We calculate the yield of high-energy neutrinos produced in astrophysical sources with negligible magnetic fields varying their interaction depth from nearly transparent to opaque. We take into account the scattering of secondaries on background photons as well as the direct production of neutrinos in decays of charm mesons. If multiple scattering of nucleons becomes important, the neutrino spectra from meson and muon decays are strongly modified with respect to transparent sources. Characteristic for neutrino sources containing photons as scattering targets is a strong energy-dependence of the ratio $R^0$ of ${\nu }_{\mu }$ and ${\nu }_e$ fluxes at the sources, ranging from $R^0={\varphi }_{\mu }/{\varphi }_e\sim 0$ below threshold to $R^0\sim 4$ close to the energy where the decay length of charged pions and kaons equals their interaction length on target photons. Above this energy, the neutrino flux is strongly suppressed and depends mainly on charm production.

We consider proton-nucleus collisions at high energy in the color glass condensate framework, and extract from the gluon production cross section the probabilities of having a definite number of multiple scatterings in the nucleus. Various properties of the distribution of the number of multiple scatterings are studied, and we conclude that events in which the momentum of a hard jet is compensated by many much softer particles on the opposite side are very unlikely except for extreme values of the saturation momentum. In the same framework, we also investigate the possibility to estimate the impact parameter of a proton-nucleus collision, from the measure of the multiplicity of its final state.

We investigate the effect of a six fermion determinant interaction on color superconductivity as well as on chiral symmetry breaking. Coupled mass gap equations and the superconducting gap equation are derived through the minimization of the thermodynamic potential. The effect of nonzero quark-antiquark condensates on the superconducting gap is derived. This becomes particularly relevant for the case of 2-flavor superconducting matter with unpaired strange quarks in the diquark channel. While the effect of a six fermion interaction leads to an enhancement of $u\mathrm{\text{−}}d$ superconductivity, due to nonvanishing strange quark-antiquark condensates, such an enhancement will be absent at higher densities for $u\mathrm{\text{−}}s$ or $d\mathrm{\text{−}}s$ superconductivity due to early (almost) vanishing of light quark-antiquark condensates.

The leading- and higher-twist distribution amplitudes and light-cone wave functions of real and virtual photons are analyzed in chiral quark models. The calculations are performed in the nonlocal quark model based on the instanton picture of the QCD vacuum, as well as in the spectral quark model and the Nambu–Jona-Lasinio model with the Pauli-Villars regulator, which both treat interaction of quarks with external fields locally. We find that in all considered models the leading-twist distribution amplitudes of the real photon defined at the quark-model momentum scale are constant or remarkably close to the constant in the $x$ variable, thus are far from the asymptotic limit form. The QCD evolution to higher momentum scales is necessary and we carry it out at the leading order of the perturbative theory for the leading-twist amplitudes. We provide estimates for the magnetic susceptibility of the quark condensate ${\chi }_{\mathrm{m}}$ and the coupling $f_{3\gamma }$, which in the nonlocal model turn out to be close to the estimates from QCD sum rules. We find the higher-twist distribution amplitudes at the quark model scale and compare them to the Wandzura-Wilczek estimates. In addition, in the spectral model we evaluate the distribution amplitudes and light-cone wave functions of the $\rho$-meson.

Recently a new method for determining the neutrino mass hierarchy by comparing the effective values of the atmospheric $\Delta m^2$ measured in the electron neutrino disappearance channel, $\Delta m^2(\mathrm{ee})$, with the one measured in the muon neutrino disappearance channel, $\Delta m^2(\mu \mu )$, was proposed. If $\Delta m^2(\mathrm{ee})$ is larger (smaller) than $\Delta m^2(\mu \mu )$ the hierarchy is of the normal (inverted) type. We reexamine this proposition in the light of two very high precision measurements: $\Delta m^2(\mu \mu )$ that may be accomplished by the phase II of the Tokai-to-Kamioka (T2K) experiment, for example, and $\Delta m^2(\mathrm{ee})$ that can be envisaged using the novel Mössbauer enhanced resonant ${\overline{\nu }}_e$ absorption technique. Under optimistic assumptions for the systematic uncertainties of both measurements, we estimate the parameter region of (${\theta }_{13}$, $\delta$) in which the mass hierarchy can be determined. If ${\theta }_{13}$ is relatively large, ${sin}^{2}2{\theta }_{13}\gtrsim 0.05$, and both of $\Delta m^2(\mathrm{ee})$ and $\Delta m^2(\mu \mu )$ can be measured with the precision of $\sim 0.5\%$ it is possible to determine the neutrino mass hierarchy at $>95\%$ CL for $0.3\pi \lesssim \delta \lesssim 1.7\pi$ for the current best fit values of all the other oscillation parameters.

We search for $B^0$ meson decays into two-body combinations of $K^0$, $\eta$, ${\eta }^{\prime }$, and $\varphi$ mesons in $324\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider at SLAC. We measure the following branching fractions (upper limits at 90% confidence level) in units of ${10}^{-6}$: $\mathcal{B}(B^0\to \eta K^0)={1.8}_{-0.6}^{+0.7}\pm 0.1(<2.9)$, $\mathcal{B}(B^0\to \eta \eta )={1.1}_{-0.4}^{+0.5}\pm 0.1(<1.8)$, $\mathcal{B}(B^0\to \eta \varphi )=0.1\pm 0.2\pm 0.1(<0.6)$, $\mathcal{B}(B^0\to {\eta }^{\prime }\varphi )={0.2}_{-0.3}^{+0.4}\pm 0.1(<1.0)$, and $\mathcal{B}(B^0\to {\eta }^{\prime }{\eta }^{\prime })={1.0}_{-0.6}^{+0.8}\pm 0.1(<2.4)$, where the first error is statistical and the second systematic.

We study first the Hamiltonian operator H corresponding to the Fock-Weyl extension of the Dirac equation to gravitation. When searching for stationary solutions to this equation, in a static metric, we show that just one invariant Hermitian product appears natural. In the case of a space-isotropic metric, H is Hermitian for that product. Then we investigate the asymptotic post-Newtonian approximation of the stationary Schrödinger equation associated with H, for a slow particle in a weak-field static metric. We rewrite the expanded equations as one equation for a two-component spinor field. This equation contains just the nonrelativistic Schrödinger equation in the gravity potential, plus correction terms. Those “correction” terms are of the same order in the small parameter as the main terms, but are numerically negligible in the case of ultracold neutrons in the Earth’s gravity.

We study the cosmological evolution on a brane with induced gravity within a bulk with arbitrary matter content. We consider a Friedmann-Robertson-Walker brane, invariantly characterized by a six-dimensional group of isometries. We derive the effective Friedmann and Raychaudhuri equations. We show that the Hubble expansion rate on the brane depends on the covariantly defined integrated mass in the bulk, which determines the energy density of the generalized dark radiation. The Friedmann equation has two branches, distinguished by the two possible values of the parameter $ϵ=\pm 1$. The branch with $ϵ=1$ is characterized by an effective cosmological constant and accelerated expansion for low energy densities. Another remarkable feature is that the contribution from the generalized dark radiation appears with a negative sign. As a result, the presence of the bulk corresponds to an effective negative energy density on the brane, without violation of the weak energy condition. The transition from a period of domination of the matter energy density by nonrelativistic brane matter to domination by the generalized dark radiation corresponds to a crossing of the phantom divide $w=-1$.

The annihilation of light dark matter was recently advocated as a possible explanation of the large positron injection rate at the Galactic center deduced from observations by the SPI spectrometer aboard INTEGRAL. The modelling of internal Bremsstrahlung and in-flight annihilation radiations associated to this process drastically reduced the mass range of this light dark matter particle. We estimate critically the various energy losses and radiations involved in the propagation of the positron before its annihilation—in-flight or at rest. Using a simple model with monoenergetic positrons injected and confined to the Galactic bulge, we compute energy losses and gamma-ray radiations caused by ionization, Bremsstrahlung interactions as well as in-flight and at rest annihilation and compare these predictions to the available observations, for various injection energies. Confronting the predictions with observations by the CGRO/EGRET, CGRO/COMPTEL, INTEGRAL/SPI, and INTEGRAL/IBIS/ISGRI instruments, we deduce a mass upper bound of 3 to $7.5\mathrm{MeV}/c^2$ for the hypothetical light dark matter particle. The most restrictive limit is in agreement with the value previously found by Beacom and Yüksel and was obtained under similar assumptions, while the $7.5\mathrm{MeV}/c^2$ value corresponds to more conservative choices and to a partially ionized propagation medium. We stress how the limit depends on the degree of ionization of the propagation medium and how its precision could be improved by a better appraisal of data uncertainties.

We discuss the relevance, for the search of gravitational-wave bursts, of upper limits on the total mass loss of the Galaxy which come from various astronomical observations. For submillisecond bursts we obtain limits on the event rate, as a function of the GW amplitude, which are stronger than the corresponding upper limits set by LIGO in the S2 run. Detection of a burst rate saturating these limits, with the sensitivities of present and near-future runs, would imply that, with some improvement on the accuracy of astronomical observations of the Galaxy, as foreseen with the GAIA mission, it might be possible to detect gravitational waves indirectly from their effect on galactic dynamics.

We present a novel method based on wavelet packet transformation for detection of gravitational wave (gw) bursts embedded in additive Gaussian noise. The method exploits a wavelet packet decomposition of observed data and performs detection of bursts at multiple time-frequency resolutions by the extreme value statistics. We discuss the performances of detection algorithms (efficiency and robustness) in the general framework of hypothesis testing. In particular, we compare the performances of wavelet packet (WP), matched filter (MF), and power filter (PF) algorithms by means of a complete Monte Carlo simulation of the output of a gw detector, with the detection efficiencies of MF and PF playing the role of upper and lower bounds, respectively. Moreover, the performances of impulsive filter (IF) algorithm, widely used in the data analysis of resonant gw detectors, have been investigated. Results we get by injecting chirplet signals confirm the expected performances in terms of efficiency and robustness. To illustrate the application of the new method to real data, we analyzed a few data sets of the resonant gw detector AURIGA.

We propose a scenario of gravity mediated supersymmetry breaking (gravity mediation) in a supersymmetric Randall-Sundrum model. In our setup, both the visible sector and the hidden sector coexist on the infrared (IR) brane. We introduce the Polonyi model as a simple hidden sector. Because of the warped metric, the effective cutoff scale on the IR brane is “warped down,” so that the gravity mediation occurs at a low scale. As a result, the gravitino is naturally the lightest superpartner (LSP) and contact interactions between the hidden and the visible sector fields become stronger. We address phenomenologies for various IR cutoff scales. In particular, we investigate collider phenomenology involving a scalar field (Polonyi field) in the hidden sector for the case with the IR cutoff around 10 TeV. We find a possibility that the hidden sector scalar can be produced at the LHC and the international linear collider (ILC). Interestingly, the scalar behaves like the Higgs boson of the standard model in the production process, while its decay process is quite different and, once produced, it will provide us with a very clean signature. The hidden sector may be no longer hidden.

We construct a new off-shell $N=4$, $d=3$ nonlinear vector supermultiplet. The irreducibility constraints for the superfields leave in this supermultiplet the same component content as in the ordinary linear vector supermultiplet. We present the most general sigma-model type action for the $N=4$, $d=3$ electrodynamics with the nonlinear vector supermultiplet, which despite the nonlinearity of the supermultiplet may be written as an integral over a chiral superspace. This action shares the most important properties with its linear counterpart. We also perform the dualization of the vector component into a scalar one and find the corresponding $N=4$, $d=3$ supersymmetric action which describes new hyper-Kähler sigma-model in the bosonic sector.

We extend the worldline instanton technique to compute the vacuum pair production rate for spatially inhomogeneous electric background fields, with the spatial inhomogeneity being genuinely two or three dimensional, both for the magnitude and direction of the electric field. Other techniques, such as WKB, have not been applied to such higher dimensional problems. Our method exploits the instanton dominance of the worldline path integral expression for the effective action.

A classical field theory is proposed for the electric current and the electromagnetic field interpolating between microscopic and macroscopic domains. It represents a generalization of the density functional for the dynamics of the current and the electromagnetic field in the quantum side of the crossover and reproduces standard classical electrodynamics on the other side. The effective action derived in the closed time path formalism and the equations of motion follow from the variational principle. The polarization of the Dirac-sea can be taken into account in the quadratic approximation of the action by the introduction of the deplacement field strengths as in conventional classical electrodynamics. Decoherence appears naturally as a simple one-loop effect in this formalism. It is argued that the radiation time arrow is generated from the quantum boundary conditions in time by decoherence at the quantum-classical crossover and the Abraham-Lorentz force arises from the accelerating charge or from other charges in the macroscopic or the microscopic side, respectively. The functional form of the quantum renormalization group, the generalization of the renormalization group method for the density matrix, is proposed to follow the scale dependence through the quantum-classical crossover in a systematical manner.

Higher-dimensional models of neutrino physics with one or more right-handed neutrinos in the bulk have attracted considerable attention in recent years. However, a critical issue for such models is to find a way of introducing the required flavor dependence needed for generating neutrino oscillations. In this paper, we point out that a natural minimal framework that accomplishes this can be constructed by combining the bulk-neutrino hypothesis for right-handed neutrinos with the split-fermion scenario for left-handed neutrinos. This combination leads to a unique flavor signature for neutrino phenomenology which easily incorporates large flavor mixing angles. This hybrid scenario also has a number of additional important features. For example, one previous difficulty of the split-fermion scenario applied to neutrinos has been that the mass matrix is exponentially sensitive to neutrino displacements within the brane. However, in our hybrid scenario, the interactions between the brane and bulk naturally convert this dependence from exponential to linear. Another important feature is that our hybrid scenario provides its own natural regulator for Kaluza-Klein sums. Thus, in our scenario, all Kaluza-Klein summations are manifestly finite, even in cases with multiple extra dimensions. But most importantly, our mechanism completely decouples the effective neutrino flavor mixing angles from the sizes of the overlaps between the neutrino wave functions within the brane. Thus, we are able to obtain large neutrino mixing angles even when these neutrinos have significant spatial separations and their overlaps vanish.

We consider the leading one-chain term in a skeleton expansion for QCD observables and show that for energies $Q^2>{\Lambda }^2$, where $Q^2={\Lambda }^2$ is the Landau pole of the coupling, the skeleton expansion result is equivalent to the standard Borel integral representation, with ambiguities related to infrared (IR) renormalons. For $Q^2<{\Lambda }^2$ the skeleton expansion result is equivalent to a previously proposed modified Borel representation where the ambiguities are connected with ultraviolet (UV) renormalons. We investigate the $Q^2$-dependence of the perturbative corrections to the Adler-$D$ function, the GLS sum rule and the polarized and unpolarized Bjorken sum rules. In all these cases the one-chain result changes sign in the vicinity of $Q^2={\Lambda }^2$, and then exhibits freezing behavior, vanishing at $Q^2=0$. Finiteness at $Q^2={\Lambda }^2$ implies specific relations between the residues of IR and UV renormalon singularities in the Borel plane. These relations, only one of which has previously been noted (though it remained unexplained), are shown to follow from the continuity of the characteristic function in the skeleton expansion. By considering the compensation of nonperturbative and perturbative ambiguities we are led to a result for the $Q^2$-dependence of these observables at all $Q^2$, in which there is a single undetermined nonperturbative parameter, and which involves the skeleton expansion characteristic function. The observables freeze to zero in the infrared. We briefly consider the freezing behavior of the Minkowskian $R_{e^{+}{e}^{-}}$ ratio.

A first step in the analysis of the renormalizability of gravity at large $\mathbf{N}$ is carried out. Suitable resummations of planar diagrams give rise to a theory in which there is only a finite number of primitive, superficially divergent, Feynman diagrams. The mechanism is similar to the one which makes the 3D Gross-Neveu model renormalizable at large $\mathbf{N}$. The connections with gravitational confinement and Kawai-Lewellen-Tye relations are briefly analyzed. Some potential problems in fulfilling the Zinn-Justin equations are pointed out.

Fermi coordinates are directly constructed in de Sitter and Gödel spacetimes and the corresponding exact coordinate transformations are given explicitly. The quasi-inertial Fermi coordinates are then employed to discuss the dynamics of a free test particle in these spacetimes and the results are compared to the corresponding generalized Jacobi equations that contain only the lowest-order tidal terms. The domain of validity of the generalized Jacobi equation is thus examined in these cases. Furthermore, the difficulty of constructing explicit Fermi coordinates in black hole spacetimes is demonstrated.