Low-energy scattering of $D^{*+}$ and ${\overline{D}}_1^0$ meson are studied using quenched lattice QCD with improved lattice actions on anisotropic lattices. The calculation is performed within Lüscher’s finite-size formalism, which establishes the relation between the scattering phase in the infinite volume and the exact energy level in the finite volume. The threshold scattering parameters, namely, the scattering length $a_0$ and the effective range $r_0$, for the $s$-wave scattering in $J^P=0^{-}$ channel are extracted. After the chiral and continuum extrapolations, we obtain: $a_0=2.52(47)\mathrm{fm}$ and $r_0=0.7(1)\mathrm{fm}$ where the errors are purely statistical. Based on these results, we discuss the possibility of a shallow bound state for the two charmed mesons within the nonrelativistic potential scattering model. It is argued that, albeit the interaction between the two charmed mesons being attractive, it is unlikely that they can form a shallow bound state in this channel. This calculation provides some useful information on the nature of the newly discovered resonancelike structure $Z^{+}(4430)$ by the Belle Collaboration.

We derive the topological susceptibility to the one-loop order in the chiral effective theory of QCD, for an arbitrary number of flavors.

We propose stable exotic nuclei bound with $\overline{D}$ and $B$ mesons with respect to heavy quark symmetry. We indicate that an approximate degeneracy of $\overline{D}(B)$ and ${\overline{D}}^{*}(B^{*})$ mesons plays an important role, and discuss the stability of $\overline{D}N$ and $BN$ bound states. We find the binding energies 1.4 MeV and 9.4 MeV for each state in the $J^P=1/2^{-}$ with the $I=0$ channel. We discuss also possible existence of exotic nuclei $\overline{D}NN$ and $BNN$.

We propose a chiral random matrix model which properly incorporates the flavor-number dependence of the phase transition owing to the ${\mathrm{U}}_{\mathrm{A}}(1)$ anomaly term. At finite temperature, the model shows the second-order phase transition with mean-field critical exponents for two massless flavors, while in the case of three massless flavors the transition turns out to be of the first order. The topological susceptibility satisfies the anomalous ${\mathrm{U}}_{\mathrm{A}}(1)$ Ward identity and decreases gradually with the temperature increased.

We study the low energy phenomena induced by the lightest charged Higgs in the private Higgs model, in which each quark flavor is associated with a Higgs doublet. We show that the couplings of the charged Higgs scalars to fermions are fixed and the unknown parameters are only the masses and mixing elements of the charged Higgs scalars. As the charged Higgs masses satisfy with $M_b<M_c\ll M_s\ll M_{d,u}$, processes involving $B$-meson are expected to be the ideal places to test the private Higgs model. In particular, we explore the constraints on the model from experimental data in $B$ physics, such as the branching ratio (BR) and $CP$ asymmetry of $B\to X_s\gamma$, $B_{d,s}\mathrm{\text{−}}{\overline{B}}_{d,s}$ mixings and the BR for $B\to K^{*}{\ell }^{+}{\ell }^{-}$. We illustrate that the sign of the Wilson coefficient for $B\to X_s\gamma$ can be different from that in the standard model, while this flipped sign can be displayed by the forward-backward asymmetry of $B\to V{\ell }^{+}{\ell }^{-}$ with $V$ a vector meson. We also demonstrate that $B_{d,s}\mathrm{\text{−}}{\overline{B}}_{d,s}$ mixings and their time-dependent $CP$ asymmetries are negligible small and the BR of $B\to K^{*}{\ell }^{+}{\ell }^{-}$ can have a more strict bound than that of $B\to X_s\gamma$.

The model (Lagrangian) with a peculiar extra $U(1)$ [S. M. Barr and I. Dorsner, Phys. Rev. D 72, 015011 (2005); S. M. Barr and A. Khan, Phys. Rev. D 74, 085023 (2006)] is clearly presented. The assigned extra $U(1)$ gauge charges give a strong constraint to build Lagrangians. The $Z^{\prime }$ discovery limits are estimated and predicted at the Tevatron and the LHC. The new contributions of the muon anomalous magnetic moment are investigated at one and two loops, and we predict that the deviation from the standard model may be explained. The electron electric dipole moment could also be generated because of the explicit $CP$-violation effect in the Higgs sector, and a sizable contribution is expected for a moderately sized $CP$ phase [argument of the $CP$-odd Higgs], $0.1\le \sin \delta \le 1$ [$6°\le \arg (A)\le 90°$].

In the context of a warped extra dimension with standard model fields in the bulk, we obtain the general flavor structure of the radion couplings to fermions and show that the result is independent of the particular nature of the Higgs mechanism (bulk or brane localized). These couplings will be generically misaligned with respect to the fermion mass matrix when the fermion bulk mass parameters are not all degenerate. When the radion is light enough, the generic size of these tree-level flavor changing couplings will be strongly constrained by the experimental bounds on $\Delta F=2$ processes. At the LHC the possibility of a heavier radion decaying into top and charm quarks is then considered as a promising signal to probe the flavor structure of both the radion sector and the whole scenario.

We have measured the differential cross section for the inclusive production of $\psi (2\mathrm{S})$ mesons decaying to ${\mu }^{+}{\mu }^{-}$ that were produced in prompt or $B$-decay processes from $p\overline{p}$ collisions at 1.96 TeV. These measurements have been made using a data set from an integrated luminosity of $1.1{\mathrm{fb}}^{-1}$ collected by the CDF II detector at Fermilab. For events with transverse momentum $p_T(\psi (2\mathrm{S}))>2\mathrm{GeV}/c$ and rapidity $|y(\psi (2\mathrm{S}))|<0.6$ we measure the integrated inclusive cross section $\sigma (p\overline{p}\to \psi (2\mathrm{S})X)·\mathrm{Br}(\psi (2\mathrm{S})\to {\mu }^{+}{\mu }^{-})$ to be $3.29\pm 0.04(\mathrm{stat})\pm 0.32(\mathrm{syst})\mathrm{nb}$.

By applying the known expressions for super Yang-Mills (SYM) and supergravity (SUGRA) tree amplitudes, we write generating functions for the next-to-next-to-maximally helicity violating (NNMHV) box coefficients of SYM as well as the maximally helicity violating, next-to-maximally helicity violating, and NNMHV box coefficients for SUGRA. The all-multiplicity generating functions utilize covariant, on-shell superspace whereby the contribution from arbitrary external states in the supermultiplet can be extracted by Grassmann operators. In support of the relation between dual-Wilson loops and SYM scattering amplitudes at weak coupling, the SYM amplitudes are presented in a manifestly dual superconformal form. We introduce ordered box coefficients for calculating SUGRA quadruple cuts and prove that ordered coefficients generate physical cut amplitudes after summing over permutations of the external legs. The ordered box coefficients are produced by sewing ordered subamplitudes, previously used in applying on-shell recursion relations at tree level. We describe our verification of the results against the literature, and a formula for extracting the contributions from external gluons or gravitons to NNMHV superamplitudes is presented.

If the color Coulomb potential is confining, then the Coulomb field energy of an isolated color charge is infinite on an infinite lattice, even if the usual UV divergence is lattice regulated. A simple criterion for Coulomb confinement is that the expectation value of timelike link variables vanishes in the Coulomb gauge, but it is unclear how this criterion is related to the spectrum of the corresponding Faddeev-Popov operator, which can be used to formulate a quite different criterion for Coulomb confinement. The purpose of this article is to connect the two seemingly different Coulomb confinement criteria, and explain the geometrical basis of the connection.

After a brief review of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach to Regge processes in QCD and in supersymmetric gauge theories we propose a strategy for calculating the next-to-next-to-leading order corrections to the BFKL kernel. They can be obtained in terms of various cross sections for Reggeized gluon interactions. The corresponding amplitudes can be calculated in the framework of the effective action for high-energy scattering. In the case of $N=4$ supersymmetry it is also possible to use the Bern-Dixon-Smirnov ansatz. For this purpose the analytic properties of the Bern-Dixon-Smirnov amplitudes at high energies are investigated, in order to verify their self-consistency. It is found that, for the number of external particles being larger than 5, these amplitudes, beyond one loop, are not in agreement with the BFKL approach which predicts the existence of Regge cuts in some physical channels.

We perform a complete analytical reduction of general one-loop Feynman integrals with five and six external legs for tensors up to rank $R=3$ and 4, respectively. An elegant formalism with extensive use of signed minors is developed for the cancellation of inverse Gram determinants. The 6-point tensor functions of rank $R$ are expressed in terms of 5-point tensor functions of rank $R-1$, and the latter are reduced to scalar four-, three-, and two-point functions. The resulting compact formulas allow both for a study of analytical properties and for efficient numerical programming. They are implemented in Fortran and Mathematica.

We perform a numerical study of the systematic effects involved in the determination of the critical line at real baryonic chemical potential by analytic continuation from results obtained at imaginary chemical potentials. We present results obtained in theories free of the sign problem, such as two-color QCD with finite baryonic density and three-color QCD with finite isospin chemical potential, and comment on general features which could be relevant also to the continuation of the critical line in real QCD at finite baryonic density.

The $D^{*}{\overline{D}}^{*}$ and $B^{*}{\overline{B}}^{*}$ systems are studied dynamically in the one boson exchange model, where $\pi$, $\eta$, $\sigma$, $\rho$ and $\omega$ exchanges are taken into account. Ten allowed states with low spin parity are considered. We suggest that the $1^{--}$, $2^{++}$, $0^{++}$ and $0^{-+}$ $B^{*}{\overline{B}}^{*}$ molecules should exist, and the $D^{*}{\overline{D}}^{*}$ bound states with the same quantum numbers very likely exist as well. However, the $CP$ exotic $(1^{-+},2^{+-})$ $B^{*}{\overline{B}}^{*}$ and $D^{*}{\overline{D}}^{*}$ states may not be bound by the one boson exchange potential. We find that the $I=0$ configuration is more deeply bound than the $I=1$ configuration, hence $Z_1^{+}(4050)$ may not be a $D^{*}{\overline{D}}^{*}$ molecule. Although $Y(4008)$ is close to the $D^{*}{\overline{D}}^{*}$ threshold, the interpretation of $Y(4008)$ as a $D^{*}{\overline{D}}^{*}$ molecule is not favored by its huge width. $1^{--}$ $D^{*}{\overline{D}}^{*}$ and $B^{*}{\overline{B}}^{*}$ states can be produced copiously in $e^{+}{e}^{-}$ annihilation, detailed scanning of the $e^{+}{e}^{-}$ annihilation data near the $D^{*}{\overline{D}}^{*}$ and $B^{*}{\overline{B}}^{*}$ threshold is an important check to our predictions.

We study the role of magnetic monopoles at high enough temperature $T>2T_c$, when they can be considered heavy, rare objects embedded into matter consisting mostly of the usual “electric” quasiparticles, quarks, and gluons. We review available lattice results on monopoles at finite temperatures. Then we proceed to classical and quantum charge-monopole scattering, solving the problem of gluon-monopole scattering for the first time. The explicit calculations are performed in the framework of the Georgi-Glashow model; the results that we obtain are nevertheless quite general. Connections to QCD are carefully discussed. We find that, while the gluon-monopole scattering hardly influences thermodynamic quantities, it does produce a large transport cross section, significantly exceeding that for pQCD gluon-gluon scattering up to quite high $T$. Thus, in spite of their relatively small density at high $T$, monopoles are extremely important for quark-gluon plasma transport properties, keeping viscosity small enough for hydrodynamics to work at the LHC.

We present a study of the decays $B^0\to D^0{K}^{*0}$ and $B^0\to {\overline{D}}^0{K}^{*0}$ with $K^{*0}\to K^{+}{\pi }^{-}$. The $D^0$ and the ${\overline{D}}^0$ mesons are reconstructed in the final states $f=K^{+}{\pi }^{-}$, $K^{+}{\pi }^{-}{\pi }^0$, $K^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$, and their charge conjugates. Using a sample of $465\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider at SLAC, we measure the ratio $R_{\mathrm{ADS}}\equiv [\Gamma ({\overline{B}}^0\to [f{]}_D{\overline{K}}^{*0})+\Gamma (B^0\to [\overline{f}{]}_D{K}^{*0})]/[\Gamma ({\overline{B}}^0\to [\overline{f}{]}_D{\overline{K}}^{*0})+\Gamma (B^0\to [f{]}_D{K}^{*0})]$ for the three final states. We do not find significant evidence for a signal and set the following limits at 95% probability: $R_{\mathrm{ADS}}(K\pi )<0.244$, $R_{\mathrm{ADS}}(K\pi {\pi }^0)<0.181$, and $R_{\mathrm{ADS}}(K\pi \pi \pi )<0.391$. From the combination of these three results, we find that the ratio $r_S$ between the $b\to u$ and the $b\to c$ amplitudes lies in the range [0.07,0.41] at 95% probability.

We study the entanglement of closed strings degrees of freedom in order to investigate the microscopic structure and statistics of objects as D-branes. By considering the macroscopic pure state limit, whenever the entanglement entropy goes to zero (in such a way that the macroscopic properties of the state are preserved), we show that boundary states may be recovered in this limit and, furthermore, the description through closed string (perturbative) degrees of freedom collapses. We also show how the thermal properties of branes and closed strings could be described by this model, and it requires that dissipative effects be taken into account. Extensions of the macroscopic pure state analysis to more general systems at finite temperature are finally emphasized.

We consider semidirect gauge mediation models of supersymmetry breaking where the messengers are composite fields and their supersymmetric mass is naturally generated through quartic superpotential couplings. We show that such composite messenger models can be easily embedded in quiver gauge theories arising from D-branes at Calabi-Yau singularities, and argue that semidirect gauge mediation is in fact a very natural option for supersymmetry breaking in D-brane models. We provide several explicit examples and discuss their salient phenomenological properties.

Observations of gravitational waves from massive binary black-hole systems at cosmological distances can be used to search for a dependence of the speed of propagation of the waves on wavelength, and thereby to bound the mass of a hypothetical graviton. We study the effects of precessions of the spins of the black holes and of the orbital angular momentum on the process of parameter estimation based on the method of matched filtering of gravitational-wave signals vs theoretical template waveforms. For the proposed Laser Interferometer Space Antenna, we show that precessions, and the accompanying modulations of the gravitational waveforms, are effective in breaking degeneracies among the parameters being estimated, and effectively restore the achievable graviton-mass bounds to levels obtainable from binary inspirals without spin. For spinning, precessing binary black-hole systems of equal masses ${10}^6{M}_{\odot }$ at 3 Gpc, the lower bounds on the graviton Compton wavelength achievable are of the order of $5\times {10}^{16}\mathrm{km}$.

The generalization of QCD to many colors is not unique; each distinct choice corresponds to a distinct $1/N_c$ expansion. The familiar ’t Hooft $N_c\to \infty$ limit places quarks in the fundamental representation of $\mathrm{SU}(N_c)$, while an alternative approach places quarks in its two-index antisymmetric representation. At $N_c=3$ these two $1/N_c$ expansions coincide. We compare their predictions for certain observables in baryon spectroscopy, particularly mass combinations organized according to SU(3) flavor breaking. Each large $N_c$ limit generates an emergent spin-flavor symmetry that leads to the vanishing of particular linear combinations of baryon masses at specific orders in the expansions. Experimental evidence shows that these relations hold at the expected orders regardless of which large $N_c$ limit one uses, suggesting the validity of either limit in the study of baryons. We also consider a hybrid large $N_c$ limit in which one flavor is taken to transform in the two-index antisymmetric representation and the rest of the flavors are in the fundamental representation. While this hybrid large $N_c$ limit is theoretically attractive, we show that for a wide class of observables it faces some phenomenological difficulties.