We present a new calculation, in the nonrelativistic QCD (NRQCD) factorization formalism, of the relativistic corrections to the double-charmonium cross section $\sigma [e^{+}{e}^{-}\to J/\psi +{\eta }_c]$ at the energy of the Belle and BABAR experiments. In comparison with previous work, our calculation contains several refinements. These include the use of the improved results for the nonperturbative NRQCD matrix elements, the resummation of a class of relativistic corrections, the use of the vector-meson-dominance method to calculate the fragmentation contribution to the pure QED amplitude, the inclusion of the effects of the running of $\alpha$, and the inclusion of the contribution that arises from the interference between the relativistic corrections and the corrections of next-to-leading order in ${\alpha }_s$. We also present a detailed estimate of the theoretical uncertainty. We conclude that the discrepancy between the theoretical prediction for $\sigma [e^{+}{e}^{-}\to J/\psi +{\eta }_c]$ and the experimental measurements has been resolved.

We present a new computation of $S$-wave color-singlet nonrelativistic QCD matrix elements for the $J/\psi$ and the ${\eta }_c$. We compute the matrix elements of leading order in the heavy-quark velocity $v$ and the matrix elements of relative order $v^2$. Our computation is based on the electromagnetic decay rates of the $J/\psi$ and the ${\eta }_c$ and on a potential model that employs the Cornell potential. We include relativistic corrections to the electromagnetic decay rates, resumming a class of corrections to all orders in $v$, and find that they significantly increase the values of the matrix elements of leading order in $v$. This increase could have important implications for theoretical predictions for a number of quarkonium decay and production processes. The values that we find for the matrix elements of relative order $v^2$ are somewhat smaller than the values that one obtains from estimates that are based on the velocity-scaling rules of nonrelativistic QCD.

Fluctuations of chromodynamic fields in the collisionless quark-gluon plasma are found as a solution of the initial value linearized problem. The plasma initial state is on average colorless, stationary, and homogeneous. When the state is stable, the initial fluctuations decay exponentially and in the long-time limit a stationary spectrum of fluctuations is established. For the equilibrium plasma it reproduces the spectrum which is provided by the fluctuation-dissipation relation. Fluctuations in the unstable plasma, where the memory of initial fluctuations is not lost, are also discussed.

The influence of quantized electromagnetic fields on a nonrelativistic charged particle moving near a conducting plate is studied. We give a field-theoretic derivation of the nonlinear, non-Markovian Langevin equation of the particle by the method of Feynman-Vernon influence functional. This stochastic approach incorporates not only the stochastic noise manifested from electromagnetic vacuum fluctuations, but also dissipation backreaction on a charge in the form of the retarded Lorentz forces. Since the imposition of the boundary is expected to anisotropically modify the effects of the fields on the evolution of the particle, we consider the motion of a charge undergoing small-amplitude oscillations in the direction either parallel or normal to the plane boundary. Under the dipole approximation for nonrelativistic motion, velocity fluctuations of the charge are found to grow linearly with time in the early stage of the evolution at the rather different rate, revealing strong anisotropic behavior. They are then asymptotically saturated as a result of the fluctuation-dissipation relation, and the same saturated value is found for the motion in both directions. The observational consequences are discussed.

A discrepancy between the anomaly mediated supersymmetry breaking (AMSB) gaugino mass calculated from the work of Kaplunovsky and Louis (hep-th/9402005) (KL) and other calculations in the literature is explained, and it is argued that the KL expression is the correct one relevant to the Wilsonian action. Furthermore it is argued that the AMSB contribution to the squark and slepton masses should be replaced by the contribution pointed out by Dine and Seiberg (DS) which has nothing to do with Weyl anomalies. This is not in general equivalent to the AMSB expression, and it is shown that there are models in which the usual AMSB expression would vanish but the DS one is nonzero. In fact the latter has aspects of both AMSB and gauge mediated supersymmetry (SUSY) breaking. In particular like the latter, it gives positive squared masses for sleptons.

In this paper, we present topological black holes of third order Lovelock gravity in the presence of cosmological constant and nonlinear electromagnetic Born-Infeld field. Depending on the metric parameters, these solutions may be interpreted as black hole solutions with inner and outer event horizons, an extreme black hole or naked singularity. We investigate the thermodynamics of asymptotically flat solutions and show that the thermodynamic and conserved quantities of these black holes satisfy the first law of thermodynamic. We also endow the Ricci flat solutions with a global rotation and calculate the finite action and conserved quantities of these class of solutions by using the counterterm method. We compute the entropy through the use of the Gibbs-Duhem relation and find that the entropy obeys the area law. We obtain a Smarr-type formula for the mass as a function of the entropy, the angular momenta, and the charge, and compute temperature, angular velocities, and electric potential and show that these thermodynamic quantities coincide with their values which are computed through the use of geometry. Finally, we perform a stability analysis for this class of solutions in both the canonical and the grand-canonical ensemble and show that the presence of a nonlinear electromagnetic field and higher curvature terms has no effect on the stability of the black branes, and they are stable in the whole phase space.

In this paper we only focus on the quintessence models in which the variation of the quintessence is less than the Planck scale. It provides a theoretical constraint on the equation of state parameter for the quintessence. In some cases our results are more stringent than the constraints from the present experiments.

We study a two-parameter family of exactly solvable inflation models with variable sound speed, and derive a corresponding exact expression for the spectrum of curvature perturbations. We generalize this expression to the slow-roll case, and derive an approximate expression for the scalar spectral index valid to second order in slow roll. We apply the result to the case of Dirac-Born-Infeld inflation, and show that for certain choices of slow-roll parameters, the Bunch-Davies limit (a) does not exist, or (b) is sensitive to stringy physics in the bulk, which in principle can have observable signatures in the primordial power spectrum.

We construct a family of viable scalar-tensor models of dark energy (DE) which possess a phase of late-time acceleration preceded by a standard matter era, while at the same time satisfying the local gravity constraints (LGC). The coupling $Q$ between the scalar field and the nonrelativistic matter in the Einstein frame is assumed to be constant in our scenario, which is a generalization of $f(R)$ gravity theories corresponding to the coupling $Q=-1/\sqrt{6}$. We find that these models can be made compatible with local gravity constraints even when $|Q|$ is of the order of unity through a chameleon mechanism, if the scalar-field potential is chosen to have a sufficiently large mass in the high-curvature regions. We show that these models generally lead to the divergence of the equation of state of DE, which occurs at smaller redshifts as the deviation from the $\Lambda \mathrm{CDM}$ model becomes more significant. We also study the evolution of matter density perturbations and employ them to place bounds on the coupling $|Q|$ as well as model parameters of the field potential from observations of the matter power spectrum and the cosmic microwave background (CMB) anisotropies. We find that, as long as $|Q|$ is smaller than the order of unity, there exist allowed parameter regions that are consistent with both observational and local gravity constraints.

The effects of a type of regularization for finite temperatures on the restoration of chiral and axial symmetries are investigated within the SU(3) Nambu-Jona-Lasinio model. The regularization consists in using an infinite cutoff in the integrals that are convergent at finite temperature, a procedure that allows one to take into account the effects of high momentum quarks at high temperatures. It is found that the critical temperature for the phase transition is closer to lattice results than the one obtained with the conventional regularization, and the restoration of chiral and axial symmetries, signaled by the behavior of several observables, occurs simultaneously and at a higher temperature. The restoration of the axial symmetry appears as a natural consequence of the full recovering of the chiral symmetry that was dynamically broken. By using an additional ansatz that simulates instanton suppression effects, by means of a convenient temperature dependence of the anomaly coefficient, we found that the restoration of U(2) symmetry is shifted to lower values, but the dominant effect at high temperatures comes from the new regularization that enhances the decrease of quark condensates, especially in the strange sector.

The observation of the Egret experiment of an excess of diffuse gamma rays with energies above $E_{\gamma }=1\mathrm{GeV}$ has previously been interpreted in the context of the minimal supergravity model (mSUGRA) as coming from neutralino annihilation into mainly $b$-quarks in the galactic halo, with neutralino mass in the vicinity of 50–70 GeV. We observe that, in order to obtain the correct relic abundance of neutralinos in accord with WMAP measurements, the corresponding neutralino-proton direct detection (DD) rates should be in excess of recent limits from the Xenon-10 collaboration. While it does not appear possible to satisfy the Egret, WMAP, and Xenon-10 constraints simultaneously within the mSUGRA model, we find that it is easily possible in models with nonuniversal Higgs soft masses (NUHM). In either case, gluino pair production from $m_{\tilde{g}}\sim 400–500\mathrm{GeV}$ should occur at large rates at the CERN LHC, and a gluino pair production signal should be visible with just $0.1{\mathrm{fb}}^{-1}$ of integrated luminosity. The NUHM interpretation predicts a rather light spectrum of heavy Higgs bosons with $m_A\sim 140–200\mathrm{GeV}$ over the whole parameter space which would interpret Egret data. Spin-independent DD rates are predicted to be just above ${10}^{-8}\mathrm{pb}$, within range of the next round of direct dark matter detection experiments.

In the next-to-minimal supersymmetric model (NMSSM) a light $CP$-odd Higgs boson is so far allowed by current experiments, which, together with a large $\tan \beta$, may greatly enhance the rare dileptonic decays $B\to X_s{\ell }^{+}{\ell }^{-}$ and $B_s\to {\ell }^{+}{\ell }^{-}\gamma$. We examine these decays paying special attention to the new operator allowed by the light $CP$-odd Higgs boson. We find that in the parameter space allowed by current experiments like CERN LEP II and $b\to s\gamma$, the branching ratios of these rare decays can be greatly enhanced, and thus the existing experimental data on $B\to X_s{\mu }^{+}{\mu }^{-}$ can further stringently constrain the parameter space (especially the region with a superlight $CP$-odd Higgs boson and large $\tan \beta$). In the surviving parameter space we give the predictions for other dileptonic decay branching ratios and also show the results for the forward-backward asymmetry.

The $K^{+}{K}^{+}$ scattering length is calculated in fully-dynamical lattice QCD with domain-wall valence quarks on the MILC asqtad-improved gauge configurations with rooted-staggered sea quarks. Three-flavor mixed-action chiral perturbation theory at next-to-leading order, which includes the leading effects of the finite lattice spacing, is used to extrapolate the results of the lattice calculation to the physical value of $m_{K^{+}}/f_{K^{+}}$. We find $m_{K^{+}}{a}_{K^{+}{K}^{+}}=-0.352\pm 0.016$, where the statistical and systematic errors have been combined in quadrature.

The naive time-reversal-odd (“$T$-odd”) parton distribution $h_1^{\perp }$, the so-called Boer-Mulders function, for both up ($u$) and down ($d$) quarks is considered in the diquark spectator model. While the results of different articles in the literature suggest that the signs of the Boer-Mulders function in semi-inclusive deep inelastic scattering (SIDIS) for both flavors $u$ and $d$ are the same and negative, a previous calculation in the diquark spectator model found that $h_1^{\perp (u)}$ and $h_1^{\perp (d)}$ have different signs. The flavor dependence is of significance for the analysis of the azimuthal $\cos (2\varphi )$ asymmetries in unpolarized SIDIS and Drell-Yan processes, as well as for the overall physical understanding of the distribution of transversely polarized quarks in unpolarized nucleons. We find substantial differences with previous work. In particular, we obtain half and first moments of the Boer-Mulders function that are negative over the full range in Bjorken $x$ for both the $u$ and $d$ quarks. In conjunction with the Collins function, we then predict the $\cos (2\varphi )$ azimuthal asymmetry for ${\pi }^{+}$ and ${\pi }^{-}$ in this framework. We also find that the Sivers $u$ and $d$ quarks are negative and positive, respectively. As a by-product of the formalism, we calculate the chiral-odd but “$T$-even” function $h_{1L}^{\perp }$, which allows us to present a prediction for the single-spin asymmetry $A_{UL}^{\sin (2\varphi )}$ for a longitudinally polarized target in SIDIS.

We study the long distance interaction for hybrid hadrons, with a static gluon, a quark and an antiquark with lattice QCD techniques. A Wilson loop adequate to the static hybrid three-body system is developed and, using a ${24}^3\times 48$ periodic lattice with $\beta =6.2$ and $a\sim 0.072\mathrm{fm}$, two different geometries for the gluon-quark segment and the gluon-antiquark segment are investigated. When these segments are perpendicular, the static potential is compatible with confinement realized with a pair of fundamental strings, one linking the gluon to the quark and another linking the same gluon to the antiquark. When the segments are parallel and superposed, the total string tension is larger and agrees with the Casimir scaling measured by Bali. This can be interpreted with a type-II superconductor analogy for the confinement in QCD, with repulsion of the fundamental strings.

We present searches for the leptonic decays $B^{+}\to {\ell }^{+}\nu$ and the lepton flavor violating decays $B^0\to {\ell }^{\pm }{\tau }^{\mp }$, where $\ell =e$, $\mu$, with data collected by the BABAR experiment at SLAC. This search demonstrates a novel technique in which we fully reconstruct the accompanying $\overline{B}$ in ${\rm Y}(4S)\to B\overline{B}$ events, and look for a monoenergetic lepton from the signal $B$ decay. The signal yield is extracted from a fit to the signal lepton candidate momentum distribution in the signal $B$ rest frame. Using a data sample of approximately $378\times {10}^6$ $B\overline{B}$ pairs ($342{\mathrm{fb}}^{-1}$), we find no evidence of signal in any of the decay modes. Branching fraction upper limits of $\mathcal{B}(B^{+}\to e^{+}\nu )<5.2\times {10}^{-6}$, $\mathcal{B}(B^{+}\to {\mu }^{+}\nu )<5.6\times {10}^{-6}$, $\mathcal{B}(B^0\to e^{+}{\tau }^{-})<2.8\times {10}^{-5}$ and $\mathcal{B}(B^0\to {\mu }^{+}{\tau }^{-})<2.2\times {10}^{-5}$, are obtained at 90% confidence level.

We show that the rate for upward showers from an isotropic cosmic neutrino flux at neutrino telescopes like IceCube is independent of the neutrino-nucleon cross section. For bins that span a relatively narrow range in energy, neither scaling the cross section, nor changing its power-law energy behavior affects the upward shower rate, which depends only on the flux. The neutrino flux can be completely known since its spectral shape can be determined by comparing the rates in neighboring bins. We also show that the downward shower rate varies linearly with cross section with a proportionality constant determined by the energy dependence of the cross section, independent of the power-law behavior of the flux. The normalization and energy dependence of the cross section can be found by comparing the downward rates in neighboring bins.

We find new non-Abelian flux tube solutions in a model of $N_f$ scalar fields in the fundamental representation of $SU(N)\times U(1)$ with $N\le N_f$ (the “extended non-Abelian Higgs model”), and study their main properties. Among the solutions there are spinning strings as well as superconducting ones. The solutions exist only in a nontrivial domain of the parameter space defined by the ratio between the $SU(N)$ and $U(1)$ coupling constants, the scalar self-interaction coupling constants, the magnetic fluxes (Abelian as well as non-Abelian) and the “twist parameter” which is a nontrivial relative phase of the Higgs fields.

The combinatorial problem of counting the black hole quantum states within the isolated horizon framework in loop quantum gravity is analyzed. A qualitative understanding of the origin of the band structure shown by the degeneracy spectrum, which is responsible for the black hole entropy quantization, is reached. Even when motivated by simple considerations, this picture allows to obtain analytical expressions for the most relevant quantities associated to this effect.

This investigation follows up the suggestion that the equation of state for superconducting cosmic strings provided by Witten’s prototype biscalar field model can be well represented by an effective Lagrangian of simple logarithmic form depending on only 3 independent parameters. The numerical work described here confirms the validity of this approximation and initiates the evaluation of the 3 required parameters, as functions of the masses and other parameters specifying the underlying $\mathrm{U}(1)\times \mathrm{U}(1)$ scalar field model in the limit for which the relevant gauge coupling constants are small. In this limit, subject to calibration of the relevant length and mass scales, the scalar field model is characterized by just 3 dimensionless ratios which (in order to provide conducting strings) must be subject to three inequalities (of which two have obvious analytic expressions). It is found here that when all three of these inequalities are satisfied by a reasonably large margin, there is a simple empirical formula that can be used to provide a fairly accurate prescription for the algebraic dependence on these 3 dimensionless ratios of the 3 parameters required for the logarithmic equation of state.