We present a measurement of $p\overline{p}\to Z\gamma \to {\ell }^{+}{\ell }^{-}\gamma$ ($\ell =e$, $\mu$) production with a data sample corresponding to an integrated luminosity of $6.2{\mathrm{fb}}^{-1}$ collected by the D0 detector at the Fermilab Tevatron $p\overline{p}$ Collider. The results of the electron and muon channels are combined, and we measure the total production cross section and the differential cross section $d\sigma /d{p}_T^{\gamma }$, where $p_T^{\gamma }$ is the momentum of the photon in the plane transverse to the beam line. The results obtained are consistent with the standard model predictions from next-to-leading order calculations. We use the transverse momentum spectrum of the photon to place limits on anomalous $ZZ\gamma$ and $Z\gamma \gamma$ couplings.

I derive a rigorous relation between the expectation value of the transverse component of the Belinfante version of the angular momentum $⟨J_T^{\mathrm{bel}}⟩$ of a quark in a transversely polarized nucleon in terms of the generalized parton distributions $H$ and $E$, namely $⟨J_T^{\mathrm{bel}}(\mathrm{\text{quark}})⟩=[1/2M][P_0{\int }_{-1}^{1}dxx{E}_q(x,0,0)+M{\int }_{-1}^{1}dxx{H}_q(x,0,0)]$, where $P_0$ is the energy of the nucleon and where quark implies the sum of quark and antiquark of a given flavor. A similar relation holds for gluons. The result is remarkably similar to Ji’s relation for the case of longitudinal polarization, whose content I spell out precisely, and which has proved extremely interesting in testing models, in comparing different definitions of quark and gluon angular momentum, and in comparing with lattice calculations. The transverse relation can offer additional insights into all of these, by extending them to the new domain of transversely polarized and moving nucleons.

We explore the reconstruction of the gravitational lensing field of the cosmic microwave background in real space. We show that very little statistical information is lost when estimators of short range on the celestial sphere are used in place of the customary estimators in harmonic space, which are nonlocal and in principle require a simultaneous analysis of the entire sky without any cuts or excisions. Because virtually all the information relevant to lensing reconstruction lies on angular scales close to the resolution scale of the sky map, the gravitational lensing convergence and shear fields (which unlike the deflection field or lensing potential are directly related to the observations in a local manner) may be reconstructed by means of quadratic combinations involving only closely separated pixels. Even though harmonic space provides a more natural context for understanding lensing reconstruction theoretically, the real space methods developed here have the virtue of being faster to implement and are likely to prove useful for analyzing realistic maps containing a galactic cut and possibly numerous small excisions to exclude point sources that cannot be reliably subtracted.

We extend the Collins-Soper-Sterman (CSS) formalism to apply it to the spin dependence governed by the Sivers function. We use it to give a correct numerical QCD evolution of existing fixed-scale fits of the Sivers function. With the aid of approximations useful for the nonperturbative region, we present the results as parametrizations of a Gaussian form in transverse-momentum space, rather than in the Fourier conjugate transverse coordinate space normally used in the CSS formalism. They are specifically valid at small transverse momentum. Since evolution has been applied, our results can be used to make predictions for Drell-Yan and semi-inclusive deep inelastic scattering at energies different from those where the original fits were made. Our evolved functions are of a form that they can be used in the same parton-model factorization formulas as used in the original fits, but now with a predicted scale dependence in the fit parameters. We also present a method by which our evolved functions can be corrected to allow for twist-3 contributions at large parton transverse momentum.

We extend our investigation on a possible de Sitter symmetry breaking mechanism in nonlinear sigma models. The scale invariance of the quantum fluctuations could make the cosmological constant time dependent signaling the de Sitter symmetry breaking. To understand such a symmetry breaking mechanism, we investigate the energy-momentum tensor. We show that the leading infrared logarithms cancel to all orders in perturbation theory in a generic nonlinear sigma model. When the target space is an $N$ sphere, the de Sitter symmetry is preserved in the large $N$ limit. For a less symmetric target space, the infrared logarithms appear at the three-loop level. However, there is a counterterm to precisely cancel it. The leading infrared logarithms do not cancel for higher derivative interactions. We investigate such a model in which the infrared logarithms first appear at the three-loop level. A nonperturbative investigation in the large $N$ limit shows that they eventually grow as large as the one-loop effect.

The late inspiral, merger, and ringdown of a black hole-neutron star (BHNS) system can provide information about the neutron-star equation of state (EOS). Candidate EOSs can be approximated by a parametrized piecewise-polytropic EOS above nuclear density, matched to a fixed low-density EOS; and we report results from a large set of BHNS inspiral simulations that systematically vary two parameters. To within the accuracy of the simulations, we find that, apart from the neutron-star mass, a single physical parameter $\Lambda$, describing its deformability, can be extracted from the late inspiral, merger, and ringdown waveform. This parameter is related to the radius, mass, and $\ell =2$ Love number, $k_2$, of the neutron star by $\Lambda =2k_2{R}^5/3M_{\mathrm{NS}}^5$, and it is the same parameter that determines the departure from point-particle dynamics during the early inspiral. Observations of gravitational waves from BHNS inspiral thus restrict the EOS to a surface of constant $\Lambda$ in the parameter space, thickened by the measurement error. Using various configurations of a single Advanced LIGO detector, we find that ${\Lambda }^{1/5}$ or equivalently $R$ can be extracted to 10–50% accuracy from single events for mass ratios of $Q=2$ and 3 at a distance of 100 Mpc, while with the proposed Einstein Telescope, EOS parameters can be extracted to accuracy an order of magnitude better.

Laser Interferometer Space Antenna (LISA) Pathfinder is a science and technology demonstrator of the European Space Agency within the framework of its LISA mission, the latter aiming to be the first space-borne gravitational wave observatory. The payload of LISA Pathfinder is the so-called LISA Technology Package, which is designed to measure relative accelerations between two test masses in nominal free fall. The diagnostics subsystem consists of several modules, one of which is the magnetic diagnostics unit. Its main function is the assessment of the differential acceleration noise between the test masses due to magnetic effects. This subsystem is composed of two onboard coils intended to produce controlled magnetic fields at the location of the test masses. These magnetic fields couple with the remanent magnetic moment and susceptibility and produce forces and torques on the test masses. These, in turn, produce kinematic excursions of the test masses which are sensed by the onboard interferometer. We prove that adequately processing these excursions, the magnetic properties of the test masses can be estimated using classical multiparameter estimation techniques. Moreover, we show that special processing procedures to minimize the effect of the multichannel cross-talks are needed. Finally, we demonstrate that the quality of our estimates is frequency-dependent. We also suggest that using a multiple frequency experiment, the global estimate can be obtained in such a way that the results of the magnetic experiment are more reliable. Finally, using our procedure, we compute the contribution of the magnetic noise to the total proof-mass acceleration noise.

We present results for the spectrum of light and strange mesons on configurations with two flavors of mass-degenerate Chirally Improved sea quarks. The calculations are performed on seven ensembles of lattice size ${16}^3\times 32$ at three different gauge couplings and with pion masses ranging from 250 to 600 MeV. To reliably extract excited states, we use the variational method with an interpolator basis containing both Gaussian and derivative quark sources. Both conventional and exotic channels up to spin 2 are considered. Strange quarks are treated within the partially quenched approximation. For kaons we investigate the mixing of interpolating fields corresponding to definite $C$-parity in the SU(3) limit. This enlarged basis allows for an improved determination of the low-lying kaon spectrum. In addition to masses we also extract the ratio of the pseudoscalar decay constants of the kaon and pion and obtain $F_K/F_{\pi }=1.215(41)$. The results presented here include some ensembles from previous publications and the corresponding results supersede the previously published values.

Motivated by the ongoing measurements of the Primakoff process ${\pi }^{-}{\gamma }^{*}\to {\pi }^{-}{\pi }^0$ by the COMPASS Collaboration at CERN, the transition form factor for the canonical anomalous process ${\gamma }^{*}\to {\pi }^{+}{\pi }^0{\pi }^{-}$ is calculated in a constituent quark-loop model. The simplest contribution to this process is the quark “box” amplitude. In the present paper we also explicitly include the vector meson degrees of freedom, i.e., the $\rho$ and the $\omega$, thus giving rise to additional, resonant contributions. We find that in order to satisfy the axial anomaly result, a further subtraction in the resonant part is needed. The results are then compared with the vector meson dominance model as well as the Dyson-Schwinger calculations, the chiral perturbation theory result, and the available data.

Results are presented on the production of jets of particles in association with a $Z/{\gamma }^{*}$ boson, in proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$ with the ATLAS detector. The analysis includes the full 2010 data set, collected with a low rate of multiple proton-proton collisions in the accelerator, corresponding to an integrated luminosity of $36{\mathrm{pb}}^{-1}$. Inclusive jet cross sections in $Z/{\gamma }^{*}$ events, with $Z/{\gamma }^{*}$ decaying into electron or muon pairs, are measured for jets with transverse momentum $p_T>30\mathrm{GeV}$ and jet rapidity $|y|<4.4$. The measurements are compared to next-to-leading-order perturbative QCD calculations, and to predictions from different Monte Carlo generators implementing leading-order matrix elements supplemented by parton showers.

In this paper a model describing fermions and gauge field localized on a domain wall is considered. The zero-mode sector of the model reproduces four-dimensional spinor electrodynamics. It is shown that in the resulting four-dimensional effective theory the lowest-order renormalized amplitude of the elastic $\gamma \gamma$ scattering process is divergent due to the contributions of higher modes and thus such a scenario can not be considered as a realistic mechanism for fields localization on a domain wall.

We construct exactly solvable models of twisted carbon nanotubes via supersymmetry, by applying the matrix Darboux transformation. We derive the Green’s function for these systems and compute the local density of states . Explicit examples of twisted carbon nanotubes are produced, where the backscattering is suppressed and bound states are present. We find that the local density of states decreases in the regions where the bound states are localized. Dependence of bound-state energies on the asymptotic twist of the nanotubes is determined. We also show that each of the constructed unextended first-order matrix systems possesses a proper nonlinear hidden supersymmetric structure with a nontrivial grading operator.

In [M. Nouri-Zonoz and B. Nazari, Phys. Rev. D 82, 044047 (2010)], we investigated the response of vacuum energy to a gravitational field by considering a Casimir apparatus in a weak gravitational field. Our approach was based on a conjecture involving the interpretation of spacetime as a refractive medium and its effect on vacuum energy composed of virtual massless scalar particles. There it was shown how the case of virtual photons as the constituents of vacuum could be inferred from that of the massless scalar field. Here we explicitly show how the same conjecture applies to the electromagnetic vacuum composed of virtual photons. Specifically, we show that the boundary conditions imposed on the components of the vector field, decomposed into two scalar fields, result in the same frequency shift for photons. Using the same decomposition and employing our conjecture, we also calculate the electromagnetic energy density for the Casimir apparatus in a weak gravitational field.

This paper presents an in-depth study of how to estimate the sensitivity of searches for gravitational-wave pulsars—rapidly rotating neutron stars which emit quasisinusoidal gravitational waves. It is particularly concerned with searches over a wide range of possible source parameters, such as searches over the entire sky and broad frequency bands. Traditional approaches to estimating the sensitivity of such searches use either computationally expensive Monte Carlo simulations, or analytic methods which sacrifice accuracy by making an unphysical assumption about the population of sources being searched for. This paper develops a new, analytic method of estimating search sensitivity which does not rely upon this unphysical assumption. Unlike previous analytic methods, the new method accurately predicts the sensitivity obtained using Monte Carlo simulations, while avoiding their computational expense. The change in estimated sensitivity due to properties of the search template bank and the geographic configuration of the gravitational-wave detector network are also investigated.

We investigate the spin contribution to light baryon ground states in three inequivalent large-$N$ limits: ’t Hooft, QCD antisymmetric and QCD symmetric. Our work is based on a previous study where we have analyzed a constituent quark model with a relativistic Hamiltonian containing a stringlike confinement and a one-gluon exchange term. In this work, two spin-dependent potentials are considered and treated as perturbations: the color magnetic interaction stemming from the one-gluon exchange process and the chiral (or Goldstone) boson exchange interaction. We analytically prove that the spin contributions scale like $S(S+1)/n_q$, where $S$ is the total spin and $n_q$ is the number of quark, in agreement with diagrammatic methods. Both potentials yield also $S$-independent contributions which scale at most as $\mathrm{O}(n_q)$.

We investigate the transverse quark spin densities of the nucleon with the lowest moment within the framework of the $SU(3)$ chiral quark-soliton model, emphasizing the strange quark spin density. Based on previous results of the vector and tensor form factors, we are able to determine the impact-parameter dependent probability densities of transversely polarized quarks in an unpolarized nucleon as well as those of unpolarized quarks in a transversely polarized nucleon. We find that the present numerical results for the transverse spin densities of the up and down quarks are in good agreement with those of the lattice calculation. We predict the transverse spin densities of the strange quark. It turns out that the polarized strange quark is noticeably distorted in an unpolarized proton.

We investigate the quasinormal mode of the perturbation of the scalar field interacting with the electromagnetic field in the backgrounds of neutral AdS black hole, the Reissner-Nordstrom AdS black hole, and the Born-Infeld AdS black hole. We study the influence of the electric charge $Q$, the coupling $q$ between electromagnetic and scalar field, and the Born-Infeld parameter $b$ on the quasinormal frequencies of the scalar perturbations. We observe the possible growing mode when the perturbation of the scalar field strongly couples to the electromagnetic field. When the electromagnetic field becomes nonlinear described by the Born-Infeld electrodynamics, the nonlinearity described by the Born-Infeld parameter can hinder the instability to happen in the scalar perturbation. The quasinormal behavior of the scalar field perturbation can help us further understand the physics in the holographic superconductor.

Eguchi-Hanson solitons are odd-dimensional generalizations of the four-dimensional Eguchi-Hanson metric and are asymptotic to ${\mathrm{AdS}}_5/{\mathbb{Z}}_p$ when the cosmological constant is either positive or negative. We find soliton solutions to Lovelock gravity in 5 dimensions that are generalizations of these objects.