\equiv \mathrm{\text{vector}}$, can be used to obtain a value of $\gamma$. Among neutral decays, only experimental data in the $B^0$, $B_s\to P^{-}{P}^{+}$ subsector is sufficient for a U-spin fit. Application of the U-spin approach to the current charged and neutral $B$ decay data yields: $\gamma =({80}_{-8}^{+6})°$. In this method, which is completely data driven, in a few years we should be able to obtain a model-independent determination of $\gamma$ with an accuracy of O(few degrees).

A study of semi-inclusive deep inelastic scattering off transversely polarized ${}^3\mathrm{He}$ is presented. The formal expressions of the Collins and Sivers contributions to the azimuthal single spin asymmetry for the production of leading pions are derived, in impulse approximation, and estimated in the kinematics of forth-coming experiments at JLab. The AV18 interaction has been used for a realistic description of the nuclear dynamics; the nucleon structure has been described by proper parametrizations of data or suitable model calculations. The initial transverse momentum of the struck quark has been properly included in the calculation. The crucial issue of extracting the neutron information from ${}^3\mathrm{He}$ data, planned to shed some light on the puzzling experimental scenario arisen from recent measurements for the proton and the deuteron, is thoroughly discussed. It is found that a model independent procedure, widely used in inclusive deep inelastic scattering to take into account the momentum and energy distributions of the bound nucleons in ${}^3\mathrm{He}$, can be applied also in the kinematics of the planned JLab experiments, although fragmentation functions, not only parton distributions, are involved. The possible role played by final state interactions in the process under investigation is addressed.

We study a model in which lepton number violation is solely triggered by a dimension 4 hard breaking term in the scalar potential. A minimal model, which contains a $SU(2)$ triplet with hypercharge $Y=2$ and a pair of singlet doubly charged scalar fields in addition to the standard model (SM) Higgs doublet, is constructed. The model is technically natural in the sense that lepton number is preserved in the limit that the hard term vanishes. SM phenomenology restricts the vacuum expectation value of the triplet scalar field $v_T<5.78\mathrm{GeV}$. Neutrino masses controlled by $v_T$ are generated at the two loop level and are naturally in the sub-eV range. In general they exhibit normal hierarchy structure. Here the neutrino mass term does not dominate neutrinoless double beta decays of nuclei. Instead the short-distance physics with doubly charged Higgs exchange gives the leading contribution. We expect weak scale singly and doubly charged Higgs bosons to make their appearances at the LHC and the ILC.

We study how the rotation of a classical magnetic field influences vacuum birefringence. In spite of the fact that solutions of the wave equation depend in a nontrivial way on the relative magnitude of the strength of vacuum birefringence and the angular rotation frequency of the magnetic field, the induced ellipticity of the light ray does not depend on the magnetic field angular rotation frequency. Hence, in contrast to recent claims, the result of the PVLAS experiment cannot be explained by conventional nonlinear quantum electrodynamics.

We explicitly calculate the induced gravity theory at the boundary of an asymptotically anti–de Sitter five dimensional Einstein gravity. We also display the action that encodes the dynamics of radial diffeomorphisms. It is found that the induced theory is a four dimensional conformal gravity plus a scalar field. This calculation confirms some previous results found by a different approach.

Cosmic rays from outer space enter the atmosphere with energies of up to ${10}^{11}\mathrm{GeV}$. The initial particle or a secondary hadron inside the shower may then interact with an air nucleon to produce nonstandard particles. In this article we study the production of new physics by high energy cosmic rays, focusing on the long-lived gluino of split-SUSY models and a weakly interacting massive particle (WIMP) working as dark matter. We first deduce the total flux of hadron events at any depth in the atmosphere, showing that secondary hadrons can not be neglected. Then we use these results to find the flux of gluinos and WIMPs that reach the ground after being produced inside air showers. We also evaluate the probability of producing these exotic particles in a single proton shower of ultrahigh energy. Finally we discuss the possible signal in current and projected experiments. While the tiny flux of WIMPs does not seem to have any phenomenological consequences, we show that the gluinos could modify substantially the profile of a small fraction of extensive air showers. In particular, they could produce a distinct signal observable at AUGER in showers of large zenith angle.

We investigate the properties of scalar and pseudoscalar mesons at finite temperature and quark chemical potential in the framework of the Nambu–Jona-Lasinio (NJL) model coupled to the Polyakov loop (PNJL model) with the aim of taking into account features of both chiral symmetry breaking and deconfinement. The mesonic correlators are obtained by solving the Schwinger-Dyson equation in the RPA approximation with the Hartree (mean field) quark propagator at finite temperature and density. In the phase of broken chiral symmetry, a narrower width for the $\sigma$ meson is obtained with respect to the NJL case; on the other hand, the pion still behaves as a Goldstone boson. When chiral symmetry is restored, the pion and $\sigma$ spectral functions tend to merge. The Mott temperature for the pion is also computed.

We study head-on collisions of boson stars in three dimensions. We consider evolutions of two boson stars which may differ in their phase or have opposite frequencies but are otherwise identical. Our studies show that these phase differences result in different late time behavior and gravitational wave output.

The null surfaces of a spacetime act as oneway membranes and can block information for a corresponding family of observers (timelike curves). Since lack of information can be related to entropy, this suggests the possibility of assigning an entropy to the null surfaces of a spacetime. We motivate and introduce such an entropy functional for any vector field in terms of a fourth-rank divergence-free tensor $P_{ab}^{cd}$ with the symmetries of the curvature tensor. Extremizing this entropy for all the null surfaces then leads to equations for the background metric of the spacetime. When $P_{ab}^{cd}$ is constructed from the metric alone, these equations are identical to Einstein’s equations with an undetermined cosmological constant (which arises as an integration constant). More generally, if $P_{ab}^{cd}$ is allowed to depend on both metric and curvature in a polynomial form, one recovers the Lanczos-Lovelock gravity. In all these cases: (a) We only need to extremize the entropy associated with the null surfaces; the metric is not a dynamical variable in this approach. (b) The extremal value of the entropy agrees with standard results, when evaluated on shell for a solution admitting a horizon. The role of the full quantum theory of gravity will be to provide the specific form of $P_{ab}^{cd}$ which should be used in the entropy functional. With such an interpretation, it seems reasonable to interpret the Lanczos-Lovelock type terms as quantum corrections to classical gravity.

We show that, as a result of nonlinear self-interactions, it is feasible, at least in light of the bounds coming from terrestrial tests of gravity, measurements of the Casimir force and those constraints imposed by the physics of compact objects, big-bang nucleosynthesis and measurements of the cosmic microwave background, for there to exist, in our Universe, one or more scalar fields that couple to matter much more strongly than gravity does. These scalar fields behave like chameleons: changing their properties to fit their surroundings. As a result these scalar fields can be not only very strongly coupled to matter, but also remain relatively light over solar-system scales. These fields could also be detected by a number of future experiments provided they are properly designed to do so. These results open up an altogether new window, which might lead to a completely different view of the rôle played by light scalar fields in particle physics and cosmology.

TeV $\gamma$-rays may provide significant information about high energy astrophysical accelerators. Such $\gamma$-rays can result from the photo-de-excitation of PeV nuclei after their parents have undergone photo-disintegration in an environment of ultraviolet photons. This process is proposed as a candidate explanation of the recently discovered HEGRA source at the edge of the Cygnus OB2 association. The Lyman-$\alpha$ background is provided by the rich $\mathrm{O}$ and $\mathrm{B}$ stellar environment. It is found that (1) the HEGRA flux can be obtained if there is efficient acceleration at the source of lower energy nuclei; (2) the requirement that the Lorentz-boosted ultraviolet photons can excite the giant dipole resonance implies a strong suppression of the $\gamma$-ray spectrum compared to an $E_{\gamma }^{-2}$ behavior at energies $\lesssim 1\mathrm{TeV}$ (some of these energies will be probed by the upcoming GLAST mission); (3) a TeV neutrino counterpart from neutron decay following helium photo-disintegration will be observed at IceCube only if a major proportion of the kinetic energy budget of the Cygnus OB2 association is expended in accelerating nuclei.

We calculate the main observables in $B_{u,d}\to (\rho ,\omega ,K^{*})\gamma$ and $B_s\to ({\overline{K}}^{*},\varphi )\gamma$ decays, i.e. branching ratios and $CP$ and isospin asymmetries. We include QCD factorization results and also the dominant contributions beyond QCD factorization, namely, long-distance photon emission and soft-gluon emission from quark loops. All contributions beyond QCD factorization are estimated from light-cone sum rules. We devise, in particular, a method for calculating soft-gluon emission, building on earlier ideas developed for analogous contributions in nonleptonic decays. Our results are relevant for new-physics searches at the $B$ factories, CERN LHC and a future superflavor factory. Using current experimental data, we also extract $|V_{td}/V_{ts}|$ and the angle $\gamma$ of the unitarity triangle. We give detailed tables of theoretical uncertainties of the relevant quantities which facilitates future determinations of these Cabibbo-Kobayashi-Maskawa parameters from updated experimental results.

We explore the phase structure induced by closed string tachyon condensation of toric nonsupersymmetric conifold-like singularities described by an integral charge matrix $Q=(n_1{n}_2-n_3-n_4)$, $n_i>0$, $\sum _i{Q}_i\ne 0$, initiated by Narayan [J. High Energy Phys. 03 (2006) 036]. Using gauged linear sigma model renormalization group flows and toric geometry techniques, we see a cascadelike phase structure containing decays to lower order conifold-like singularities, including, in particular, the supersymmetric conifold and the $Y^{pq}$ spaces. This structure is consistent with the Type II GSO projection obtained previously for these singularities. Transitions between the various phases of these geometries include flips and flops.

We consider the interaction of a cylindrical graphene sheet with a dielectric half space and with a flat graphene sheet by a generalization of the method of functional determinants. We confirm the proximity force approximation (PFA) for these configurations and calculate the first correction beyond PFA. This can be considered as a generalization of the Lifshitz formula to such configurations.