We report on a study of the measurement techniques used to determine the leptonic forward-backward asymmetry of top-antitop quark pairs in Tevatron experiments with a proton-antiproton initial state. Recently it was shown that a fit of the differential asymmetry as a function of $q_l{\eta }_l$ (where $q_l$ is the charge of the lepton from the cascade decay of the top quarks and ${\eta }_l$ is the final pseudorapidity of the lepton in the detector frame) to a hyperbolic tangent function can be used to extrapolate to the full leptonic asymmetry. We find this empirical method to well reproduce the results from current experiments and present arguments as to why this is the case. We also introduce two more models, based on Gaussian functions, that better model the $q_l{\eta }_l$ distribution. With our better understanding, we find that the asymmetry is mainly determined by the shift of the mean of the $q_l{\eta }_l$ distribution, the main contribution to the inclusive asymmetry comes from the region around $|q_l{\eta }_l|=1$, and the extrapolation from the detector-covered region to the inclusive asymmetry is stable via a multiplicative scale factor, giving us confidence in the previously reported experimental results.

In this paper, we calculate the soft-collisional energy loss of heavy quarks traversing the viscous quark-gluon plasma including the effects of a finite relaxation time ${\tau }_{\pi }$ on the energy loss. We find that the collisional energy loss depends appreciably on ${\tau }_{\pi }$. In particular, for typical values of the viscosity-to-entropy ratio, we show that the energy loss obtained using ${\tau }_{\pi }\ne 0$ can be $\sim 10\%$ larger than the one obtained using ${\tau }_{\pi }=0$. Moreover, we find that the energy loss obtained using the kinetic theory expression for ${\tau }_{\pi }$ is much larger than the one obtained with the ${\tau }_{\pi }$ derived from the anti–de Sitter/conformal field theory correspondence. Our results may be relevant in the modeling of heavy quark evolution through the quark-gluon plasma.

We study the single-spin asymmetries of pions produced in semi-inclusive deep-inelastic scattering on the longitudinally polarized nucleon targets. We particularly consider the effects of the twist-3 transverse-momentum dependent distribution functions $f_L^{\perp }$ and $h_L$ to the asymmetry. We calculate the asymmetric moment $A_{UL}^{\sin {\varphi }_h}$ for ${\pi }^{+}$, ${\pi }^{-}$, and ${\pi }^0$ produced off the proton target at HERMES and compare the results with the HERMES data. We also present the prediction of the same asymmetries for different pions at the kinematics of CLAS 5.5 GeV on a proton target, as well as at COMPASS on a deuteron target.

We discuss the recently presented Belle results on the decays $\mathrm{\Upsilon }(5S)\to \pi \pi \pi {\chi }_{bJ}(1P)$. The data indicate that in addition to the $\omega$ emission, $\mathrm{\Upsilon }(5S)\to \omega {\chi }_{bJ}$, there is a significant nonresonant background in the three pion spectrum. We suggest that a sizable fraction of this background may be associated with the cascade process $\mathrm{\Upsilon }(5S)\to \pi Z_b\to \pi \rho {\chi }_b$ involving the $Z_b(10610)$ and $Z_b(10650)$ resonances. If confirmed by the data, this would be the first observation of transition from the $Z_b$ resonances to lower bottomonium with emission of a light meson state different from a single pion, which may provide a new input in understanding of the internal dynamics of these resonances.

We study the effects of models with a warped extra dimension on rare charm decays. While the new degrees of freedom in these models are bounded above a few TeV, they can leave signatures in rare charm decays with their tiny Standard Model background. We look at several channels with leptons in the final state along with several asymmetries of both kinematical and dynamical nature. Charge-Parity-Time invariance is “usable” for analyzing the impacts of new dynamics in $D$ meson decays and in particular, rare decays of charm mesons.

In this work we have employed the Bethe-Salpeter equation (BSE) under covariant instantaneous ansatz to study electromagnetic decays of ground state equal mass vector mesons $\rho$, $\omega$, $\varphi$, $\psi$, and $Y$ through the process $V\to \gamma \to e^{+}+e^{-}$. We employ the generalized structure of the hadron-quark vertex function $\mathrm{\Gamma }$ that incorporates all Dirac structures from their complete set order by order in powers of the inverse of the meson mass. We have explicitly shown the derivation of this general form of this hadron-quark vertex function $\mathrm{\Gamma }$ (in terms of unknown coefficients) for a vector meson with the incorporation of all the Dirac structures (i.e., those dependent on external hadron momentum $P$, as well those dependent on internal hadron momentum $q$) as the solution of the full $4\times 4$ Bethe-Salpeter equation. The unknown coefficients multiplying the various Dirac structures are calculated by reducing the $4\times 4$ BSE to a determinantal form. These coefficients thus determined were also employed for the calculation of $f_V$ values and gave good agreement with data, as well as an acceptable solution of the full BSE.

We reevaluate the $B\to \rho l^{+}{\nu }_l$ decay width as a full $B\to \pi \pi l^{+}{\nu }_l$ four-particle decay, in which the two final pions are produced via an intermediate $\rho$ meson. The decay width can be written as a convolution of the $B\to \rho l^{+}{\nu }_l$ decay width, for an off-shell $\rho$, with the $\rho \to \pi \pi$ line shape. This allows us to fully incorporate the effects of the finite $\rho$ meson width and a better comparison with actual experiments. We use an Omnès representation to provide the dependence of the $B\to \rho$ semileptonic form factors on $q^2$. The Omnès subtraction constants and the overall normalization parameter $|V_{ub}|$ are fitted to light cone sum rules and lattice QCD theoretical form-factor calculations, in the low and high $q^2$ regions, respectively, together to the CLEO, BABAR, and Belle experimental partial branching fraction distributions. The extracted value from this global fit is $|V_{ub}|=(3.40\pm 0.15)\times 10^{-3}$, in agreement with $|V_{ub}|$ extracted using all other inputs in Cabibbo–Kobayashi–Maskawa fits and the exclusive semileptonic $B\to \pi$ channel, but showing a clear disagreement with $|V_{ub}|$ extracted from inclusive semileptonic $b\to u$ decays. As estimated by [U.-G. Meißner and W. Wang, J. High Energy Phys. 01 (2014) 107], taking into account the $\rho$ meson width effects and the actual acceptance of the experiments is essential to render the $|V_{ub}|$ determinations from exclusive $B\to \pi$ and $B\to \rho$ decays totally compatible.

A sample of $1.53\times {10}^9$ cosmic-ray-induced single muon events has been recorded at 225 m water equivalent using the MINOS near detector. The underground muon rate is observed to be highly correlated with the effective atmospheric temperature. The coefficient ${\alpha }_T$, relating the change in the muon rate to the change in the vertical effective temperature, is determined to be $0.428\pm 0.003(\text{stat}.)\pm 0.059(\text{syst}.)$. An alternative description is provided by the weighted effective temperature, introduced to account for the differences in the temperature profile and muon flux as a function of zenith angle. Using the latter estimation of temperature, the coefficient is determined to be $0.352\pm 0.003(\text{stat}.)\pm 0.046(\text{syst}.)$.

When the full connection of Weyl conformal gravity is varied instead of just the metric, the resulting vacuum field equations reduce to the vacuum Einstein equation, up to the choice of local units, if and only if the torsion vanishes. This result differs strongly from the usual fourth-order formulation of Weyl gravity.

Canonical quantum theories with discrete space may imply interesting effects. This paper presents a general effective description, paying due attention to the role of higher spatial derivatives in a local expansion and differences to higher time derivatives. In a concrete set of models, it is shown that spatial derivatives one order higher than the classical one are strongly restricted in spherically symmetric effective loop quantum gravity. Moreover, radial holonomy corrections alone cannot be anomaly free to this order.

This study is inspired by a scenario, in which the Standard Model enhanced by an additional dark-matter scalar could be extended up to the Planck scale, while accommodating the low measured value of the Higgs mass. To that end, we study a toy model for a gauge-singlet dark-matter scalar coupled to the Higgs-top-quark sector of the Standard Model. Using functional methods to derive renormalization group flow equations in that model, we examine several choices for the ultraviolet, bare potential in the Higgs-dark-matter sector. Our results indicate that the dark-matter scalar can decrease the lower bound on the Higgs mass in the Standard Model. We then use the fact that higher-order couplings which are driven to tiny values by the renormalization group flow towards low energies can easily be of order one at the ultraviolet cutoff scale. Our study indicates that the inclusion of these couplings can significantly increase the ultraviolet cutoff scale and therefore the range of validity of the model while yielding a low value for the Higgs mass in the infrared. This is achieved within a setting where the dark-matter scalar accounts for the complete dark-matter relic density in our Universe.

In this paper, we consider the problem of test particles and test scalar fields propagating on the background of a class of wormhole space-times. For test particles, we solve for arbitrary causal geodesics in terms of integrals which are solved numerically. These integrals are parametrized by the radius and shape of the wormhole throat as well as the initial conditions of the geodesic trajectory. In terms of these parameters, we compute the conditions for the geodesic to traverse the wormhole, to be reflected by the wormhole’s potential or to be captured on an unstable bound orbit at the wormhole’s throat. These causal geodesics are visualized by embedding plots in Euclidean space in cylindrical coordinates. For massless test scalar fields, we compute transmission coefficients and quasinormal modes for arbitrary coupling of the field to the background geometry in the WKB approximation. We show that solutions of the scalar wave equation are stable only when the coupling constant satisfies $\xi <1/2$. This analysis is interesting since recent computations of self-interactions of a static scalar field in wormhole space-times reveal some anomalous dependence on the coupling constant such as the existence of an infinite discrete set of poles. We show that this pathological behavior of the self-field is an artifact of computing the interaction for values of the coupling constant that do not lie in the domain of stability.

We examine the compatibility of the mirror matter concept with the nonorientable wormholes. If any particle (or classical object) is traversing through the nonorientable wormhole, it turns into a corresponding mirror particle and vice versa. It is shown that a critical sonic point in the hydrodynamical flow of the perfect fluid is located exactly at the wormhole throat. This means that wormholes are traversable for the fluid. We discuss the possible astrophysical signatures of the presence of nonorientable wormholes in the Universe. Some nontrivial aspects of the nonorientable wormhole electrodynamics are considered.

We develop a numerical solver that extends the computational framework considered in [Phys. Rev. D 65, 084016 (2002)] to include scalar perturbations of nonrotating black holes. The nonlinear Einstein-Klein-Gordon equations for a massless scalar field minimally coupled to gravity are solved in two spatial dimensions. The numerical procedure is based on the ingoing light-cone formulation for an axially and reflection-symmetric spacetime. The solver is second-order accurate and was validated in different ways. We use for calibration an auxiliary 1D solver with the same initial and boundary conditions and the same evolution algorithm. We reproduce the quasinormal modes for the massless scalar field harmonics $\ell =0$, 1, and 2. For these same harmonics, in the linear approximation, we calculate the balance of energy between the black hole and the world tube. As an example of nonlinear harmonic generation, we show the distortion of a marginally trapped two-surface approximated as a q-boundary and based upon the harmonic $\ell =2$. Additionally, we study the evolution of the $\ell =8$ harmonic in order to test the solver in a spacetime with a complex angular structure. Further applications and extensions are briefly discussed.

The well-known BTZ black hole solution of ($2+1$) Einstein’s gravity, in the presence of a cosmological constant, is treated both at the classical and quantum level. Classically, the imposition of the two manifest local Killing fields of the BTZ geometry at the level of the full action results in a minisuperspace constraint action with the radial coordinate playing the role of the independent dynamical variable. The Noether symmetries of this reduced action are then shown to completely determine the classical solution space, without any further need to solve the dynamical equations of motion. At a quantum mechanical level, all the admissible sets of the quantum counterparts of the generators of the above-mentioned symmetries are utilized as supplementary conditions acting on the wave function. These additional restrictions, in conjunction with the Wheeler-DeWitt equation, help to determine (up to constants) the wave function which is then treated semiclassically, in the sense of Bohm. The ensuing spacetimes are either identical to the classical geometry, thus exhibiting a good correlation of the corresponding quantization to the classical theory, or are less symmetric but contain the classical topological constants $M$, $J$ as locally essential.

It is shown that Kerr-Newman black holes can support linear charged scalar fields in their exterior regions. To that end, we solve analytically the Klein-Gordon wave equation for a stationary charged massive scalar field in the background of a near-extremal Kerr-Newman black hole. In particular, we derive a simple analytical formula which describes the physical properties of these stationary bound-state resonances of the charged massive scalar fields in the Kerr-Newman black-hole spacetime.

We generalize the Galileon duality to any single scalar field Lagrangian coupled locally to any matter field. Under the duality, a generalized Galileon maps into another generalized Galileon via a one-parameter group of transformations, with only a simple modification of the Lagrangian functions. We find a special class of generalized Galileons for which the duality is a symmetry of the action. We further extend the duality to the case of vector fields and give the dual formulations of the Maxwell and Proca theories. We include arbitrary local couplings to matter fields and show that the duality always maps a local interacting theory into a local interacting theory. We also discuss the coupling to gravity and uncover a new class of Lorentz-invariant massive theories which map into themselves under the duality. Finally, we show that the duality can be used to map solutions of a theory with superluminal (luminal) group velocity into one with luminal (subluminal) group velocity. We find that the duality nevertheless preserves the classical causal structure and emphasize the need to include the quantum corrections to ascertain relativistic causality.

In this paper we calculate the effect of acceleration on the decay and excitation rates of scalar fields into a final state of arbitrary multiplicity. The analysis is carried out using standard field operators as well as an Unruh-DeWitt detector. Using the equivalence of the two methods, we show how to correctly set up the computation and interpret the results in terms of the particle content of the initial and final state Rindler and Minkowski spacetimes. We find the dominant transition pathway, and thus final state multiplicity, is acceleration dependent. The formalisms developed are then used to analyze the electron and muon system. We compute the transition rates and lifetimes for accelerated electrons and muons as well as the branching fractions for muon decay.

We show that, in the presence of massive neutrinos, the Galileon gravity model provides a very good fit to the current cosmic microwave background (CMB) temperature, CMB lensing and baryonic acoustic oscillation data. This model, which we dub $\nu \text{Galileon}$, when assuming its stable attractor background solution, contains the same set of free parameters as lambda cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$), although it leads to different expansion dynamics and nontrivial gravitational interactions. The data provide compelling evidence ($\gtrsim 6\sigma$) for nonzero neutrino masses, with $\mathrm{\Sigma }{m}_{\nu }\gtrsim 0.4\mathrm{eV}$ at the $2\sigma$ level. Upcoming precision terrestrial measurements of the absolute neutrino mass scale therefore have the potential to test this model. We show that CMB lensing measurements at multipoles $l\lesssim 40$ will be able to discriminate between the $\nu \text{Galileon}$ and $\mathrm{\Lambda }\mathrm{CDM}$ models. Unlike $\mathrm{\Lambda }\mathrm{CDM}$, the $\nu \text{Galileon}$ model is consistent with local determinations of the Hubble parameter. The presence of massive neutrinos lowers the value of ${\sigma }_8$ substantially, despite of the enhanced gravitational strength on large scales. Unlike $\mathrm{\Lambda }\mathrm{CDM}$, the $\nu \text{Galileon}$ model predicts a negative ISW effect, which is difficult to reconcile with current observational limits.

Comparing the latest observed abundances of ${}^4\mathrm{He}$ and D, we make a ${\chi }^2$ analysis to see whether it is possible to reconcile primordial nucleosynthesis using the up-to-date nuclear data of NACRE II and the mean life of neutrons. If we adopt the observational data of ${}^4\mathrm{He}$ by Izotov et al. [Astron. Astrophys. 558, A57 (2013)], we find that it is impossible to get a reasonable agreement with the standard big-bang nucleosynthesis. However, by including degenerate neutrinos, we succeed in obtaining consistent constraints between the neutrino degeneracy and the baryon-to-photon ratio from a detailed comparison of calculated abundances with the observational data of ${}^4\mathrm{He}$ and D: the baryon-to-photon ratio in units of ${10}^{-10}$ is found to be in the range $6.02\lesssim {\eta }_{10}\lesssim 6.54$ for the specified parameters of neutrino degeneracy.