We derive the Regge behavior for the forward scattering amplitude in scalar field theory using the method of regions. We find that the leading Regge behavior to all orders can be obtained. Regge physics emerges from a kinematic region that involves the overlap of several modes, so that a careful treatment of the overlap regions is important. The most consistent and efficient approach utilizes graphs containing collinear, anticollinear and Glauber modes, or modes of soft collinear effective theory with Glauber gluons (${\mathrm{SCET}}_{\mathrm{G}}$).

A feasibility study is presented for the search of the lightest top squark ($\tilde{t}$) in a compressed scenario, where its mass is approximately equal to the sum of the masses of the top quark and the lightest neutralino ${\tilde{\chi }}_1^0$ and there exists no limit from the current 8 TeV data or from the 14 TeV projections. The study is performed in the final state of two $b$ jets, one lepton, large missing transverse energy, and two energetic jets with a large separation in pseudorapidity, in opposite hemispheres, and with large dijet mass. The analysis shows that the LHC could probe compressed top-squark masses $\sim 300\mathrm{GeV}$ with an integrated luminosity of $300{\mathrm{fb}}^{-1}$ for two- ($t+{\tilde{\chi }}_1^0$) and three-body ($b+W+{\tilde{\chi }}_1^0$) final states arising from the top-squark decay at $5\sigma$ significance with no systematic uncertainty. After including the systematics, the significance for $m_{\tilde{t}}=200\mathrm{GeV}$ and $\mathrm{\Delta }M=7\mathrm{GeV}$ is expected to be $6(3)\sigma$ for $300{\mathrm{fb}}^{-1}$ luminosity with 3(5)% systematic uncertainty, while the significance becomes $4(2)\sigma$ for the same top-squark mass with $\mathrm{\Delta }M=-7\mathrm{GeV}$.

In the minimal supersymmetric standard model (MSSM) the lightest superpartner of the left-handed neutrinos is ruled out as a candidate for dark matter because of its large elastic cross section with the nucleus mediated via the $Z$ boson. We resurrect this candidate by extending the MSSM with two triplets with opposite hypercharge. The addition of the triplets not only plays the role of generating small Majorana masses for the left-handed active neutrinos, but it also makes the lightest sneutrino a viable candidate for dark matter. We then discuss the relevant parameter space that can give rise to the right amount of (thermal) relic abundance as well as satisfy the current direct-detection constraints from XENON100 and LUX. We find that sneutrino dark matter with mass 370–550 GeV can give rise to the correct thermal relic abundance while coannihilating with the bino-like neutralino.

We study the possibility of generating nonzero reactor mixing angle ${\theta }_{13}$ by perturbing the $\mu -\tau$ symmetric neutrino mass matrix. The leading-order $\mu -\tau$ symmetric neutrino mass matrix originates from a type I seesaw mechanism, whereas the perturbations to $\mu -\tau$ symmetry originate from a type II seesaw term. We consider four different realizations of $\mu -\tau$ symmetry, bimaximal mixing, tribimaximal mixing, hexagonal mixing, and golden ratio mixing, all giving rise to ${\theta }_{13}=0,{\theta }_{23}=\frac{\pi }{4}$ but different nonzero values of solar mixing angle ${\theta }_{12}$. We assume a minimal $\mu -\tau$ symmetry breaking type II seesaw mass matrix as a perturbation and calculate the neutrino oscillation parameters as a function of type II seesaw strength. We then consider the origin of nontrivial leptonic $CP$ phase in the charged lepton sector and calculate the lepton asymmetry arising from the lightest right-handed neutrino decay by incorporating the presence of both type I and type II seesaws. We constrain the type II seesaw strength as well as the leptonic $CP$ phase (and hence the charged lepton sector) by comparing our results with experimental neutrino oscillation parameters as well as the Planck bound on the baryon-to-photon ratio. Finally, we extend our analysis on lepton flavor violating decays like $\mu \to e\gamma$ and $\mu \to eee$ due to the exchange of a TeV scale Higgs triplet scalar within the low scale type II seesaw framework. The branching ratios for these lepton flavor processes are examined with the small type II perturbation term $\omega$, and the estimated values are very close to the experimental bound coming from current search experiments.

Searches for supersymmetry (SUSY) are presented based on the electroweak pair production of neutralinos and charginos, leading to decay channels with Higgs, $Z$, and $W$ bosons and undetected lightest SUSY particles (LSPs). The data sample corresponds to an integrated luminosity of about $19.5{\mathrm{fb}}^{-1}$ of proton-proton collisions at a center-of-mass energy of 8 TeV collected in 2012 with the CMS detector at the LHC. The main emphasis is neutralino pair production in which each neutralino decays either to a Higgs boson ($h$) and an LSP or to a $Z$ boson and an LSP, leading to $hh$, $hZ$, and $ZZ$ states with missing transverse energy ($E_{\mathrm{T}}^{\text{miss}}$). A second aspect is chargino-neutralino pair production, leading to $hW$ states with $E_{\mathrm{T}}^{\text{miss}}$. The decays of a Higgs boson to a bottom-quark pair, to a photon pair, and to final states with leptons are considered in conjunction with hadronic and leptonic decay modes of the $Z$ and $W$ bosons. No evidence is found for supersymmetric particles, and 95% confidence level upper limits are evaluated for the respective pair production cross sections and for neutralino and chargino mass values.

One of the major motivations to search for a dark gauge boson of MeV–GeV scale is the long-standing $g_{\mu }-2$ anomaly. Because of active searches such as fixed target experiments and rare meson decays, the $g_{\mu }-2$ favored parameter region has been rapidly reduced. With the most recent data, it is practically excluded now in the popular dark photon model. We overview the issue and investigate a potentially alternative model based on the gauged lepton number or $U(1{)}_L$. The $g_{\mu }-2$ favored parameter region of the $U(1{)}_L$ survives all the constraints that were critical in the dark photon case, yet it is disfavored by the new constraints from the large flux neutrino experiments.

A system of relativistic Snyder particles with mutual two-body interaction that lives in a noncommutative Snyder geometry is studied. The underlying novel symplectic structure is a coupled and extended version of (single-particle) Snyder algebra. In a recent work by Casalbuoni and Gomis [Phys. Rev. D 90, 026001 (2014)], a system of interacting conventional particles (in commutative spacetime) was studied with special emphasis on its conformal invariance. Proceeding along the same lines, we have shown that our interacting Snyder particle model is also conformally invariant. Moreover, the conformal Killing vectors have been constructed. Our main emphasis is on the Hamiltonian analysis of the conformal symmetry generators. We demonstrate that the Lorentz algebra remains undeformed, but validity of the full conformal algebra requires further restrictions.

Chern-Simons (CS) $\theta$-systems are described by a $\theta \int F\wedge F$ term in the action ($\theta$ is an adimensional parameter), which does not change field equations in the bulk, but affects the system behavior when it is bounded. When two of those $\theta$-systems, each one characterized by a different value of $\theta$ (even zero), share a common boundary, surface effects are then induced by a CS $\theta$ term. Here, we study the consequences of the above in the propagation of electromagnetic radiation in $\theta$-systems. In a previous paper, electromagnetic radiation properties traversing a $\theta$-vacuum were analyzed, where a number of interesting features arise related to polarization and energy distribution. Now, we investigate how electric and magnetic properties of the $\theta$-system affect the optical response. Apart from the well-known Kerr polarization rotation found for the particular case of topological insulators, we examine in detail the issue, and the results could be applied in other contexts where the $\theta$ term accounts for the system dynamics. In particular, we find two different Brewster angles, for $s$ and $p$ polarization of reflected radiation, respectively, with peculiar features derived from the $\theta$ term influence. Possible applications of these results are discussed.

We have established the Gupta-Bleuler quantization of the photon belonging to the anisotropic parity-even sector of the $CPT$-even and Lorentz-violating (LV) nonbirefringent electrodynamics of the standard model extension. We first present a rule for the Maxwell electrodynamics to be successfully quantized via the Gupta-Bleuler technique in the Lorentz gauge. Recognizing the failure of the Gupta-Bleuler method in the Lorentz gauge, ${\partial }_{\mu }{A}^{\mu }=0$, for this massless LV theory, we argue that Gupta-Bleuler can be satisfactorily implemented by choosing a modified Lorentz condition, ${\partial }_{\mu }{A}^{\mu }+{\kappa }^{\mu \nu }{\partial }_{\mu }{A}_{\nu }=0$, where ${\kappa }^{\mu \nu }$ represents the Lorentz violation in the photon sector. By using a plane-wave expansion for the gauge field, whose polarization vectors are determined by solving an eigenvalue problem, and a weak Gupta-Bleuler condition, we obtain a positive-energy Hamiltonian in terms of annihilation and creation operators. The field commutation relation is written in terms of modified Pauli-Jordan functions, revealing the preservation of microcausality for sufficiently small LV parameters. This procedure works even at second order (the birefringent regime).

Some extensions beyond the Standard Model propose the existence of nearly degenerate heavy sterile neutrinos. If kinematically allowed these can be resonantly produced and decay in a cascade to common final states. The common decay channels lead to mixing of the heavy sterile neutrino states and interference effects. We implement nonperturbative methods to study the dynamics of the cascade decay to common final states, which features similarities but also noteworthy differences with the case of neutral meson mixing. We show that mixing and oscillations among the nearly degenerate sterile neutrinos can be detected as quantum beats in the distribution of final states produced from their decay. These oscillations would be a telltale signal of mixing between heavy sterile neutrinos. We study in detail the case of two nearly degenerate sterile neutrinos produced in the decay of pseudoscalar mesons and decaying into a purely leptonic “visible” channel: ${\nu }_h\to e^{+}{e}^{-}{\nu }_a$. Possible cosmological implications for the effective number of neutrinos $N_{\text{eff}}$ are discussed.

We present an algorithm for calculating the metric perturbations and gravitational self-force for extreme-mass-ratio inspirals (EMRIs) with eccentric orbits. The massive black hole is taken to be Schwarzschild, and metric perturbations are computed in Lorenz gauge. The perturbation equations are solved as coupled systems of ordinary differential equations in the frequency domain. Accurate local behavior of the metric is attained through use of the method of extended homogeneous solutions, and mode-sum regularization is used to find the self-force. We focus on calculating the self-force with sufficient accuracy to ensure its error contributions to the phase in a long-term orbital evolution will be $\delta \mathrm{\Phi }\lesssim 10^{-2}\mathrm{rad}$. This requires the orbit-averaged force to have fractional errors $\lesssim 10^{-8}$ and the oscillatory part of the self-force to have errors $\lesssim 10^{-3}$ (a level frequently easily exceeded). Our code meets this error requirement in the oscillatory part, extending the reach to EMRIs with eccentricities of $e\lesssim 0.8$, if augmented by use of fluxes for the orbit-averaged force, or to eccentricities of $e\lesssim 0.5$ when used as a stand-alone code. Further, we demonstrate accurate calculations up to orbital separations of $a\simeq 100M$, beyond that required for EMRI models and useful for comparison with post-Newtonian theory. Our principal developments include (1) use of fully constrained field equations, (2) discovery of analytic solutions for even-parity static modes, (3) finding a preconditioning technique for outer homogeneous solutions, (4) adaptive use of quad precision, (5) jump conditions to handle near-static modes, and (6) a hybrid scheme for high eccentricities.

We report results from simulations in general relativity of magnetized disks accreting onto merging black hole binaries, starting from relaxed disk initial data. The simulations feature an effective, rapid radiative cooling scheme as a limiting case of future treatments with radiative transfer. Here we evolve the systems after binary-disk decoupling through inspiral and merger, and analyze the dependence on the binary mass ratio with $q\equiv m_{\text{bh}}/M_{\mathrm{BH}}=1,1/2$, and $1/4$. We find that the luminosity associated with local cooling is larger than the luminosity associated with matter kinetic outflows, while the electromagnetic (Poynting) luminosity associated with bulk transport of magnetic field energy is the smallest. The cooling luminosity around merger is only marginally smaller than that of a single, nonspinning black hole. Incipient jets are launched independently of the mass ratio, while the same initial disk accreting on a single nonspinning black hole does not lead to a jet, as expected. For all mass ratios we see a transient behavior in the collimated, magnetized outflows lasting 2–5 $(M/10^8{M}_{\odot })$ days after merger: the outflows become increasingly magnetically dominated and accelerated to higher velocities, boosting the Poynting luminosity. These sudden changes can alter the electromagnetic emission across the jet and potentially help distinguish mergers of black holes in active galactic nucleus (AGNs) from single accreting black holes based on jet morphology alone.

Gravitational wave background results from the superposition of gravitational waves generated from all sources across the Universe. Previous efforts on detecting such a background with pulsar timing arrays assume it is an isotropic Gaussian background with a power law spectrum. However, when the number of sources is limited, the background might be nonGaussian or the spectrum might not be a power law. Correspondingly, previous analysis may not work effectively. Here, we use a method—Bayesian nonparametric analysis—to try to detect a generic gravitational wave background, which directly sets constraints on the feasible shapes of the pulsar timing signals induced by a gravitational wave background and allows more flexible forms of the background. Our Bayesian nonparametric analysis will infer if a gravitational wave background is present in the data, and also estimate the parameters that characterize the background. This method will be much more effective than the conventional one assuming the background spectrum follows a power law in general cases. While the context of our discussion focuses on pulsar timing arrays, the analysis itself is directly applicable to detect and characterize any signals that arise from the superposition of a large number of astrophysical events.

We describe several new techniques which accelerate Bayesian searches for continuous gravitational-wave emission from supermassive black-hole binaries using pulsar-timing arrays. These techniques mitigate the problematic increase of search dimensionality with the size of the pulsar array which arises from having to include an extra parameter per pulsar as the array is expanded. This extra parameter corresponds to searching over the phase of the gravitational wave as it propagates past each pulsar so that we can coherently include the pulsar term in our search strategies. Our techniques make the analysis tractable with powerful evidence-evaluation packages like MultiNest. We find good agreement of our techniques with the parameter-estimation and Bayes factor evaluation performed with full signal templates and conclude that these techniques make excellent first-cut tools for detection and characterization of continuous gravitational-wave signals with pulsar-timing arrays. Crucially, at low to moderate signal-to-noise ratios the factor by which the analysis is sped up can be $\gtrsim 100$, permitting rigorous programs of systematic injection and recovery of signals to establish robust detection criteria within a Bayesian formalism.

The general two-Higgs doublet model (2HDM) contains a rich spectrum of neutral and charged Higgs bosons, whose detection would be a clear signal of new physics. When the Higgs potential is $CP$ conserving, the spectrum includes a pseudoscalar mass eigenstate $A^0$, which does not couple to vector bosons at tree level. However, fermionic loops (top and bottom mainly) induce the coupling $AV{V}^{\prime }$ (with $V,V^{\prime }=\gamma ,Z$) at higher orders. We evaluate the amplitude for the decays $A^0\to ZZ,Z\gamma ,\gamma \gamma$, including a generic fermionic loop contribution, and present results on the branching ratios for 2HDM-I,II and III. Current LHC searches on heavy Higgs bosons are used as an estimate to constrain the allowed mass range for $A^0$.

Time-dependent $CP$ asymmetry measurements in $D\to h^{+}{h}^{-}$ decays, where $h=\pi$ or $\rho$ can, in principal, be used to constrain the angle ${\beta }_c$ of the $cu$ unitarity triangle up to theoretical uncertainties. Here we discuss the theoretical uncertainty from penguin contributions that can be investigated through the use of isospin analyses. We show that uncertainty from penguin pollution on a measurement of ${\beta }_c$ (or alternatively the mixing phase) in $D^0\to {\pi }^{+}{\pi }^{-}$ (${\rho }^{+}{\rho }^{-}$) decays is 2.7° (4.6°). We also comment on the applicability of this method to $D^0\to \rho \pi$ decays for which measurements of weak phases with a precision below the one degree level may be possible.

Here, we update our previous global fit of neutrino oscillations by including the recent results that have appeared since the Neutrino 2012 conference. These include the measurements of reactor antineutrino disappearance reported by Daya Bay and RENO, together with latest T2K and MINOS data including both disappearance and appearance channels. We also include the revised results from the third solar phase of Super-Kamiokande, SK-III, as well as new solar results from the fourth phase of Super-Kamiokande, SK-IV. We find that the preferred global determination of the atmospheric angle ${\theta }_{23}$ is consistent with maximal mixing. We also determine the impact of the new data upon all the other neutrino oscillation parameters with an emphasis on the increasing sensitivity to the $CP$ phase, thanks to the interplay between accelerator and reactor data. In the Appendix, we present the updated results obtained after the inclusion of new reactor data presented at the Neutrino 2014 conference. We discuss their impact on the global neutrino analysis.

We discuss the way in which field theory quantities assemble the spatial geometry of three-dimensional anti–de Sitter space (${\mathrm{AdS}}_3$). The field theory ingredients are the entanglement entropies of boundary intervals. A point in ${\mathrm{AdS}}_3$ corresponds to a collection of boundary intervals which is selected by a variational principle we discuss. Coordinates in ${\mathrm{AdS}}_3$ are integration constants of the resulting equation of motion. We propose a distance function for this collection of points, which obeys the triangle inequality as a consequence of the strong subadditivity of entropy. Our construction correctly reproduces the static slice of ${\mathrm{AdS}}_3$ and the Ryu-Takayanagi relation between geodesics and entanglement entropies. We discuss how these results extend to quotients of ${\mathrm{AdS}}_3$—the conical defect and the BTZ geometries. In these cases, the set of entanglement entropies must be supplemented by other field theory quantities, which can carry the information about lengths of nonminimal geodesics.

We undertake a complete and covariant treatment for the quadratic Lagrangian of all of the degrees of freedom of massive gravity with a fixed flat fiducial metric for arbitrary massive gravity parameters around any isotropic self-accelerating background solution. Generically, three out of four Stückelberg degrees of freedom propagate in addition to the usual two tensor degrees of freedom of general relativity. The complete kinetic structure typically is only revealed at an order in the graviton mass that is equivalent to retaining curvature terms in a locally flat expansion. These results resolve several apparent discrepancies in the literature where zero degrees of freedom propagate in either special cases or approximate treatments as well as decoupling limit analyses which attempt to count longitudinal degrees of freedom.

Whenever the condition of anomaly freedom is imposed within the framework of effective approaches to loop quantum cosmology, one seems to conclude that a deformation of general covariance is required. Here, starting from a general deformation we regain an effective gravitational Lagrangian including terms up to fourth order in extrinsic curvature. We subsequently constrain the form of the corrections for the homogeneous case, and then investigate the conditions for the occurrence of a big bounce and the realization of an inflationary era, in the presence of a perfect fluid or scalar field.