We consider constraints on simplified models in which scalar dark matter annihilates to light charged leptons through the exchange of charged mediators. We find that loop diagrams will contribute corrections to the magnetic and electric dipole moments of the light charged leptons, and experimental constraints on these corrections place significant bounds on the dark matter annihilation cross section. In particular, annihilation to electrons with an observable cross section would be ruled out, while annihilation to muons is only permitted if the dominant contributions arise from $CP$-violating interactions.

The pion mass dependence of the nucleon mass within the covariant $SU(2)$ baryon chiral perturbation theory both without and with explicit $\Delta (1232)$ degrees of freedom up to order $p^4$ is investigated. By fitting to a comprehensive set of lattice QCD data in 2 and $2+1$ flavors from several collaborations, for pion masses $M_{\pi }<420\mathrm{MeV}$, we obtain low energy constants of natural size that are compatible with pion-nucleon scattering data. Our results are consistent with the rather linear pion mass dependence showed by lattice QCD. In the 2 flavor case we have also performed simultaneous fits to nucleon mass and ${\sigma }_{\pi N}$ data. As a result of our analysis, which encompasses the study of finite volume corrections and discretization effects, we report a value of ${\sigma }_{\pi N}=41(5)(4)\mathrm{MeV}$ in the 2 flavor case and ${\sigma }_{\pi N}=52(3)(8)\mathrm{MeV}$ for $2+1$ flavors, where the inclusion of the $\Delta (1232)$ resonance changes the results by around 9 MeV. In the 2 flavor case we are able to set independently the scale for lattice QCD data, given by a Sommer scale of $r_0=0.493(23)\mathrm{fm}$.

We simulate SU(2) gauge theory at temperatures ranging from slightly below $T_c$ to roughly $2T_c$ for two different values of the gauge coupling. Using a histogram method, we extract the effective potential for the Polyakov loop and for the phases of the eigenvalues of the thermal Wilson loop, in both the fundamental and adjoint representations. We show that the classical potential of the fundamental loop can be parametrized within a simple model which includes a Vandermonde potential and terms linear and quadratic in the Polyakov loop. We discuss how parametrizations for the other cases can be obtained from this model.

We present a new functional form of pion and kaon fragmentation functions up to next-to-leading order obtained through a global fit to single-inclusive electron-positron annihilation data, and also employ the semi-inclusive deep inelastic scattering asymmetry data from HERMES and COMPASS to determine fragmentation functions. We also apply very recent electron-positron annihilation data from BABAR and Belle at $\sqrt{s}=10.54\mathrm{GeV}$ and $\sqrt{s}=10.52\mathrm{GeV}$, respectively. In this analysis we consider the impression of semi-inclusive deep inelastic scattering asymmetry data on the fragmentation functions, where the produced hadrons of different electric charge are identified. We break the symmetry assumption between the quark and antiquark fragmentation functions for favored partons by using the asymmetry data. The results of our analysis are in good agreement with electron-positron annihilation data and also with all the semi-inclusive deep inelastic scattering asymmetry data. We also apply the obtained fragmentation functions to predict the scaled-energy distribution of ${\pi }^{+}/K^{+}$ inclusively produced in top-quark decays at next-to-leading order using the zero-mass variable-flavor-number scheme, exploiting the universality and scaling violations of fragmentation functions.

Solar neutrino experiments have yet to see directly the transition region between matter-enhanced and vacuum oscillations. The transition region is particularly sensitive to models of nonstandard neutrino interactions and propagation. We examine several such nonstandard models, which predict a lower-energy transition region and a flatter survival probability for the ${}^8\mathrm{B}$ solar neutrinos than the standard large-mixing angle (LMA) model. We find that while some of the nonstandard models provide a better fit to the solar neutrino data set, the large measured value of ${\theta }_{13}$ and the size of the experimental uncertainties lead to a low statistical significance for these fits. We have also examined whether simple changes to the solar density profile can lead to a flatter ${}^8\mathrm{B}$ survival probability than the LMA prediction, but find that this is not the case for reasonable changes. We conclude that the data in this critical region are still too poor to determine whether any of these models, or the LMA model, is the best description of the data.

We report the first observation of ${\rm Y}(10860)\to {\rm Y}(1,2,3S){\pi }^0{\pi }^0$ decays. The neutral partner of the $Z_b^{\pm }(10610)$, the $Z_b^0(10610)$ decaying to ${\rm Y}(2,3S){\pi }^0$, is observed for the first time with a $6.5\sigma$ significance using a Dalitz analysis of ${\rm Y}(10860)\to {\rm Y}(2,3S){\pi }^0{\pi }^0$ decays. The results are obtained with a $121.4{\mathrm{fb}}^{-1}$ data sample collected with the Belle detector at the ${\rm Y}(10860)$ resonance at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider.

The thermodynamic equilibrium states of a static thin ring shell in a ($2+1$)-dimensional flat spacetime is analyzed. Inside the ring the spacetime is flat, whereas outside it is conical flat. The first law of thermodynamics applied to the thin shell leads to a shell’s entropy, which is a function of its mass alone. Two simple forms for this mass function are given leading to two different expressions for the entropy. The equations of thermodynamic stability are analyzed resulting in certain allowed regions for the free parameters. Contrary to the usual ($3+1$)-dimensional case, this shell’s entropy is purely classic, as the only fundamental constant that enters into the problem is the ($2+1$)-dimensional gravitational constant $G_3$, which has units of inverse mass.

We study the theory that contains two spin-2 fields. This theory can be regarded as a simplified version of higher spin gravity in ${\mathrm{AdS}}_3$. It can be formulated either in the first order formulation or in the second order formulation. From the first order formulation, we construct the black holes in the theory and study the thermodynamics of these black holes with the help of dual holographic operator product expansion. From the higher spin point of view, this black hole is most naturally regarded as a black hole with a spin-2 hair. In the second order formulation, we obtain an action for the metric and extra spin-2 fields and analyze the corresponding black holes. Even though for some simple cases, the conventional notions, such as the horizon, may help us to read part of the information of the black hole, they break down in generic cases. On the other hand, the action in the second order formulation could be rewritten in the form of a decoupled ${\mathrm{AdS}}_3$ bigravity. Moreover, the entropy of the black hole with the spin-2 hair could be reproduced from the ${\mathrm{AdS}}_3$ bigravity in the Euclidean path-integral formalism.

Factorization is possible due to the universal behavior of Yang-Mills theories in soft and collinear limits. Here, we take a small step towards a more transparent understanding of these limits by proving a form of perturbative factorization at tree level using on-shell spinor helicity methods. We present a concrete and self-contained expression of factorization in which matrix elements in QCD are related to products of other matrix elements in QCD up to leading order in a power-counting parameter determined by the momenta of certain physical on-shell states. Our approach uses only the scaling of momenta in soft and collinear limits, avoiding any assignment of scaling behavior to unphysical (and gauge-dependent) fields. The proof of factorization exploits many advantages of helicity spinors, such as the freedom to choose different reference vectors for polarizations in different collinear sectors. An advantage of this approach is that once factorization is shown to hold in QCD, the transition to soft-collinear effective theory is effortless.

We study consequences of Lorentz symmetry violation in a $z=2$ Lifshitz extension of QED in $3+1$ dimensions, and we discuss nontrivial effects of quantization. Because of the specific power of space momentum in propagators of the model, dimensional regularization leads to an unusual interpretation of loop integrals, which are finite even when the space dimension goes to the integer 3. We check the consistency of the approach by calculating the (vanishing) corrections to the photon mass and the IR-divergence-free corrections to the dispersion relation for massless fermions.

We analyze the behavior of the geodesic motion of test particles in the spacetime of a specific class of axially symmetric static vacuum solutions to the Einstein equations, hereafter referred to as the linearized multipole solution. We discuss its suitability to describe a quasispherical spacetime. The existence of an innermost stable circular orbit very close to the (singular) horizon of the source is established. The existence of such a stable orbit, closer than that of the Schwarzschild metric, as well as the appearance of a splitting in the admissible region of circular orbits, is shown to be due to the multipole structure of the solution, thereby providing additional potential observational evidence for distinguishing Schwarzschild black holes from naked singularities.

In this paper we investigate the global dynamics for the minimally coupled scalar field representation of the modified Chaplygin gas in the context of flat Friedmann-Lemaître-Robertson Walker cosmology. The tool for doing this is a new set of bounded variables that lead to a regular dynamical system. It is shown that the exact modified Chaplygin gas perfect fluid solution appears as a straight line in the associated phase plane. It is also shown that no other solutions stay close to this solution during their entire temporal evolution, but that there exists an open subset of solutions that stay arbitrarily close during an intermediate time interval, and into the future in the case when the scalar field potential exhibits a global minimum.

We start with formulation of the generalized Fermat’s principle for light propagation in a curved spacetime. We apply Pontryagin’s minimum principle of the optimal control theory and obtain an effective Hamiltonian for null geodesics in a curved spacetime. We explicitly demonstrate that dynamical equations for this Hamiltonian correctly reproduce null geodesic equations. Other forms of the action for light rays in a curved spacetime are also discussed.

We present a new manifestation of the nonlinearity of gravity-matter interactions. We show explicitly that there exists a nongravitating dynamical scalar field solution in Eddington-inspired Born-Infeld gravity. This kind of solution has not been found in previous literature based on general relativity or other modified gravity theories. The perturbation analysis shows that the solution is a late-time attractor if the scalar field rolls down the potential. This indicates that there are two weak-gravity regimes in the theory—one in the general relativity regime, and the other in the Eddington regime.

It is shown that any homogeneous and isotropic universe, independently of its spatial topology and matter content, allows for the presence of a conformal stealth, i.e., a nontrivial conformally invariant scalar field with vanishing energy-momentum tensor, which evolves along with the universe without causing even the smallest backreaction. Surprisingly, this gravitationally invisible universal witness is inhomogeneous with zero consequences for the underlying cosmology. Additionally, it is shown that these results are not exclusive of a four-dimensional universe by generalizing them to higher dimensions.

The cold dark matter at the center of a galaxy will be redistributed by the presence of a massive black hole. The redistribution may be determined using an approach pioneered by Gondolo and Silk: begin with a model distribution function for the dark matter, and “grow” the black hole adiabatically, holding the adiabatic invariants of the motion constant. Unlike the approach of Gondolo and Silk, which adopted Newtonian theory together with ad hoc correction factors to mimic general relativistic effects, we carry out the calculation fully relativistically, using the exact Schwarzschild geometry of the black hole. We find that the density of dark matter generically vanishes at $r=2R_{\mathrm{S}}$, not $4R_{\mathrm{S}}$ as found by Gondolo and Silk, where $R_{\mathrm{S}}$ is the Schwarzschild radius, and that the spike very close to the black hole reaches significantly higher densities. We apply the relativistic adiabatic growth framework to obtain the final dark-matter density for both cored and cusped initial distributions. Besides the implications of these results for indirect detection estimates, we show that the gravitational effects of such a dark-matter spike are significantly smaller than the relativistic effects of the black hole, including frame dragging and quadrupolar effects, for stars orbiting close to the black hole that might be candidates for testing the black-hole no-hair theorems.

Early indications from the LHC for the observed scalar boson imply properties close to the Standard Model Higgs, putting considerable constraints on TeV scale new physics scenarios. In this paper we consider flat extra dimensional scenarios with the fifth spatial dimension compactified on an $S^1/Z_2$ orbifold. We find in the minimal model the experimentally preferred effective Higgs couplings to gluons and photons at 95% confidence level disfavor the new physics scale below 1.3 TeV. We demonstrate that a generalization of these models to include brane localized kinetic terms can relieve the tension to accommodate scales as low as 0.4 TeV.

We study the possibility of family unification on the basis of $SU(N)$ gauge theory on the six-dimensional space-time, $M^4\times T^2/Z_N$. We obtain enormous numbers of models with three families of $SU(5)$ matter multiplets and those with three families of the standard model multiplets, from a single massless Dirac fermion with a higher-dimensional representation of $SU(N)$, through the orbifold breaking mechanism.

We study the decay modes of $B_s^0({\overline{B}}_s^0)\to D_s^{\pm }{K}^{\mp }$, $B_s^0({\overline{B}}_s^0)\to D^{\pm }{\pi }^{\mp }$, and $B^0({\overline{B}}^0)\to D^{\pm }{\pi }^{\mp }$ in the perturbative QCD approach based on $k_T$ factorization, including the branching ratios and $CP$ violation parameters which provide a clear way to extract the Cabibbo-Kobayashi-Maskawa angle $\gamma$. Our results of branching ratios of $B_s^0({\overline{B}}_s^0)\to D_s^{\pm }{K}^{\mp }$ and $B^0({\overline{B}}^0)\to D^{\pm }{\pi }^{\mp }$ and the $CP$ asymmetry of $B^0({\overline{B}}^0)\to D^{\pm }{\pi }^{\mp }$ agree well with the experimental data. We also give predictions of the other observables, which provide some guidance for experiments in the future, especially for the LHCb experiment.

Dynamics and direct $CP$ violation in three-body charmless decays of charged $B$ mesons to a proton, an antiproton and a light meson (pion or kaon) are studied using data, corresponding to an integrated luminosity of $1.0{\mathrm{fb}}^{-1}$, collected by the LHCb experiment in $pp$ collisions at a center-of-mass energy of 7 TeV. Production spectra are determined as a function of Dalitz-plot and helicity variables. The forward-backward asymmetry of the light meson in the $p\overline{p}$ rest frame is measured. No significant $CP$ asymmetry in $B^{+}\to p\overline{p}{K}^{+}$ decay is found in any region of the Dalitz plane. We present the first observation of the decay $B^{+}\to \overline{\Lambda }(1520)(\to K^{+}\overline{p})p$ near the $K^{+}\overline{p}$ threshold and measure $\mathcal{B}(B^{+}\to \overline{\Lambda }(1520)p)=({3.9}_{-0.9}^{+1.0}(\mathrm{stat})\pm 0.1(\mathrm{syst})\pm 0.3(\mathrm{BF}))\times {10}^{-7}$, where BF denotes the uncertainty on secondary branching fractions.