Increasing the sensitivity of a gravitational-wave (GW) detector improves our ability to measure the characteristics of detected sources. It also increases the number of weak signals that contribute to the data. Because GW detectors have nearly all-sky sensitivity, they can be subject to a confusion limit: Many sources which cannot be distinguished may be measured simultaneously, defining a stochastic noise floor to the sensitivity. For GW detectors operating at present and for their planned upgrades, the projected event rate is sufficiently low that we are far from the confusion-limited regime. However, some detectors currently under discussion may have large enough reach to binary inspiral that they enter the confusion-limited regime. In this paper, we examine the binary inspiral confusion limit for terrestrial detectors. We consider a broad range of inspiral rates in the literature, several planned advanced gravitational-wave detectors, and the highly advanced “Einstein telescope” design. Though most advanced detectors will not be impacted by this limit, the Einstein telescope with a very low-frequency “seismic wall” may be subject to confusion noise. At a minimum, careful data analysis will be require to separate signals which will appear confused. This result should be borne in mind when designing highly advanced future instruments.

We consider a four site Higgsless model based on the $SU(2{)}_L\times SU(2{)}_1\times SU(2{)}_2\times U(1{)}_Y$ gauge symmetry, which predicts two neutral and four charged extra gauge bosons, $Z_{1,2}$ and $W_{1,2}^{\pm }$. We compute the properties of the new particles, and derive indirect and direct limits on their masses and couplings from the CERN LEP and Tevatron data. In contrast to other Higgsless models, characterized by fermiophobic extra gauge bosons, here sizeable fermion-boson couplings are allowed by the electroweak precision data. The prospects of detecting the new predicted particles in the favored Drell-Yan channel at the CERN LHC are thus investigated. The outcome is that all six extra gauge bosons could be discovered in the early stage of the LHC low-luminosity run.

Exclusive ${\pi }^o$ electroproduction from nucleons is suggested for extracting the tensor charge and other quantities related to transversity from experimental data. This process isolates C-parity odd and chiral-odd combinations of t-channel exchange quantum numbers. In a hadronic picture it connects the meson production amplitudes to C-odd Regge exchanges with final state interactions. In a description based on partonic degrees of freedom, the helicity structure for this C-odd process relates to the quark helicity flip, or chiral-odd generalized parton distributions. This differs markedly from deeply virtual Compton scattering, and both vector meson and charged $\pi$ electroproduction, where the axial charge can enter the amplitudes. Contrarily, the tensor charge enters the ${\pi }^o$ process. The connection through the helicity description of the process to both the partonic and hadronic perspectives is studied and exploited in model calculations to indicate how the tensor charge and other transversity parameters can be related to cross section and spin asymmetry measurements over a broad range of kinematics.

We present a study of the charmless semileptonic $B$-meson decays $B^{+}\to \omega {\ell }^{+}\nu$ and $B^{+}\to \eta {\ell }^{+}\nu$. The analysis is based on $3.83\times {10}^8$ $B\overline{B}$ pairs recorded at the ${\rm Y}(4S)$ resonance with the BABAR detector. The $\omega$ mesons are reconstructed in the channel $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$ and the $\eta$ mesons in the channels $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$ and $\eta \to \gamma \gamma$. We measure the branching fractions $\mathcal{B}(B^{+}\to \omega {\ell }^{+}\nu )=(1.14\pm {0.16}_{\mathrm{stat}}\pm {0.08}_{\mathrm{syst}})\times {10}^{-4}$ and $\mathcal{B}(B^{+}\to \eta {\ell }^{+}\nu )=(0.31\pm {0.06}_{\mathrm{stat}}\pm {0.08}_{\mathrm{syst}})\times {10}^{-4}$.

Using $\psi (3770)\to D\overline{D}$ events collected with the CLEO-c detector at the Cornell $e^{+}{e}^{-}$ storage ring, tagged by fully reconstructing one $D$ meson in a hadronic decay mode, we measure absolute branching fractions and differential decay rates for $D^0\to {\pi }^{-}{e}^{+}{\nu }_e$, $D^{+}\to {\pi }^0{e}^{+}{\nu }_e$, $D^0\to K^{-}{e}^{+}{\nu }_e$, and $D^{+}\to {\overline{K}}^0{e}^{+}{\nu }_e$. The measured decay rates are used to study semileptonic form factors governing these transitions and to test unquenched Lattice QCD (LQCD) calculations. We average our results with previously published CLEO-c measurements of the same quantities using a neutrino reconstruction technique. Combining LQCD calculations of form factor absolute normalizations $f_{+}(0)$ and measurements of $f_{+}^{\pi }(0)|V_{cd}|$ and $f_{+}^K(0)|V_{cs}|$, we find $|V_{cd}|=0.222(8)(3)(23)$ and $|V_{cs}|=1.018(10)(8)(106)$, where the uncertainties are statistical, experimental systematic, and from LQCD, respectively.

The differential cross sections for the process $\gamma \gamma \to {\pi }^0{\pi }^0$ have been measured in the kinematic range $0.6\mathrm{GeV}<W<4.1\mathrm{GeV}$, $|\cos {\theta }^{*}|<0.8$ in energy and pion scattering angle, respectively, in the $\gamma \gamma$ center-of-mass system. The results are based on a $223{\mathrm{fb}}^{-1}$ data sample collected with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. The differential cross sections are fitted in the energy region $1.7\mathrm{GeV}<W<2.5\mathrm{GeV}$ to confirm the two-photon production of two pions in the $G$ wave. In the higher-energy region, we observe production of the ${\chi }_{c0}$ charmonium state and obtain the product of its two-photon decay width and branching fraction to ${\pi }^0{\pi }^0$. We also compare the observed angular dependence and ratios of cross sections for neutral-pion and charged-pion pair production to QCD models. The energy and angular dependence above 3.1 GeV are compatible with those measured in the ${\pi }^{+}{\pi }^{-}$ channel, and in addition we find that the cross section ratio, $\sigma ({\pi }^0{\pi }^0)/\sigma ({\pi }^{+}{\pi }^{-})$, is $0.32\pm 0.03\pm 0.05$ on average in the 3.1–4.1 GeV region.

We find an explicit cosmological model which allows a special type of cosmological singularity which we call a $w$-singularity. This singularity has the scale factor finite, the energy density and pressure vanishing, and the only singular behavior appears in a time-dependent barotropic index $w(t)$. It is different from the type IV cosmological singularity in that it does not exhibit the divergence of the higher derivatives of the Hubble parameter and from the big brake since it does not fulfill the anti-Chaplygin gas equation of state. We also find an interesting duality between the $w$-singularities and the big-bang singularities. Physical examples of $w$-singularities appear in $f(R)$, scalar field and brane cosmologies.

Atomic clock comparisons provide some of the most precise tests of Lorentz and CPT symmetries in the laboratory. With data from multiple such experiments using different nuclei, it is possible to constrain new regions of the parameter space for Lorentz violation. Relativistic effects in the nuclei allow us to disentangle forms of Lorentz violation which could not be separately measured in purely nonrelativistic experiments. The disentangled bounds in the neutron sectors are at the ${10}^{-28}\mathrm{GeV}$ level, far better than could be obtained with any other current technique.

We continue our previous study on what are the allowed forms of quark mass matrices in the Randall-Sundrum framework that can reproduce the experimentally observed quark mass spectrum and the pattern of Cabibbo-Kobayashi-Maskawa mixing. We study the constraints the $\Delta F=2$ processes in the neutral meson sector placed on the admissible forms found there, and we found only the asymmetrical type of quark mass matrices arising from anarchical Yukawa structures remain viable at the few TeV scale reachable at the LHC. We study also the decay of the first Kaluza-Klein (KK) excitation of the gluon. We give the decay branching ratios of the first KK gluon into quark pairs, and we point out that measurements of the decay width and just one of the quark spins in the dominant $\overline{t}t$ decays can be used to extract the effective coupling of the first KK gluon to top quarks for both chiralities. This provides a further probe into the flavor structure of the Randall-Sundrum framework.

In this paper we present a study of the interaction of a low energy electron antineutrino on nuclei that undergo electron capture. We show that the two corresponding crossed reactions have a sizable cross section and are both suitable for detection of low energy antineutrino. However, only in the case where very specific conditions on the $Q$ value of the decay are met or significant improvements on the performances of ion storage rings are achieved, these reactions could be exploited in the future to address the long standing problem of a direct detection of cosmological neutrino background.

A measurement of the $b$ jet production cross section is presented for events containing a $Z$ boson produced in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$, using data corresponding to an integrated luminosity of $2{\mathrm{fb}}^{-1}$ collected by the CDF II detector at the Tevatron. $Z$ bosons are selected in the electron and muon decay modes. Jets are considered with transverse energy $E_T>20\mathrm{GeV}$ and pseudorapidity $|\eta |<1.5$ and are identified as $b$ jets using a secondary vertex algorithm. The ratio of the integrated $Z+b$ jet cross section to the inclusive $Z$ production cross section is measured to be $3.32\pm 0.53(\mathrm{stat})\pm 0.42(\mathrm{syst})\times {10}^{-3}$. This ratio is also measured differentially in jet $E_T$, jet $\eta$, $Z$-boson transverse momentum, number of jets, and number of $b$ jets. The predictions from leading-order Monte Carlo generators and next-to-leading-order QCD calculations are found to be consistent with the measurements within experimental and theoretical uncertainties.

In-medium Yukawa theory is part of the thermodynamics of the standard model of particle physics and is one of the main building blocks of most effective field theories of fermionic systems. By computing its pressure we investigate the nonperturbative thermodynamics at finite temperature and density using the optimized perturbation theory framework. Our calculations are valid for arbitrary fermion and scalar masses, temperature, chemical potential, and not restricted to weak coupling. The model is considered in the presence as well as in the absence of condensates. Comparison with nonperturbative results shows that second-order perturbation theory fails in the first case but performs rather well when condensates are absent, even at high-temperature regimes.

Previous authors have considered the problem of the medium effects on single gluon bremsstrahlung associated with producing a high-energy particle in a finite, time-dependent QCD plasma. Working to leading logarithmic order, I show that the result for the bremsstrahlung gluon spectrum can be cast into a remarkably simple form in the general case. I similarly analyze the process of pair production. Also, I comment on the radius of convergence of the opacity expansion in cases where the leading-log approximation holds, showing that the opacity expansion does not converge when the thickness of the plasma is greater than roughly the bremsstrahlung formation time.

We construct brane solutions in 6-dimensional Einstein-Skyrme systems. A class of baby-Skyrmion solutions realizes warped compactification of the extra dimensions and gravity localization on the brane for the negative bulk cosmological constant. Coupling of the fermions with brane Skyrmions leads to brane localized fermions. In terms of the level crossing picture, emergence of the massive localized modes are observed. The nonlinear nature of Skyrmions brings richer information for the fermions’ level structure. It comprises doubly degenerate lowest plus single excited modes. Three generations of fundamental fermions are associated with this distinctive structure. The mass hierarchy of quarks or leptons appeared in terms of slightly deformed baby Skyrmions with topological charge three.

We derive a simple consistency relation from the running of the tensor-to-scalar ratio. This new relation is first order in the slow-roll approximation. While for single field models we can obtain what can be found by using other observables, multifield cases in general give nontrivial contributions dependent on the geometry of the field space and the inflationary dynamics, which can be probed observationally from this relation. The running of the tensor-to-scalar ratio may be detected by direct laser interferometer experiments.

This paper is a first step towards developing a formalism to optimally extract dark energy information from number counts using multiple cluster observation techniques. We use a Fisher matrix analysis to study the improvements in the joint dark energy and cluster mass-observables constraints resulting from combining cluster counts and clustering abundances measured with different techniques. We use our formalism to forecast the constraints in ${\Omega }_{\mathrm{DE}}$ and $w$ from combining optical and SZ cluster counting on a 4000 sq. degree patch of sky. We find that this cross-calibration approach yields $\sim 2$ times better constraints on ${\Omega }_{\mathrm{DE}}$ and $w$ compared to simply adding the Fisher matrices of the individually self-calibrated counts. The cross-calibrated constraints are less sensitive to variations in the mass threshold or maximum redshift range. A by-product of our technique is that the correlation between different mass-observables is well constrained without the need of additional priors on its value.

Dark matter neutralinos in the constrained minimal supersymmetric model (CMSSM) may account for the recent cosmic ray electron and positron observations reported by the PAMELA and ATIC experiments either through self annihilation or via decay. However, to achieve this, both scenarios require new physics beyond the “standard” CMSSM, and a unified explanation of the two experiments suggests a neutralino mass of order 700 GeV–2 TeV. A relatively light neutralino with mass around 100 GeV (300 GeV) can accommodate the PAMELA but not the ATIC observations based on a model of annihilating (decaying) neutralinos. We study the implications of these scenarios for Higgs and sparticle spectroscopy in the CMSSM and highlight some benchmark points. An estimate of neutrino flux expected from the annihilating and decaying neutralino scenarios is provided.

We consider the question whether a wormhole can be converted into a nonextremal quasiblack hole by a continuous change of parameters. In other words, we ask whether “black” wormholes can exist as end points of families of static wormhole geometries. The answer is negative since the corresponding limit is singular. Similar conclusions are valid also for other types of black hole mimickers. Our treatment is model independent and applies to any static geometries. We also find an asymptotic expression for the Kretschmann scalar for wormholes on the threshold of horizon formation. We point out complementarity between the ability of wormholes to mimic black holes and their ability to be traversable “in practice.”

Supergravity backgrounds with varying fluxes generated by fractional branes at nonisolated Calabi-Yau singularities had escaped a precise dual field theory interpretation so far. In the present work, considering the prototypical example of such models, the $\mathbb{C}\times {\mathbb{C}}^2/{\mathbb{Z}}_2$ orbifold, we propose a solution for this problem, and show that the known cascading solution corresponds to a vacuum on the Coulomb branch of the corresponding quiver gauge theory involving a sequence of strong coupling transitions reminiscent of the baryonic root of $\mathcal{N}=2$ supersymmetric quantum chromodynamics . We also find a slight modification of this cascading vacuum which upon mass deformation is expected to flow to the Klebanov-Strassler cascade. Finally, we discuss an infinite class of vacua on the Coulomb branch whose renormalization group flows include infinitely coupled conformal regimes, and explain their gravitational manifestation in terms of new geometric structures that we dub enhançon bearings. Repulson-free backgrounds dual to all the vacua we analyze are explicitly provided.

We evaluate the Casimir energy and force for a massive scalar field with general curvature coupling parameter, subject to Robin boundary conditions on two codimension-one parallel plates, located on a ($D+1$)-dimensional background spacetime with an arbitrary internal space. The most general case of different Robin coefficients on the two separate plates is considered. With independence of the geometry of the internal space, the Casimir forces are seen to be attractive for special cases of Dirichlet or Neumann boundary conditions on both plates and repulsive for Dirichlet boundary conditions on one plate and Neumann boundary conditions on the other. For Robin boundary conditions, the Casimir forces can be either attractive or repulsive, depending on the Robin coefficients and the separation between the plates, what is actually remarkable and useful. Indeed, we demonstrate the existence of an equilibrium point for the interplate distance, which is stabilized due to the Casimir force, and show that stability is enhanced by the presence of the extra dimensions. Applications of these properties in braneworld models are discussed. Finally, the corresponding results are generalized to the geometry of a piston of arbitrary cross section.