Several exclusive $B_s^0$ decays are studied using a $1.86{\mathrm{fb}}^{-1}$ data sample collected at the ${\rm Y}(5S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^{+}{e}^{-}$ collider. In the $B_s^0\to D_s^{-}{\pi }^{+}$ decay mode we find 10 $B_s^0$ candidates and measure the corresponding branching fraction. Combining the $B_s^0\to D_s^{(*)-}{\pi }^{+}$, $B_s^0\to D_s^{(*)-}{\rho }^{+}$, $B_s^0\to J/\psi \varphi$, and $B_s^0\to J/\psi \eta$ decay modes, a significant $B_s^0$ signal is observed. The ratio $\sigma (e^{+}{e}^{-}\to B_s^{*}{\overline{B}}_s^{*})/\sigma (e^{+}{e}^{-}\to B_s^{(*)}{\overline{B}}_s^{(*)})=({93}_{-9}^{+7}\pm 1)\%$ is obtained at the ${\rm Y}(5S)$ energy, indicating that $B_s^0$ meson production proceeds predominantly through the creation of $B_s^{*}{\overline{B}}_s^{*}$ pairs. The $B_s^0$ and $B_s^{*}$ meson masses are measured to be $M(B_s^0)=(5370\pm 1\pm 3)\mathrm{MeV}/c^2$ and $M(B_s^{*})=(5418\pm 1\pm 3)\mathrm{MeV}/c^2$. Upper limits on the $B_s^0\to \gamma \gamma$, $B_s^0\to \varphi \gamma$, $B_s^0\to K^{+}{K}^{-}$, and $B_s^0\to D_s^{(*)+}{D}_s^{(*)-}$ branching fractions are also reported.

We determine hadronic matrix elements relevant for the mass and width differences, $\Delta M_s$ and $\Delta {\Gamma }_s$, in the $B_s^0-{\overline{B}}_s^0$ meson system using fully unquenched lattice QCD. We employ the MILC Collaboration gauge configurations that include $u$, $d$, and $s$ sea quarks using the improved staggered quark (AsqTad) action and a highly improved gluon action. We implement the valence $s$ quark also with the AsqTad action and use nonrelativistic QCD for the valence $b$ quark. For the nonperturbative QCD input into the standard model expression for $\Delta M_s$ we find $f_{B_s}\sqrt{{\widehat{B}}_{B_s}}=0.281(21)\mathrm{GeV}$. Results for four-fermion operator matrix elements entering standard model formulas for $\Delta {\Gamma }_s$ are also presented.

We study how geometrical and topological aspects of certain $\frac{1}{2}$-BPS type IIB supergravity solutions are captured by the $\mathcal{N}=4$ super Yang-Mills gauge theory in the AdS/CFT context. The type IIB solutions are completely characterized by arbitrary droplets in a plane and we consider, in particular, concentric droplets. We probe the dual $\frac{1}{2}$-BPS operators of the gauge theory with single traces and extract their one-loop anomalous dimensions. The action of the one-loop dilatation operator can be reformulated as the Hamiltonian of a bosonic lattice. The operators defining the Hamiltonian encode the topology of the droplet. The axial symmetry of the droplets turns out to be essential for obtaining the spectrum of the Hamiltonians. In appropriate BMN limits, the near-BPS spectrum reproduces the spectrum of near-BPS string excitations propagating along each individual edge of the droplet of the dual geometric background. We also study semiclassical regimes for the Hamiltonians. We show that, for droplets having disconnected constituents, the Hamiltonian admits different complimentary semiclassical descriptions, each one replicating the semiclassical description for closed strings extending in each of the constituents.

We investigate the analytic structure of the magnon $S$ matrix in the spin-chain description of planar $\mathcal{N}=4$ SUSY Yang-Mills/${\mathrm{AdS}}_5\times S^5$ strings. Semiclassical analysis suggests that the exact $S$ matrix must have a large family of poles near the real axis in momentum space. In this article we show that these are double poles corresponding to the exchange of pairs of Bogomol’nyi-Prasad-Sommerfield (BPS) magnons. Their locations in the complex plane are uniquely fixed by the known dispersion relation for the BPS particles. The locations precisely agree with the recent conjecture for the $S$ matrix by Beisert, Hernandez, Lopez, Eden, and Staudacher (J. High Energy Phys. 11 (2006) 070 and J. Stat. Mech. 01 (2007) P021). These poles do not signal the presence of new bound states. In fact, a certain non-BPS localized classical solution, which was thought to give rise to new bound states, can actually decay into a pair of BPS magnons.

We study that a minimal supersymmetric standard model with an extra $U(1{)}^{\prime }$ gauge symmetry may accommodate the explicit $CP$ violation at the one-loop level through radiative corrections. This model is $CP$ conserving at the tree level and cannot realize the spontaneous $CP$ violation for a wide parameter space at the one-loop level. In explicit $CP$ violation scenario, we calculate the Higgs boson masses and the magnitude of the scalar-pseudoscalar mixings in this model at the one-loop level by taking into account the contributions of top quarks, bottom quarks, exotic quarks, and their superpartners. In particular, we investigate how the exotic quarks and squarks would affect the scalar-pseudoscalar mixings. It is observed that the size of the mixing between the heaviest scalar and pseudoscalar Higgs bosons is changed up to 20% by a complex phase originated from the exotic quark sector of this model.

We present a method for generating new deformed solutions starting from systems of two real scalar fields for which defect solutions and orbits are known. The procedure generalizes the approach introduced in a previous work [Phys. Rev. D 66, 101701(R) (2002)], in which it is shown how to construct new models altogether with its defect solutions, in terms of the original model and solutions. As an illustration, we work out an explicit example in detail.

We derive in a simple way the well-known hard thermal effective action for QCD through the application of the thermal operator to the zero temperature retarded Green’s functions. This derivation also clarifies the origin of important properties of the hard thermal effective action, such as the manifest Lorentz and gauge invariance of its integrand, by relating them directly to the properties of the corresponding zero temperature effective action in the hard regime.

We study the formation of black holes by spherical domain wall collapse as seen by an asymptotic observer, using the functional Schrödinger formalism. To explore what signals such observers will see, we study radiation of a scalar quantum field in the collapsing domain wall background. The total energy flux radiated diverges when backreaction of the radiation on the collapsing wall is ignored, and the domain wall is seen by the asymptotic observer to evaporate by nonthermal “pre-Hawking radiation” during the collapse process. Evaporation by pre-Hawking radiation implies that an asymptotic observer can never lose objects down a black hole. Together with the nonthermal nature of the radiation, this may resolve the black hole information loss problem.

We complete the formulation of a general framework for the analysis of high-order nonspherical perturbations of a four-dimensional spherical spacetime by including a gauge-invariant description of the perturbations. We present a general algorithm to construct these invariants and provide explicit formulas for the case of second-order metric perturbations. We show that the well-known problem of lack of invariance for the first-order perturbations with $l=0$, 1 propagates to increasing values of $l$ for perturbations of higher order, owing to mode coupling. We also discuss in which circumstances it is possible to construct the invariants.

Caustic rings of dark matter were predicted to exist in the plane of the Galaxy at radii $a_n\simeq 40\mathrm{kpc}/n$ for $n=1,2,3,\dots$. The recently discovered Monoceros Ring of stars is located near the $n=2$ caustic, prompting us to consider a possible connection between these two objects. We identify two processes through which the Monoceros Ring of stars may have formed. One process is the migration of gas to an angular velocity minimum at the caustic leading to enhanced star formation there. The other is the adiabatic deformation of star orbits as the caustic slowly grows in mass and radius. The second process predicts an order 100% enhancement of the density of disk stars at the location of the caustic ring.

One interpretation of the unexplained signature observed in the PVLAS experiment invokes a new axionlike particle (ALP) with a two-photon vertex, allowing for photon-ALP oscillations in the presence of magnetic fields. In the range of masses and couplings suggested by PVLAS, the same effect would lead to a peculiar dimming of high-energy photon sources. For typical parameters of the turbulent magnetic field in the galaxy, the effect sets in at $E_{\gamma }\gtrsim 10\mathrm{TeV}$, providing an ALP signature in the spectra of TeV gamma sources that can be probed with Cherenkov telescopes. A dedicated search will be strongly motivated if the ongoing photon regeneration experiments confirm the PVLAS particle interpretation.

Laser interferometer gravitational wave detectors are usually limited by displacement noise in their lower frequency band. Recently, theoretical proposals have been put forward to construct schemes of interferometry that are insusceptible to displacement noise as well as classical laser noise. These so-called displacement-noise-free interferometry (DFI) schemes take advantage of the difference between gravitational waves and displacement noise in their effects on light propagation. However, since this difference diminishes in lower frequencies (i.e., $\Omega <c/{\mathcal{L}}_D$, with ${\mathcal{L}}_D$ the size of the detector), shot-noise-limited sensitivity of DFI schemes deteriorates dramatically in these frequencies—exactly the regime in which they are supposed to be superior, thereby limiting their applicability. In this paper, we explore the obvious possibility of increasing the effective size of the detector in the time domain, by introducing artificial time delays (${\mathcal{T}}_D\gg {\mathcal{L}}_D/c$) into the interferometry scheme, with the hope of improving low-frequency sensitivity. We found that sensitivity can only be improved by schemes in which fluctuations in the artificial time delays are not canceled.

We present a measurement of the $CP$-violating asymmetry in $B^0\to {\rho }^{+}{\rho }^{-}$ decays using $535\times {10}^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. We measure $CP$-violating coefficients $\mathcal{A}=0.16\pm 0.21(\mathrm{stat})\pm 0.08(\mathrm{syst})$ and $\mathcal{S}=0.19\pm 0.30(\mathrm{stat})\pm 0.08(\mathrm{syst})$. These values are used to determine the unitarity triangle angle ${\varphi }_2$ using an isospin analysis; the solution consistent with the standard model lies in the range $54°<{\varphi }_2<113°$ at the 90% confidence level.

A Fokker action for a post-Minkowski approximation with the first post-Newtonian correction is introduced in our previous paper, and a solution for the helically symmetric circular orbit is obtained. We present supplemental results for the circular solution of two unequal mass point particles. Circular solutions for selected mass ratios are found numerically, and analytic formulas in the extreme mass ratio limit are derived. The leading terms of the analytic formulas agree with the first post-Newtonian formulas in this limit.

We study the collision of a brane with a black hole. Our aim is to explore the topology changing process of perforation of a brane. The brane is described as a field theoretical domain wall in the context of an axionlike model consisting of a complex scalar effective field theory with approximate $U(1)$ symmetry. We simulate numerically the dynamics of the collision and illustrate the transition from the configuration without a hole to the pierced one with the aid of a phase diagram. The process of perforation is found to depend on the collisional velocity, and, contrary to our expectation, we observe that above a critical value of the velocity, the black hole has no chance to perforate the wall. That is: high energy collisions do not assist piercing. We also show that, only when the model parameters are fine-tuned so that the energy scale of the string is very close to that of the domain wall, the collision of the wall with the black hole has a possibility to provide a mechanism to erase domain walls, if the hole expands. However, in such cases, domain walls will form with many holes edged by a string and therefore disappear eventually. Therefore this mechanism is unlikely to be a solution to the cosmological domain wall problem, although it may cause some minor effects on the evolution of a domain wall network.

We consider the extent to which future imaging surveys of galaxies can distinguish between dark energy and modified gravity models for the origin of the cosmic acceleration. Dynamical dark energy models may have similar expansion rates as models of modified gravity, yet predict different growth of structure histories. We parametrize the cosmic expansion by the two parameters, $w_0$ and $w_a$, and the linear growth rate of density fluctuations by Linder’s $\gamma$, independently. Dark energy models generically predict $\gamma \approx 0.55$, while the Dvali-Gabadadze-Porrati (DGP) model $\gamma \approx 0.68$. To determine if future imaging surveys can constrain $\gamma$ within 20% (or $\Delta \gamma <0.1$), we perform the Fisher matrix analysis for a weak-lensing survey such as the ongoing Hyper Suprime-Cam (HSC) project. Under the condition that the total observation time is fixed, we compute the figure of merit (FoM) as a function of the exposure time $t_{\exp }$. We find that the tomography technique effectively improves the FoM, which has a broad peak around $t_{\exp }\simeq \mathrm{\text{several}}\sim 10\min$; a shallow and wide survey is preferred to constrain the $\gamma$ parameter. While $\Delta \gamma <0.1$ cannot be achieved by the HSC weak-lensing survey alone, one can improve the constraints by combining with a follow-up spectroscopic survey like Wide-field Fiber-fed Multi-Object Spectrograph (WFMOS) and/or future cosmic microwave background (CMB) observations.

We revisit the problem of constraining steps in the inflationary potential with cosmological data. We argue that a step in the inflationary potential produces qualitatively similar oscillations in the primordial power spectrum, independently of the details of the inflationary model. We propose a phenomenological description of these oscillations and constrain these features using a selection of cosmological data including the baryonic peak data from the correlation function of luminous red galaxies in the Sloan Digital Sky Survey. Our results show that degeneracies of the oscillation with standard cosmological parameters are virtually nonexistent. The inclusion of new data severely tightens the constraints on the parameter space of oscillation parameters with respect to older work. This confirms that extensions to the simplest inflationary models can be successfully constrained using cosmological data.

Data from the LIGO Livingston interferometer and the ALLEGRO resonant-bar detector, taken during LIGO’s fourth science run, were examined for cross correlations indicative of a stochastic gravitational-wave background in the frequency range 850–950 Hz, with most of the sensitivity arising between 905 and 925 Hz. ALLEGRO was operated in three different orientations during the experiment to modulate the relative sign of gravitational-wave and environmental correlations. No statistically significant correlations were seen in any of the orientations, and the results were used to set a Bayesian 90% confidence level upper limit of ${\Omega }_{\mathrm{gw}}(f)\le 1.02$, which corresponds to a gravitational-wave strain at 915 Hz of $1.5\times {10}^{-23}{\mathrm{Hz}}^{-1/2}$. In the traditional units of $h_{100}^2{\Omega }_{\mathrm{gw}}(f)$, this is a limit of 0.53, 2 orders of magnitude better than the previous direct limit at these frequencies. The method was also validated with successful extraction of simulated signals injected in hardware and software.

We generalize the relativistic flux tube model for arbitrary two- or three-body systems. The spin-independent and spin-dependent contributions of the flux tube to the total Hamiltonian are computed in perturbation theory. In particular, we show that the spin-dependent part exhibits a universal spin-orbit form: It does not depend on the nature of the confined particles. The general equations we present, being well defined for light particles, can thus be applied to usual as well as exotic hadrons such as hybrid mesons and glueballs.