We study the next-to-leading order perturbative QCD corrections to the transverse momentum-weighted Sivers asymmetry in semi-inclusive hadron production in lepton-proton deep inelastic scattering. The corresponding differential cross section is evaluated as a convolution of a twist-three quark-gluon correlation function, often referred to as Qiu-Sterman function, the usual unpolarized fragmentation function, and a hard coefficient function. By studying the collinear divergence structure, we identify the evolution kernel for the Qiu-Sterman function. The hard coefficient function, which is finite and free of any divergence, is evaluated at one-loop order.

Apparent regularities in fermion masses and mixings are often associated with physics at a high flavor scale, especially in the context of discrete flavor symmetries. One of the main reasons for that is that the correct vacuum alignment requires usually some high scale mechanism to be phenomenologically acceptable. Contrary to this expectation, we present in this paper a renormalizable radiative neutrino mass model with an $A_4$ flavor symmetry in the lepton sector, which is broken at the electroweak scale. For that we use a novel way to achieve the vacuum expectation value alignment via an extended symmetry in the flavon potential proposed before by two of the authors. We discuss various phenomenological consequences for the lepton sector and show how the remnants of the flavor symmetry suppress large lepton flavor violating processes. The model naturally includes a dark matter candidate, whose phenomenology we outline. Finally, we sketch possible extensions to the quark sector and discuss its implications for the LHC, especially how an enhanced diphoton rate for the resonance at 125 GeV can be explained within this model.

We investigate the finite temperature expectation values of the charge and current densities for a complex scalar field with nonzero chemical potential in the background of a flat spacetime with spatial topology $R^p\times (S^1{)}^q$. Along compact dimensions quasiperiodicity conditions with general phases are imposed on the field. In addition, we assume the presence of a constant gauge field which, due to the nontrivial topology of background space, leads to Aharonov-Bohm-like effects on the expectation values. By using the Abel-Plana-type summation formula and zeta function techniques, two different representations are provided for both the current and charge densities. The current density has nonzero components along the compact dimensions only and, in the absence of a gauge field, it vanishes for special cases of twisted and untwisted scalar fields. In the high-temperature limit, the current density and the topological part in the charge density are linear functions of the temperature. The Bose-Einstein condensation for a fixed value of the charge is discussed. The expression for the chemical potential is given in terms of the lengths of compact dimensions, temperature, and gauge field. It is shown that the parameters of the phase transition can be controlled by tuning the gauge field. The separate contributions to the charge and current densities coming from the Bose-Einstein condensate and from excited states are also investigated.

We study spherically symmetric solutions of the cubic covariant Galileon model in curved spacetime in the presence of a matter source, in the test scalar field approximation. We show that a cosmological time evolution of the Galileon field gives rise to an induced matter-scalar coupling, due to the Galileon-graviton kinetic braiding, therefore the solution for the Galileon field is nontrivial even if the bare matter-scalar coupling constant is set to zero. The local solution crucially depends on the asymptotic boundary conditions, and in particular, Minkowski and de Sitter asymptotics correspond to different branches of the solution. We study the stability of these solutions, namely, the well posedness of the Cauchy problem and the positivity of energy for scalar and tensor perturbations, by diagonalizing the kinetic terms of the spin-2 and spin-0 degrees of freedom. In addition, we find that in the presence of a cosmological time evolution of the Galileon field, its kinetic mixing with the graviton leads to a friction force resulting in efficient damping of scalar perturbations within matter.

We use a dynamical systems analysis to investigate the future behavior of Einstein-Aether cosmological models with a scalar field coupling to the expansion of the aether and a noninteracting perfect fluid. The stability of the equilibrium solutions are analyzed, and the results are compared with the standard inflationary cosmological solutions and previously studied cosmological Einstein-aether models.

We derive covariant expressions for the one-loop vacuum polarization induced by a charged scalar on de Sitter background. Two forms are employed: one in which two covariant derivatives act on de Sitter-invariant basis tensors multiplied by scalar structure functions, and the other in which four covariant derivatives act on a single basis tensor times a structure function. The second representation permits the correction to dynamical photons to be expressed as a surface integral, which raises the important question of what sorts of effects can be absorbed into corrections of the initial state. Results are obtained for charged, minimally coupled scalars which are either massless or else light. The former show de Sitter breaking whereas the latter are de Sitter invariant. However, the de Sitter-invariant formulation does not seem useful, even when it is possible. Our work has two important physical consequences: (1) an upcoming computation of the vacuum polarization from inflationary gravitons should be expressed using the old, noncovariant formalism, and (2) one should re-examine the conclusion of a previous study of the effect of inflationary scalars on gravitons.

We study direct detection of dark matter in a supersymmetric model where most supersymmetric particles have very high-scale masses beyond the weak scale. In the scenario, a Wino-like or a Higgsino-like neutralino is a good candidate for the dark matter in the Universe. The neutralino scatters off nuclei by a Higgs boson exchange diagram and also electroweak loop diagrams. It is found that the elastic-scattering cross section with nuclei is enhanced or suppressed due to constructive or deconstructive interference among the diagrams. Such a cross section is within the reach of future experiment in some parameter region.

We calculate the strange quark content of the nucleon $⟨N|\overline{s}s|N⟩$ in $2+1$ -flavor lattice QCD. Chirally symmetric overlap fermion formulation is used to avoid the contamination from up and down quark contents due to an operator mixing between strange and light scalar operators, $\overline{s}s$ and $\overline{u}u+\overline{d}d$. At a lattice spacing $a=0.112(1)\mathrm{fm}$, we perform calculations at four values of degenerate up and down quark masses $m_{ud}$, which cover a range of the pion mass $M_{\pi }\simeq 300–540\mathrm{MeV}$. We employ two different methods to calculate $⟨N|\overline{s}s|N⟩$. One is a direct method where we calculate $⟨N|\overline{s}s|N⟩$ by directly inserting the $\overline{s}s$ operator. The other is an indirect method where $⟨N|\overline{s}s|N⟩$ is extracted from a derivative of the nucleon mass in terms of the strange quark mass. With these two methods we obtain consistent results for $⟨N|\overline{s}s|N⟩$ with each other. Our best estimate $f_{T_s}=m_s⟨N|\overline{s}s|N⟩/M_N=0.009(15{)}_{\mathrm{stat}}(16{)}_{\mathrm{sys}}$ is in good agreement with our previous studies in two-flavor QCD.

The roles of light $\rho$ and $\omega$ vector mesons in the Skyrmion are investigated in a chiral Lagrangian derived from the hidden local symmetry (HLS) up to $O(p^4)$ including the homogeneous Wess-Zumino terms. We write a general “master formula” that allows us to determine the parameters of the HLS Lagrangian from a class of holographic QCD models valid at the large-$N_c$ and -$\lambda$ (’t Hooft constant) limit by integrating out the infinite towers of vector and axial-vector mesons other than the lowest $\rho$ and $\omega$ mesons. Within this approach we find that the physical properties of the Skyrmion as the solitonic description of baryons are independent of the HLS parameter $a$. Therefore the only parameters of the model are the pion decay constant and the vector-meson mass. Once determined in the meson sector, we have a totally parameter-free theory that allows us to study unequivocally the role of light vector mesons in the Skyrmion structure. We find, as suggested by Sutcliffe, that the inclusion of the $\rho$ meson reduces the soliton mass, which makes the Skyrmion come closer to the Bogomol’nyi-Prasad-Sommerfield soliton, but the role of the $\omega$ meson is found to increase the soliton mass. In stark contrast, the $\Delta \mathrm{\text{−}}N$ mass difference, which is determined by the moment of inertia in the adiabatic collective quantization of the Skyrmion, is increased by the $\rho$ vector meson, while it is reduced by the inclusion of the $\omega$ meson. All these observations show the importance of the $\omega$ meson in the properties of the nucleon and nuclear matter in the Skyrme model.

Predictions for the hyperfine splitting of 2S bottomonia are compared with the two recent experimental candidates for the ${\eta }_b(2\mathrm{S})$. The smaller splitting of the Belle state is consistent with unquenched lattice QCD computations, many potential models, and a model-independent relation which works well for charmonia. The larger splitting for the state extracted from CLEO data is inconsistent with most predictions.

Determination of the neutrino mass hierarchy using a reactor neutrino experiment at $\sim 60\mathrm{km}$ is analyzed. Such a measurement is challenging due to the finite detector resolution, the absolute energy scale calibration, and the degeneracies caused by current experimental uncertainty of $|\Delta m_{32}^2|$. The standard ${\chi }^2$ method is compared with a proposed Fourier transformation method. In addition, we show that for such a measurement to succeed, one must understand the nonlinearity of the detector energy scale at the level of a few tenths of percent.

Using $106\times {10}^6$ ${\psi }^{\prime }$ decays collected with the BESIII detector at the BEPCII, three decays of ${\chi }_{cJ}$ ($J=0$, 1, 2) with baryon pairs ($\Lambda \overline{\Lambda }$, ${\Sigma }^0{\overline{\Sigma }}^0$, ${\Sigma }^{+}{\overline{\Sigma }}^{-}$) in the final state have been studied. The branching fractions are measured to be $\mathcal{B}({\chi }_{c0,1,2}\to \Lambda \overline{\Lambda })=(33.3\pm 2.0\pm 2.6)\times {10}^{-5}$, $(12.2\pm 1.1\pm 1.1)\times {10}^{-5}$, $(20.8\pm 1.6\pm 2.3)\times {10}^{-5}$; $\mathcal{B}({\chi }_{c0,1,2}\to {\Sigma }^0{\overline{\Sigma }}^0)=(47.8\pm 3.4\pm 3.9)\times {10}^{-5}$, $(3.8\pm 1.0\pm 0.5)\times {10}^{-5}$, $(4.0\pm 1.1\pm 0.5)\times {10}^{-5}$; and $\mathcal{B}({\chi }_{c0,1,2}\to {\Sigma }^{+}{\overline{\Sigma }}^{-})=(45.4\pm 4.2\pm 3.0)\times {10}^{-5}$, $(5.4\pm 1.5\pm 0.5)\times {10}^{-5}$, $(4.9\pm 1.9\pm 0.7)\times {10}^{-5}$, where the first error is statistical and the second is systematic. Upper limits on the branching fractions for the decays of ${\chi }_{c1,2}\to {\Sigma }^0{\overline{\Sigma }}^0$, ${\Sigma }^{+}{\overline{\Sigma }}^{-}$ are estimated to be $\mathcal{B}({\chi }_{c1}\to {\Sigma }^0{\overline{\Sigma }}^0)<6.2\times {10}^{-5}$, $\mathcal{B}({\chi }_{c2}\to {\Sigma }^0{\overline{\Sigma }}^0)<6.5\times {10}^{-5}$, $\mathcal{B}({\chi }_{c1}\to {\Sigma }^{+}{\overline{\Sigma }}^{-})<8.7\times {10}^{-5}$ and $\mathcal{B}({\chi }_{c2}\to {\Sigma }^{+}{\overline{\Sigma }}^{-})<8.8\times {10}^{-5}$ at the 90% confidence level.

Using a sample of 225.3 million $J/\psi$ events collected with the BESIII detector at the BEPCII $e^{+}{e}^{-}$ collider in 2009, searches for the decays of $\eta$ and ${\eta }^{\prime }\to {\pi }^{+}{e}^{-}{\overline{\nu }}_e+\mathrm{c}.\mathrm{c}.$ in $J/\psi \to \varphi \eta$ and $\varphi {\eta }^{\prime }$ are performed. The $\varphi$ signals, which are reconstructed in $K^{+}{K}^{-}$ final states, are used to tag $\eta$ and ${\eta }^{\prime }$ semileptonic decays. No signals are observed for either $\eta$ or ${\eta }^{\prime }$, and upper limits at the 90% confidence level are determined to be $7.3\times {10}^{-4}$ and $5.0\times {10}^{-4}$ for the ratios $\frac{\mathcal{B}(\eta \to {\pi }^{+}{e}^{-}{\overline{\nu }}_e+\mathrm{c}.\mathrm{c}.)}{\mathcal{B}(\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0)}$ and $\frac{\mathcal{B}({\eta }^{\prime }\to {\pi }^{+}{e}^{-}{\overline{\nu }}_e+\mathrm{c}.\mathrm{c}.)}{\mathcal{B}({\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}\eta )}$, respectively. These are the first upper-limit values determined for $\eta$ and ${\eta }^{\prime }$ semileptonic weak decays.

We search for di-muon decays of a low-mass Higgs boson ($A^0$) produced in radiative ${\rm Y}(1S)$ decays. The ${\rm Y}(1S)$ sample is selected by tagging the pion pair in the ${\rm Y}(2S,3S)\to {\pi }^{+}{\pi }^{-}{\rm Y}(1S)$ transitions, using a data sample of $92.8\times {10}^6$ ${\rm Y}(2S)$ and $116.8\times {10}^6$ ${\rm Y}(3S)$ events collected by the BABAR detector. We find no evidence for $A^0$ production and set 90% confidence level upper limits on the product branching fraction $\mathcal{B}({\rm Y}(1S)\to \gamma A^0)\times \mathcal{B}(A^0\to {\mu }^{+}{\mu }^{-})$ in the range of $(0.28-9.7)\times {10}^{-6}$ for $0.212\le m_{A^0}\le 9.20\mathrm{GeV}/c^2$. The results are combined with our previous measurements of ${\rm Y}(2S,3S)\to \gamma A^0$, $A^0\to {\mu }^{+}{\mu }^{-}$ to set limits on the effective coupling of the $b$ quark to the $A^0$.

We consider the possibility of a bosonic (meta)stabilization of a cosmic gauge string loop due to the presence of a gas of low-mass bosonic particles which become trapped within the string core. This boson gas exerts a pressure which tends to counteract the string tension, allowing a circular string loop to find a finite equilibrium radius, provided that gas particles do not escape the string core. However, high-energy bosons do escape, and, consequently, the loop shrinks, and the temperature rises. Estimates indicate that the bosonic stabilization mechanism is ineffective, and the loop is unstable against decay.

We consider a version of the McLerran-Venugopalan model by Lam and Mahlon where confinement is implemented via colored noise in the infrared. This model does not assume an infinite momentum frame, hence the boosted nuclei are not infinitely thin. Instead, the nuclei have a finite extension in the longitudinal direction and therefore depend on the longitudinal coordinate. In this fully three-dimensional framework an x dependence of the gluon distribution function emerges naturally. In order to fix the parameters of the model, we calculate the gluon distribution function and compare it with the JR09 parametrization of the data. We explore the parameter space of the model to attain a working framework that can be used to calculate the initial conditions in heavy ion collisions.

Post-Newtonian celestial dynamics is a relativistic theory of motion of massive bodies and test particles under the influence of relatively weak gravitational forces. The standard approach for development of this theory relies upon the key concept of the isolated astronomical system supplemented by the assumption that the background spacetime is flat. The standard post-Newtonian theory of motion was instrumental in the explanation of the existing experimental data on binary pulsars, satellite, and lunar laser ranging, and in building precise ephemerides of planets in the Solar System. Recent studies of the formation of large-scale structures in our Universe indicate that the standard post-Newtonian mechanics fails to describe more subtle dynamical effects in motion of the bodies comprising the astronomical systems of larger size—galaxies and clusters of galaxies—where the Riemann curvature of the expanding Friedmann-Lemaître-Robertson-Walker universe interacts with the local gravitational field of the astronomical system and, as such, cannot be ignored. The present paper outlines theoretical principles of the post-Newtonian mechanics in the expanding Universe. It is based upon the gauge-invariant theory of the Lagrangian perturbations of cosmological manifold caused by an isolated astronomical $N$-body system (the Solar System, a binary star, a galaxy, and a cluster of galaxies). We postulate that the geometric properties of the background manifold are described by a homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker metric governed by two primary components—the dark matter and the dark energy. The dark matter is treated as an ideal fluid with the Lagrangian taken in the form of pressure along with the scalar Clebsch potential as a dynamic variable. The dark energy is associated with a single scalar field with a potential which is hold unspecified as long as the theory permits. Both the Lagrangians of the dark matter and the scalar field are formulated in terms of the field variables which play a role of generalized coordinates in the Lagrangian formalism. It allows us to implement the powerful methods of variational calculus to derive the gauge-invariant field equations of the post-Newtonian celestial mechanics of an isolated astronomical system in an expanding universe. These equations generalize the field equations of the post-Newtonian theory in asymptotically flat spacetime by taking into account the cosmological effects explicitly and in a self-consistent manner without assuming the principle of liner superposition of the fields or a vacuole model of the isolated system, etc. The field equations for matter dynamic variables and gravitational field perturbations are coupled in the most general case of an arbitrary equation of state of matter of the background universe. We introduce a new cosmological gauge which generalizes the de Donder (harmonic) gauge of the post-Newtonian theory in asymptotically flat spacetime. This gauge significantly simplifies the gravitational field equations and allows one to find out the approximations where the field equations can be fully decoupled and solved analytically. The residual gauge freedom is explored and the residual gauge transformations are formulated in the form of the wave equations for the gauge functions. We demonstrate how the cosmological effects interfere with the local system and affect the local distribution of matter of the isolated system and its orbital dynamics. Finally, we worked out the precise mathematical definition of the Newtonian limit for an isolated system residing on the cosmological manifold. The results of the present paper can be useful in the Solar System for calculating more precise ephemerides of the Solar System bodies on extremely long time intervals, in galactic astronomy to study the dynamics of clusters of galaxies, and in gravitational wave astronomy for discussing the impact of cosmology on generation and propagation of gravitational waves emitted by coalescing binaries and/or merging galactic nuclei.

It has been shown that a nearly extremal black hole can be overcharged or overspun by a test particle if radiative and self-force effects are neglected, indicating that the cosmic censorship might fail. In contrast, the existing evidence in literature suggests that an extremal black hole cannot be overcharged or overspun in a similar process. In this paper, we show explicitly that even an exactly extremal black hole can be destroyed by a test particle, leading to a possible violation of the cosmic censorship. By considering higher-order terms, which were neglected in previous analysis, we show that the violation is generic for any extremal Kerr-Newman black hole with nonvanishing charge and angular momentum. We also find that the allowed parameter range for the particle is very narrow, indicating that radiative and self-force effects should be considered and may prevent violation of the cosmic censorship.

By making use of the background field method, the one-loop quantization for Euclidean Einstein-Weyl quadratic gravity model on the de Sitter universe is investigated. Using generalized zeta function regularization, the on-shell and off-shell one-loop effective actions are explicitly obtained, and one-loop renormalizability, as well as the corresponding one-loop renormalization group equations, is discussed. The so-called critical gravity is also considered.