Using the most general form of the interpolating current of the baryons, the strong coupling constants of the light vector mesons with the octet baryons are calculated within the light cone QCD sum rules. The $SU(3{)}_f$ symmetry breaking effects are taken into account in the calculations. It is shown that each of the electric and magnetic coupling constants can be described in terms of three universal functions. A detailed comparison of the results of this work on aforementioned couplings with the existing theoretical results is presented.

We investigate the rare semileptonic decays $B_s\to [f_0(980),K_0^{*}(1430)]l^{+}{l}^{-}$, ($l=e$, $\mu$, $\tau$), and $B_s\to [f_0(980),K_0^{*}(1430)]\nu \overline{\nu }$ in the framework of the three-point QCD sum rules. These decays are important to study because the $f_0(980)$ and $K_0^{*}(1430)$ are the scalar mesons with total spin 0 and even parity and the quark content of them are still controversial in high energy physics. These rare decays occur at loop level by electroweak penguin and weak box diagrams in the standard model via the flavor changing neutral current transitions of $b\to d$, $s$, and not allowed by tree level. Considering the effective contributions of the nonperturbative parts of the correlation function, we calculate the relevant form factors of these transitions. The branching fractions and longitudinal lepton polarization asymmetry are also investigated.

The recent measurement on the decay constant of $D_s$ shows a discrepancy between theory and experiment. We study the leptonic and semileptonic decays of $D$ and $D_s$ simultaneously within the standard model by employing a light-front quark model. There is space by tuning phenomenological parameters which can explain the “$f_{D_s}$ puzzle” and do not contradict other experiments on the semileptonic decays. We also investigate the leptonic decays of $D$ and $D_s$ with a new physics scenario, unparticle physics. The unparticle effects induce a constructive interference with the standard model contribution. The nontrivial phase in unparticle physics could produce direct $CP$ violation which may distinguish it from other new physics scenarios.

The strongly coupled standard model predicts a rich spectrum of excited states at the Fermi scale. We study the first radial excitations of the vector-bosons. The inclusion of these new states affects the low-energy phenomenology of the model. We put constraints on the effective couplings by performing a global fit with the electroweak observables, and we find that the excitations have to be rather decoupled from the low-energy states.

The behavior of photons in the presence of Lorentz and $CPT$ violation is studied. Allowing for operators of arbitrary mass dimension, we classify all gauge-invariant Lorentz- and $CPT$-violating terms in the quadratic Lagrange density associated with the effective photon propagator. The covariant dispersion relation is obtained, and conditions for birefringence are discussed. We provide a complete characterization of the coefficients for Lorentz violation for all mass dimensions via a decomposition using spin-weighted spherical harmonics. The resulting nine independent sets of spherical coefficients control birefringence, dispersion, and anisotropy in the photon propagator. We discuss the restriction of the general theory to various special models, including among others the minimal standard-model extension, the isotropic limit, the case of vacuum propagation, the nonbirefringent limit, and the vacuum-orthogonal model. The transformation of the spherical coefficients for Lorentz violation between the laboratory frame and the standard Sun-centered frame is provided. We apply the results to various astrophysical observations and laboratory experiments. Astrophysical searches of relevance include studies of birefringence and of dispersion. We use polarimetric and dispersive data from gamma-ray bursts to set constraints on coefficients for Lorentz violation involving operators of dimensions four through nine, and we describe the mixing of polarizations induced by Lorentz and $CPT$ violation in the cosmic-microwave background. Laboratory searches of interest include cavity experiments. We present the general theory for searches with cavities, derive the experiment-dependent factors for coefficients in the vacuum-orthogonal model, and predict the corresponding frequency shift for a circular-cylindrical cavity.

We study composite systems of light ($\rho$ and $\omega$) and heavy ($D^{*}$) vector mesons by using the interaction within the hidden gauge formalism. We find a strong attraction in the isospin, spin channels $(I,S)=(1/2,0)$, $(1/2,1)$, and $(1/2,2)$ with positive parity. The attraction is large enough to strongly bind these mesons in states with these quantum numbers, leading to states which can be identified with $D_2^{*}(2460)$ and probably with $D^{*}(2640)$, the last one without experimental spin and parity assignment. In the case of $I=3/2$, one obtains repulsion and thus, no exotic mesons in this sector are generated in the approach.

In the standard model, we reinvestigate the rare decay $B\to \varphi \pi$, which is viewed as an ideal probe to detect the new physics signals. We find that the tiny branching ratio in the naive factorization can be dramatically enhanced by the radiative corrections and the $\omega -\varphi$ mixing effect, while the long-distance contributions are negligibly small. Assuming the Cabibbo-Kobayashi-Maskawa angle $\gamma =(58.6\pm 10)°$ and the mixing angle $\theta =-(3.0\pm 1.0)°$, we obtain the branching ratios of $B\to \varphi \pi$ as $\mathrm{Br}(B^{\pm }\to \varphi {\pi }^{\pm })=({3.2}_{-0.7+1.8}^{+0.8-1.2})\times {10}^{-8}$ and $\mathrm{Br}(B^0\to \varphi {\pi }^0)=({6.8}_{-0.3+1.0}^{+0.3-0.7})\times {10}^{-9}$. If the future experiment reports a branching ratio of $(0.2–0.5)\times {10}^{-7}$ for $B^{-}\to \varphi {\pi }^{-}$ decay, it may not be a clear signal for any new physics scenario. In order to discriminate the large new physics contributions from those due to the $\omega -\varphi$ mixing, we propose to measure the ratio of branching fractions of the charged and neutral $B$ decay channel. We also study the direct $CP$ asymmetries of these two channels: $(-{8.0}_{-1.0-0.1}^{+0.9+1.5})\%$ and $(-{6.3}_{+0.7-2.5}^{-0.5+2.5})\%$ for $B^{\pm }\to \varphi {\pi }^{\pm }$ and $B^0\to \varphi {\pi }^0$, respectively. These asymmetries are dominated by the mixing effect.

We calculate the coupling constants between the light vector mesons and heavy mesons within the framework of the light-cone QCD sum rule in the leading order of heavy quark effective theory. The sum rules are very stable with the variations of the Borel parameter and the continuum threshold. The extracted couplings will be useful in the study of the possible heavy meson molecular states. They may also helpful in the interpretation of the proximity of $X(3872)$, $Y(4260)$, and $Z(4430)$ to the threshold of two charmed mesons through the couple-channel mechanism.

We report on the next-to-leading order (NLO) QCD computation of top-quark pair production in association with a photon at the Fermilab Tevatron RUN II and CERN Large Hadron Collider. We describe the impact of the complete NLO QCD radiative corrections to this process, and provide the predictions of the leading order (LO) and NLO integrated cross sections, distributions of the transverse momenta of the top quark and photon for the LHC and Tevatron, and the LO and NLO forward-backward top-quark charge asymmetries for the Tevatron. We investigate the dependence of the LO and NLO cross sections on the renormalization/factorization scale, and find the scale dependence of the LO cross section is obviously improved by the NLO QCD corrections. The $K$-factor of the NLO QCD correction is 0.977(1.524) for the Tevatron (LHC).

Transverse parton momentum dependent distribution functions (TMDs) of the nucleon are studied in a covariant model, which describes the intrinsic motion of partons in terms of a covariant momentum distribution. The consistency of the approach is demonstrated, and model relations among TMDs are studied. As a by-product it is shown how the approach allows to formulate the nonrelativistic limit.

Ohmic currents induced prior to decoupling are investigated in a standard transport model accounting both for the expansion of the background geometry as well as of its relativistic inhomogeneities. The relative balance of the Ohmic electric fields in comparison with the Hall and thermoelectric contributions is specifically addressed. The impact of the Ohmic currents on the evolution of curvature perturbations is discussed numerically and it is shown to depend explicitly upon the evolution of the conductivity.

We consider a theory of gravity in which a symmetric two-index tensor in Minkowski spacetime acquires a vacuum expectation value (vev) via a potential, thereby breaking Lorentz invariance spontaneously. When the vev breaks all the generators of the Lorentz group, six Goldstone modes emerge, two linear combinations of which have properties that are identical to those of the graviton in general relativity. Integrating out massive modes yields an infinite number of Lorentz-violating radiative-correction terms in the low-energy effective Lagrangian. We examine a representative subset of these terms and show that they modify the dispersion relation of the two propagating graviton modes such that their phase velocity is direction dependent. If the phase velocity of the Goldstone gravitons is subluminal, cosmic rays can emit gravi-Cherenkov radiation, and the detection of high-energy cosmic rays can be used to constrain these radiative-correction terms. Test particles in the vicinity of the Goldstone gravitons undergo longitudinal oscillations in addition to the usual transverse oscillations as predicted by general relativity. Finally, we discuss the possibility of having vevs that do not break all six generators and examine in detail one such theory.

Classical isometrodynamics is quantized in the Euclidean plus axial gauge. The quantization is then generalized to a broad class of gauges and the generating functional for the Green functions of quantum isometrodynamics (QID) is derived. Feynman rules in covariant Euclidean gauges are determined and QID is shown to be renormalizable by power counting. Asymptotic states are discussed and new quantum numbers related to the “inner” degrees of freedom introduced. The one-loop effective action in a Euclidean background gauge is formally calculated and shown to be finite and gauge invariant after renormalization and a consistent definition of the arising inner space momentum integrals. Pure QID is shown to be asymptotically free for all dimensions of inner space $D$, whereas QID coupled to the standard model fields is not asymptotically free for $D\le 7$. Finally nilpotent Becchi-Rouet-Stora-Tyutin (BRST) transformations for isometrodynamics are derived along with the BRST symmetry of the theory and a sketch of the general proof of renormalizability for QID is given.

A generalization of non-Abelian gauge theories of compact Lie groups is developed by gauging the noncompact group of volume-preserving diffeomorphisms of a $D$-dimensional space ${\mathbf{R}}^D$. This group is represented on the space of fields defined on ${\mathbf{M}}^4\times {\mathbf{R}}^D$. As usual the gauging requires the introduction of a covariant derivative, a gauge field, and a field strength operator. An invariant and minimal gauge field Lagrangian is derived. The classical field dynamics and the conservation laws of the new gauge theory are developed. Finally, the theory’s Hamiltonian in the axial gauge and its Hamiltonian field dynamics are derived.

We construct a plane symmetric, standing gravitational wave for a domain wall plus a massless scalar field. The scalar field can be associated with a fluid which has the properties of “stiff” matter, i.e., matter in which the speed of sound equals the speed of light. Although domain walls are observationally ruled out in the present era, the solution has interesting features which might shed light on the character of exact nonlinear wave solutions to Einstein’s equations. Additionally this solution may act as a template for higher dimensional “brane-world” model standing waves.

We analyze, within the framework of unified brane gravity, the weak-field perturbations caused by the presence of matter on a 3-brane. Although deviating from the Randall-Sundrum approach, the masslessness of the graviton is still preserved. In particular, the four-dimensional Newton force law is recovered, but serendipitously, the corresponding Newton constant is shown to be necessarily lower than the one which governs Friedmann-Robertson-Walker cosmology. This has the potential to puzzle out cosmological dark matter. A subsequent conjecture concerning galactic dark matter follows.

We develop the necessary ingredients for the construction of realistic models with warped universal extra dimensions. Our investigations are based on the seven-dimensional (7D) spacetime ${\mathrm{AdS}}_5\times T^2/Z_2$ and we derive the Kaluza-Klein (KK) spectra for gravitons, bulk vectors, and the TeV brane localized Higgs boson. We show that, starting with a massive 7D fermion, one may obtain a single chiral massless mode whose profile is readily localized towards the Planck or TeV brane. This allows one to place the standard model fermions in the bulk and construct models of flavor as in Randall-Sundrum models. Our solution also admits the familiar KK parity of models with universal extra dimensions so that the lightest odd KK state is stable and may be a dark matter candidate. As an additional feature the ${\mathrm{AdS}}_5$ warping ensures that the excited modes on the torus, including the dark matter candidate, appear at TeV energies (as is usually assumed in models with universal extra dimensions) even though the Planck scale sets the dimensions for the torus.

We investigate the phase space of a quintessence theory governed by a generalized version of the DBI action, using a combination of numeric and analytic methods. The additional degrees of freedom lead to a vastly richer phase-space structure, where the field covers the full equation of state parameter space: $-1\le \omega \le 1$. We find many nontrivial solution curves to the equations of motion which indicate that DBI quintessence is an interesting candidate for a viable $k$-essence model.

Current cosmological observations indicate a preference for a cosmological constant that is drastically smaller than what can be explained by conventional particle physics. The causal entropic principle (Bousso et al.) provides an alternative approach to anthropic attempts to predict our observed value of the cosmological constant by calculating the entropy created within a causal diamond. We have extended this work to use the causal entropic principle to predict the preferred curvature within the “multiverse.” We have found that values larger than ${\rho }_k=40{\rho }_m$ are disfavored by more than 99.99% peak value at ${\rho }_{\Lambda }=7.9\times {10}^{-123}$ and ${\rho }_k=4.3{\rho }_m$ for open universes. For universes that allow only positive curvature or both positive and negative curvature, we find a correlation between curvature and dark energy that leads to an extended region of preferred values. Our universe is found to be disfavored to an extent depending on the priors on curvature. We also provide a comparison to previous anthropic constraints on open universes and discuss future directions for this work.