We report an updated measurement of the $CP$-violating phase, ${\varphi }_s^{J/\psi \varphi }$, and the decay-width difference for the two mass eigenstates, $\Delta {\Gamma }_s$, from the flavor-tagged decay $B_s^0\to J/\psi \varphi$. The data sample corresponds to an integrated luminosity of $8.0{\mathrm{fb}}^{-1}$ accumulated with the D0 detector using $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ produced at the Fermilab Tevatron collider. The 68% Bayesian credibility intervals, including systematic uncertainties, are $\Delta {\Gamma }_s={0.163}_{-0.064}^{+0.065}{\mathrm{ps}}^{-1}$ and ${\varphi }_s^{J/\psi \varphi }=-{0.55}_{-0.36}^{+0.38}$. The $p$-value for the Standard Model point is 29.8%.

We present a search for neutral Higgs bosons $\varphi$ decaying into $b\overline{b}$, produced in association with $b$ quarks in $p\overline{p}$ collisions. This process could be observable in supersymmetric models with high values of $\tan \beta$. The event sample corresponds to $2.6{\mathrm{fb}}^{-1}$ of integrated luminosity collected with the CDF II detector at the Fermilab Tevatron collider. We search for an enhancement in the mass of the two leading jets in events with three jets identified as coming from $b$ quarks using a displaced vertex algorithm. A data-driven procedure is used to estimate the dijet mass spectrum of the nonresonant multijet background. The contributions of backgrounds and a possible Higgs boson signal are determined by a two-dimensional fit of the data, using the dijet mass together with an additional variable which is sensitive to the flavor composition of the three tagged jets. We set mass-dependent limits on $\sigma (p\overline{p}\to \varphi b)\times \mathcal{B}(\varphi \to b\overline{b})$ which are applicable for a narrow scalar particle $\varphi$ produced in association with $b$ quarks. We also set limits on $\tan \beta$ in supersymmetric Higgs models including the effects of the Higgs boson width.

We report a measurement of muon-neutrino disappearance in the T2K experiment. The 295-km muon-neutrino beam from Tokai to Kamioka is the first implementation of the off-axis technique in a long-baseline neutrino oscillation experiment. With data corresponding to $1.43\times {10}^{20}$ protons on target, we observe 31 fully-contained single $\mu$-like ring events in Super-Kamiokande, compared with an expectation of $104\pm 14(\mathrm{syst})$ events without neutrino oscillations. The best-fit point for two-flavor ${\nu }_{\mu }\to {\nu }_{\tau }$ oscillations is ${sin}^2(2{\theta }_{23})=0.98$ and $|\Delta m_{32}^2|=2.65\times {10}^{-3}{\mathrm{eV}}^2$. The boundary of the 90% confidence region includes the points $({sin}^2(2{\theta }_{23}),|\Delta m_{32}^2|)=(1.0,3.1\times {10}^{-3}{\mathrm{eV}}^2)$, (0.84, $2.65\times {10}^{-3}{\mathrm{eV}}^2$) and (1.0, $2.2\times {10}^{-3}{\mathrm{eV}}^2$).

We show how to derive several families of accelerating universe solutions to an Einstein-Aether gravity theory. These solutions provide possible descriptions of inflationary behavior in the early universe and late-time cosmological acceleration.

Recently we have constructed the conformal gravity with metric and torsion, finding the gravitational field equations that give the conservation laws and trace condition; in the present paper we apply this theory to the case of ELKO matter field, proving that their spin and energy densities once the matter field equations are considered imply the validity of the conservation laws and trace condition mentioned above.

Contrary to a widespread belief, measures of velocity can yield a value larger than $c$, the instantaneous light speed in vacuum, without contradicting Einstein’s relativity. Nevertheless, the effect turns out to be too small to explain the recently claimed superluminal velocity by the OPERA Collaboration. Several other general relativistic effects acting on the OPERA neutrinos are also analyzed. All of them are unable to explain the OPERA result.

We examine how the $(2+1)$-dimensional anti-de Sitter space is covered by the Fefferman-Graham system of coordinates for Minkowski, Rindler, and static de Sitter boundary metrics. We show that, in the last two cases, the coordinates do not cover the full anti-de Sitter space. On a constant-time slice, the line delimiting the excluded region has endpoints at the locations of the horizons of the boundary metric. Its length, after an appropriate regularization, reproduces the entropy of the dual conformal field theory on the boundary background. The horizon can be interpreted as the holographic image of the line segment delimiting the excluded region in the vicinity of the boundary.

We consider the Casimir interaction between two spheres at zero and finite temperature, for both scalar fields and electromagnetic fields. Of particular interest are the asymptotic expansions of the Casimir free energy when the distance between the spheres is small. The scenario where one sphere is inside the other is discussed in detail. At zero temperature, we compute analytically the leading and the next-to-leading order terms from the functional determinant representation of the Casimir energy. As expected, the leading order term agrees with the proximity force approximation. The results for the next-to-leading order terms are new. In the limit where the radius of the outer sphere goes to infinity, the results for the sphere-plane geometry are reproduced. At finite temperature, the leading order term is computed and it is found to agree completely with the proximity force approximation in the medium and high temperature regions. For the scenario where two spheres are outside each other, analogous results are obtained. In particular, when a Dirichlet, Neumann, or perfectly conducting boundary condition is imposed on both spheres, the next-to-leading order term of the zero temperature Casimir energy is found to agree with that computed recently using derivative expansion.

Certain momentum-dependent terms in the fermion sector of the Lorentz-violating standard model extension (SME) yield solvable classical Lagrangians of a type not mentioned in the literature. These cases yield new relatively simple examples of Finsler and pseudo-Finsler structures. One of the cases involves antisymmetric $d$-type terms and yields a new example of a relatively simple covariant Lagrangian.

In this paper we study the Breit-Wigner enhancement of dark matter (DM) annihilation considering the kinetic decoupling in the evolution of DM freeze-out at the early Universe. Since the DM temperature decreases much faster (as $1/R^2$) after kinetic decoupling than that in kinetic equilibrium (as $1/R$), we find the Breit-Wigner enhancement of the DM annihilation rate after the kinetic decoupling will affect the DM relic density significantly. Focusing on the model parameters that try to explain the anomalous cosmic positron/electron excesses observed by PAMELA/Fermi/ATIC, we find the elastic scattering $Xf\to Xf$ is not efficient in keeping dark matter in kinetic equilibrium, and the kinetic decoupling temperature $T_{\mathrm{kd}}$ is comparable to the chemical decoupling temperature $T_f\sim O(10)\mathrm{GeV}$. The reduction of the relic density after $T_{\mathrm{kd}}$ is significant and leads to a limited enhancement factor $\sim O({10}^2)$. Therefore, it is difficult to explain the anomalous positron/electron excesses in cosmic rays by DM annihilation and give the correct DM relic density simultaneously in the minimal Breit-Wigner enhancement model. We also mention that if the nonthermal DM velocity distribution after kinetic decoupling or new scattering processes are considered, this constraint could be changed.

With a method in which the Friedmann equation is written in a form such that evolution of the scale factor can be treated as that of a particle in a potential, we classify all possible cosmic evolutions in the DGP braneworld scenario with the dark radiation term retained. By assuming that the energy component is pressureless matter, radiation or vacuum energy, respectively, we find that in the matter or vacuum energy dominated case, the scale factor has a minimum value $a_0$. In the matter dominated case, the big bang singularity can be avoided in some special circumstances, and there may exist an oscillating universe or a bouncing one. If the cosmic scale factor is in the oscillating region initially, the universe may undergo an oscillation. After a number of oscillations, it may evolve to the bounce point through quantum tunneling and then expand. However, if the universe contracts initially from an infinite scale, it can turn around and then expand forever. In the vacuum energy dominated case, there exists a stable Einstein static state to avoid the big bang singularity. However, in certain circumstances in the matter or vacuum energy dominated case, a new kind of singularity may occur at $a_0$ as a result of the discontinuity of the scale factor. In the radiation dominated case, the universe may originate from the big bang singularity, but a bouncing universe which avoids this singularity is also possible.

We perform a cosmographic analysis using several cosmological observables such as the luminosity distance moduli, the volume distance, the angular diameter distance and the Hubble parameter. These quantities are determined using different data sets: supernovae type Ia and gamma ray bursts, the baryonic acoustic oscillations, the cosmic microwave background power spectrum and the Hubble parameter as measured from surveys of galaxies. This data set allows us to put constraints on the cosmographic expansion with unprecedented precision. We also present forecasts for the coefficients of the kinematic expansion using future but realistic data sets: constraints on the coefficients of the expansions are likely to improve by a factor of 10 with the upcoming large scale structure probes. Finally, we derive the set of the cosmographic parameters for several cosmological models (including $\Lambda \mathrm{CDM}$) and compare them with our best fit set. While distance measurements are unable to discriminate among these models, we show that the inclusion of the Hubble data set leads to strong constraints on the lowest order coefficients and, in particular, it is incompatible with $\Lambda \mathrm{CDM}$ at 3-$\sigma$ confidence level. We discuss the reliability of this determination and suggest further observations which might be of crucial importance for the viability of cosmographic tests in the future.

We present a simple and efficient method to compute the superhorizon evolution of the spectral index in multifield inflationary models, using transport equation techniques. We illustrate the evolution of $n_s$ with time for various interesting potentials.

We explore effects of the light vector $U$ boson, which is weakly coupled to nucleons, on the transition density ${\rho }_t$ and pressure $P_t$ at the inner edge separating the liquid core from the solid crust of neutron stars. Three methods, i.e., the thermodynamical approach, the curvature matrix approach, and the Vlasov equation approach, are used to determine the transition density ${\rho }_t$ with the Skyrme effective nucleon-nucleon interactions. We find that the ${\rho }_t$ and $P_t$ depend on not only the ratio of coupling strength to mass squared of the $U$ boson $g^2/{\mu }^2$ but also its mass $\mu$ due to the finite-range interaction from the $U$-boson exchange. In particular, our results indicate that the ${\rho }_t$ and $P_t$ are sensitive to both $g^2/{\mu }^2$ and $\mu$ if the $U$-boson mass $\mu$ is larger than about 2 MeV. Furthermore, we show that both $g^2/{\mu }^2$ and $\mu$ can have significant influence on the mass-radius relation and the crustal fraction of total moment of inertia of neutron stars. In addition, we study the exchange term contribution of the $U$ boson based on the density matrix expansion method, and demonstrate that the exchange term effects on the nuclear matter equation of state as well as the ${\rho }_t$ and $P_t$ are generally negligible.

Centaurus A (Cen A) is the nearest radio-loud AGN and is detected from radio to very high-energy gamma rays. Its nuclear spectral energy distribution (SED) shows a double-peak feature, which is well explained by the leptonic $\mathrm{\text{synchrotron}}+\mathrm{\text{synchrotron}}$ self-Compton model. This model however cannot account for the observed high energy photons in the TeV range, which display a distinct component. Here, we show that $\sim \mathrm{TeV}$ photons can be well interpreted as the ${\pi }^0$ decay products from $p\gamma$ interactions of Fermi-accelerated high-energy protons in the jet with the seed photons around the second SED peak at $\sim 170\mathrm{keV}$. Extrapolating the inferred proton spectrum to high energies, we find that this same model is consistent with the detection of two ultra-high-energy cosmic ray events detected by Pierre Auger Observatory from the direction of Cen A. We also estimate the GeV neutrino flux from the same process, and find that it is too faint to be detected by current high-energy neutrino detectors.

In inflationary models where the source of scalar perturbations is not the inflaton, but one or more scalars with negligible coupling with the inflaton, the resulting perturbations are not only scale invariant, but fully conformally invariant with conformal dimension close to zero. This is closely related to the fact that correlation functions can only depend on the de Sitter-invariant distances. These properties follow from the isometries of the inflationary de Sitter space and are thus completely independent of the dynamics. The 3-point function is fixed in terms of two constants, while the 4-point function is a function of two parameters (instead of five as in the absence of conformal invariance). The conformal invariance of correlators can be directly checked in Fourier space, as we show in an explicit example. A detection of a nonconformal correlation function, for example, an equilateral 3-point function, would imply that the source of perturbations is not decoupled from the inflaton.

Recent experimental results in direct dark matter detection may be interpreted in terms of a dark matter particle of mass around $10\mathrm{GeV}/c^2$. We show that the required scenario can be realized with a new dark matter particle charged under an extra Abelian gauge boson $Z^{\prime }$ that couples to quarks but not leptons. This is possible provided the $Z^{\prime }$ gauge boson is very light, around $10–20\mathrm{GeV}/c^2$ in mass, and the gauge coupling constant is small, ${\alpha }^{\prime }\sim {10}^{-5}$. Such scenarios are not constrained by accelerator data.

We investigate the prospects for the discovery of a neutral Higgs boson produced in association with a $b$ quark, followed by the Higgs decay into a pair of bottom quarks, $pp\to b{\varphi }^0\to bb\overline{b}+X$, at the CERN Large Hadron Collider (LHC) within the framework of unified supersymmetric models. The Higgs boson ${\varphi }^0$ can be a heavy scalar $H^0$ or a pseudoscalar $A^0$. Furthermore, this direct discovery channel is compared with the indirect Higgs searches in the rare decay $B_s\to {\mu }^{+}{\mu }^{-}$ at hadron colliders. Promising results are found for the minimal supergravity model, the anomaly-mediated supersymmetry breaking model, and the gauge-mediated supersymmetry breaking model. We find that the indirect search for $B(B_s\to {\mu }^{+}{\mu }^{-})\ge 5\times {10}^{-9}$ is complementary to the direct search for $b{\varphi }^0\to bb\overline{b}$ with $\sqrt{s}=14\mathrm{TeV}$ and an integrated luminosity ($L$) of $300{\mathrm{fb}}^{-1}$. In the anomaly-mediated supersymmetry breaking and gauge-mediated supersymmetry breaking models, $b{\varphi }^0\to bb\overline{b}$ with $L=300{\mathrm{fb}}^{-1}$ covers a larger area in the parameter space than $B(B_s\to {\mu }^{+}{\mu }^{-})\ge 5\times {10}^{-9}$. In addition, we present constraints from $b\to s\gamma$ and muon anomalous dipole moment ($\Delta a_{\mu }$) on the parameter space.

LHC has reported tantalizing hints for a Higgs boson of mass 125 GeV decaying into two photons. We focus on two-Higgs-doublet Models, and study the interesting possibility that the heavier scalar $H$ has been seen, with the lightest scalar $h$ having thus far escaped detection. Nonobservation of $h$ at LEP severely constrains the parameter-space of two-Higgs-doublet models. We analyze cases where the decay $H\to hh$ is kinematically allowed, and cases where it is not, in the context of type I, type II, lepton-specific, and flipped models.

The spectrum of emitted gluons from the process $\mathrm{g}+\mathrm{g}\to \mathrm{g}+\mathrm{g}+\mathrm{g}$ has been evaluated by relaxing some of the approximations used in earlier works. The differences in the results from earlier calculations have been pointed out. The formula obtained in the present work has been applied to estimate physical quantities like equilibration rate of gluons and the energy loss of fast gluon in the gluonic plasma.