Next-to-leading-order QCD corrections to $J/\psi$ plus ${\eta }_c$ production in $e^{+}{e}^{-}$ annihilation at $\sqrt{s}=10.6\mathrm{GeV}$ are calculated in this paper, and an analytic result is obtained. By choosing proper physical parameters, a $K$ factor (ratio of next-to-leading order to LO) of about 2, which is in agreement with the result in Y.-J. Zhang, Y.-j. Gao, and K.-T. Chao, Phys. Rev. Lett. 96, 092001 (2006), is obtained. The plot of the $K$ factor vs the center-of-mass energy $\sqrt{s}$ shows that it is more difficult to obtain a convergent result from the perturbative QCD without resummation of $\ln (s/m_c^2)$ terms as the $\sqrt{s}$ becomes larger.

We consider gravity in the system consisting of the Bogomol’nyi-Prasad-Sommerfield (BPS) $D3$-brane embedded in a flat background geometry, produced by the solutions of supergravity. The effective action for this system is represented by the sum of the Hilbert-Einstein and Dirac-Born-Infeld actions. We derive the Wheeler-DeWitt equation for this system and obtain analytical solutions in some special cases. We also calculate the tunneling probability from the Planckian size of the $D3$-brane to the classical regime.

We compute the one-loop corrected effective Lagrangian for the neutralino-neutralino-neutral Higgs interactions ${\chi }_{\ell }^0{\chi }_k^0{H}_m^0$. The analysis completes the previous analyses where similar corrections were computed for the $\overline{f}f{H}_m^0$ couplings, where $f$ stands for standard model quarks and leptons and for the chargino-chargino-neutral Higgs couplings ${\chi }_l^{+}{\chi }_k^{-}{H}_m^0$ within the minimal supersymmetric standard model. The effective one-loop Lagrangian is then applied to the computation of the neutral Higgs decays. The sizes of the supersymmetric loop corrections of the neutral Higgs decay widths into ${\chi }_{\ell }^0{\chi }_k^0$ ($\ell =1$, 2, 3, 4; $k=1$, 2, 3, 4) are investigated and the supersymmetric loop correction is found to be in the range of $\sim 10\%$ in significant regions of the parameter space. By including the loop corrections of the other decay channels $\overline{b}b$, $\overline{t}t$, $\overline{\tau }\tau$, $\overline{c}c$, and ${\chi }_i^{-}{\chi }_j^{+}$ ($i=1$, 2; $j=1$, 2), the corrections to branching ratios for $H_m^0\to {\chi }_{\ell }^0{\chi }_k^0$ can reach as high as 50%. The effects of $CP$ phases on the branching ratio are also investigated. A discussion of the implications of the analysis for colliders is given.

We study D- and DF-strings in a $\mathrm{D}3\overline{\mathrm{D}}3$ system by using Dirac-Born-Infeld type action. In the presence of an electric flux from the transverse direction, we discuss gravitating thick D-string solutions of a spatial manifold, ${\mathrm{S}}^2\times {\mathrm{R}}^1$, in which straight D-strings stretched along the ${\mathrm{R}}^1$ direction are attached to the south and north poles of the two-sphere. There is a horizon along its equator, which means the structure of black strings is formed. We also discuss the BPS limit for thin parallel D- and DF-strings in both flat and curved spacetime. We obtain the BPS sum rule for an arbitrarily-separated multistring configuration with a Gaussian type tachyon potential. At the site of each thin BPS D(F)-string, the pressure takes a finite value. We find that there exists a maximum deficit angle $\pi$ in the conical geometry induced by thin BPS D- and DF-strings.

Matched asymptotic expansion is a useful technique in general relativity and other fields whenever interaction takes place between physics at two different length scales. Here matched asymptotic expansion is argued to be equivalent quite generally to classical effective field theory (CLEFT) where one (or more) of the zones is replaced by an effective theory whose terms are organized in order of increasing irrelevancy, as demonstrated by Goldberger and Rothstein in a certain gravitational context. The CLEFT perspective has advantages as the procedure is clearer, it allows a representation via Feynman diagrams, and divergences can be regularized and renormalized in standard field theoretic methods. As a side product we obtain a wide class of classical examples of regularization and renormalization, concepts which are usually associated with quantum field theories. We demonstrate these ideas through the thermodynamics of caged black holes, both simplifying the nonrotating case, and computing the rotating case. In particular we are able to replace the computation of six two-loop diagrams by a single factorizable two-loop diagram, as well as compute certain new three-loop diagrams. The results generalize to arbitrary compactification manifolds. For caged rotating black holes we obtain the leading correction for all thermodynamic quantities. The angular momentum is found to nonrenormalize at leading order.

A Hamiltonian formulation is given for the gravitational dynamics of two spinning compact bodies to next-to-leading order ($G/c^4$ and $G^2/c^4$) in the spin-orbit interaction. We use a novel approach (valid to linear order in the spins) which starts from the second-post-Newtonian metric (in Arnowitt-Deser-Misner coordinates) generated by two spinless bodies and computes the next-to-leading order precession, in this metric, of suitably redefined “constant-magnitude” 3-dimensional spin vectors ${\mathbf{S}}_1$, ${\mathbf{S}}_2$. We prove the Poincaré invariance of our Hamiltonian by explicitly constructing 10 phase-space generators realizing the Poincaré algebra. A remarkable feature of our approach is that it allows one to derive the orbital equations of motion of spinning binaries to next-to-leading order in spin-orbit coupling without having to solve Einstein’s field equations with a spin-dependent stress tensor. We show that our Hamiltonian (orbital and spin) dynamics is equivalent to the dynamics recently obtained by Faye, Blanchet, and Buonanno, by solving Einstein’s equations in harmonic coordinates.

We investigate properties of a quasilocal mass in a higher-dimensional spacetime having symmetries corresponding to the isomertries of an ($n-2$)-dimensional maximally symmetric space in Einstein-Gauss-Bonnet gravity in the presence of a cosmological constant. We assume that the Gauss-Bonnet coupling constant is non-negative. The quasilocal mass was recently defined by one of the authors as a counterpart of the Misner-Sharp quasilocal mass in general relativity. The quasilocal mass is found to be a quasilocal conserved charge associated with a locally conserved current constructed from the generalized Kodama vector and exhibits the unified first law corresponding to the energy-balance law. In the asymptotically flat case, it converges to the Arnowitt-Deser-Misner mass at spacelike infinity, while it converges to the Deser-Tekin and Padilla mass at infinity in the case of asymptotically anti-de Sitter. Under the dominant energy condition, we show the monotonicity of the quasilocal mass for any $k$, while the positivity on an untrapped hypersurface with a regular center is shown for $k=1$ and for $k=0$ with an additional condition, where $k=\pm 1$, 0 is the constant sectional curvature of each spatial section of equipotential surfaces. Under a special relation between coupling constants, positivity of the quasilocal mass is shown for any $k$ without assumptions above. We also classify all the vacuum solutions by utilizing the generalized Kodama vector. Lastly, several conjectures on further generalization of the quasilocal mass in Lovelock gravity are proposed.

We discuss the entropy-area relation for the small black holes with higher curvature corrections by using the entropy function formalism and field redefinition method. We show that the entropy $S_{BH}$ of the small black hole is proportional to its horizon area $A$. In particular, we find a universal result that $S_{BH}=A/2G$, the ratio is 2 times of Bekenstein-Hawking entropy-area formula in many cases of physical interest. In four dimensions, the universal relation is always true irrespective of the coefficients of the higher-order terms if the dilaton couplings are the same, which is the case for string effective theory, while in five dimensions, the relation again holds irrespective of the overall coefficient if the higher-order corrections are in the GB combination. We also discuss how this result generalizes to known physically interesting cases with Lovelock correction terms in various dimensions, and possible implications of the universal relation.

We show how to differentiate the minimal supersymmetric extension of the standard model from black hole events at the CERN Large Hadron Collider. Black holes are simulated with the CATFISH generator. Supersymmetry simulations use a combination of pythia and isajet. Our study, based on event-shape variables, visible and missing momenta, and analysis of dilepton events, demonstrates that supersymmetry and black hole events at the LHC can be easily discriminated.

A massless spin-2 field equation in de Sitter space, which is invariant under the conformal transformation, has been obtained. The framework utilized is the symmetric rank-2 tensor field of the conformal group. Our method is based on the group theoretical approach and six-cone formalism, initially introduced by Dirac. Dirac’s six-cone is used to obtain conformally invariant equations on de Sitter space. The solution of the physical sector of massless spin-2 field (linear gravity) in de Sitter ambient space is written as a product of a generalized polarization tensor and a massless minimally coupled scalar field. Similar to the minimally coupled scalar field, for quantization of this sector, the Krein space quantization is utilized. We have calculated the physical part of the linear graviton two-point function. This two-point function is de Sitter invariant and free of pathological large-distance behavior.

We study the process whereby quantum cosmological perturbations become classical within inflationary cosmology. By setting up a master-equation formulation we show how quantum coherence for super-Hubble modes can be destroyed by its coupling to the environment provided by sub-Hubble modes. We identify what features the sub-Hubble environment must have in order to decohere the longer wavelengths, and identify how the onset of decoherence (and how long it takes) depends on the properties of the sub-Hubble physics which forms the environment. Our results show that the decoherence process is largely insensitive to the details of the coupling between the sub- and super-Hubble scales. They also show how locality implies, quite generally, that the decohered density matrix at late times is diagonal in the field representation (as is implicitly assumed by extant calculations of inflationary density perturbations). Our calculations also imply that decoherence can arise even for couplings which are as weak as gravitational in strength.

We analyze the non-Gaussian density perturbations generated in ekpyrotic/cyclic models based on heterotic M theory. In this picture, two scalar fields produce nearly scale-invariant entropic perturbations during an ekpyrotic phase that are converted into curvature modes after the ekpyrotic phase is complete and just before the big bang. Both intrinsic nonlinearity in the entropy perturbation and the conversion process contribute to non-Gaussianity. The range of the non-Gaussianity parameter $f_{\mathrm{NL}}$ depends on how gradual the conversion process is and the steepness of the scalar field potential during the ekpyrotic phase. Although a wider range is possible, in principle, natural values of the ekpyrotic parameters combined with a gradual conversion process lead to values of $-50\lesssim f_{\mathrm{NL}}\lesssim +200$, typically much greater than slow-roll inflation but within the current observational bounds.

A linear relation between Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing parameters, $\overline{\eta }=\tan {\Phi }_{3/2}(\overline{\rho }-0.24\pm 0.03)$, involving a $1\sigma$ range for ${\Phi }_{3/2}$, $20°<{\Phi }_{3/2}<115°$, is obtained from $B^0\to K^{*}\pi$ amplitudes measured recently in Dalitz plot analyses of $B^0\to K^{+}{\pi }^{-}{\pi }^0$ and $B^0(t)\to K_S{\pi }^{+}{\pi }^{-}$. This relation is consistent within the large error on ${\Phi }_{3/2}$ with other CKM constraints. We discuss the high sensitivity of this method to a new physics contribution in the $\Delta S=\Delta I=1$ amplitude.

We consider a U(1) gauge theory, minimally coupled to a massless Dirac field, where a higher-derivative term is added to the pure gauge sector, as in the Lee-Wick models. We find that this term can trigger chiral symmetry breaking at low energy in the weak coupling regime. Then, the fermion field acquires a mass that turns out to be a function of both the energy scale associated to the higher-derivative term and the gauge coupling. The dependence of the fermion mass on the gauge coupling is nonperturbative. Extensions to $\mathrm{SU}(N)$ gauge theories and fermion-scalar interactions are also analyzed, as well as to theories with massive gauge fields. A few implications of these results in the framework of quark-mass generation are discussed.

Although taste violations significantly affect the results of staggered calculations of pseudoscalar and heavy-light mesonic quantities, those entering staggered calculations of baryonic quantities have not been quantified. Here I develop staggered chiral perturbation theory in the light-quark baryon sector by mapping the Symanzik action into heavy baryon chiral perturbation theory. For $2+1$ dynamical quark flavors, the masses of flavor-symmetric nucleons are calculated to third order in partially quenched and fully dynamical staggered chiral perturbation theory. To this order the expansion includes the leading chiral logarithms, which come from loops with virtual decuplet-like states, as well as terms of $\mathcal{O}(m_{\pi }^3)$, which come from loops with virtual octet-like states. Taste violations enter through the meson propagators in loops and tree-level terms of $\mathcal{O}(a^2)$. The pattern of taste symmetry breaking and the resulting degeneracies and mixings are discussed in detail. The resulting chiral forms are appropriate to lattice results obtained with operators already in use and could be used to study the restoration of taste symmetry in the continuum limit. I assume that the fourth root of the fermion determinant can be incorporated in staggered chiral perturbation theory using the replica method.

The folklore tradition about the QCD phase diagram is that at the chiral restoration phase transition at finite density hadrons are deconfined and there appears the quark matter. We address this question within the only known exactly solvable confining and chirally symmetric model. It is postulated within this model that there exists linear Coulomb-like confining interaction. The chiral symmetry breaking and the quark Green function are obtained from the Schwinger-Dyson (gap) equation while the color-singlet meson spectrum results from the Bethe-Salpeter equation. We solve this model at $T=0$ and finite chemical potential $\mu$ and obtain a clear chiral restoration phase transition at the critical value ${\mu }_{cr}$. Below this value the spectrum is similar to the previously obtained one at $\mu =0$. At $\mu >{\mu }_{cr}$ the quarks are still confined and the physical spectrum consists of bound states which are arranged into a complete set of exact chiral multiplets. This explicitly demonstrates that a chirally symmetric matter consisting of confined but chirally symmetric hadrons at finite chemical potential is also possible in QCD. If so, there must be nontrivial implications for astrophysics.

Much work has been devoted to the study of nonstrange baryons belonging to the $[\mathbf{70},1^{-}]$ multiplet in the framework of the $1/N_c$ expansion. Using group theoretical arguments here we examine the relation between the exact wave function and the approximate one, customarily used in applications where the system is separated into a ground state core and an excited quark. We show that the exact and approximate wave functions globally give similar results for all of the mass operators presented in this work. However, we find that the inclusion of operators acting separately on the core and on the excited quark deteriorates the fit and leads to unsatisfactory values for the coefficients which encode the quark dynamics. Much better results are obtained when we include operators acting on the whole system, both for the exact and the approximate wave function.

QCD string model is employed to calculate the masses and spin splittings of lowest charmonium hybrid states with a magnetic gluon. Relative decay rates into various $S$- and $P$-wave $D$-meson pairs are calculated for these hybrids.

Quantum decoherence, the evolution of pure states into mixed states, may be a feature of quantum-gravity models. In most cases, such models lead to fewer neutrinos of all active flavors being detected in a long-baseline experiment as compared to three-flavor standard neutrino oscillations. We discuss the potential of the CNGS and J-PARC beams in constraining models of quantum-gravity induced decoherence using neutrino oscillations as a probe. We use as much as possible model-independent parametrizations, even though they are motivated by specific microscopic models, for fits to the expected experimental data which yield bounds on quantum-gravity decoherence parameters.