We have surveyed leptonic and grand unified models of neutrino masses and mixings in the literature which are still viable and give numerical predictions for the reactor angle, ${\theta }_{13}$. The results are of considerable interest in anticipation of the next generation reactor experiments and the possible future need for neutrino factories. Of the 63 models considered which were published or posted on the Archive before June 2006, half predict values of ${sin}^{2}2{\theta }_{13}\gtrsim 0.015$, which should yield positive signals for ${\overline{\nu }}_e$ disappearance in the reactor experiments planned for the near future. Depending upon the outcome of those experiments, half of the models can be eliminated on the basis of the presence or absence of such an observed ${\overline{\nu }}_e$ disappearance signal.

It is shown that nuggets of strange quark matter may be extracted from the surface of pulsars and accelerated by strong electric fields to high energies if pulsars are strange stars with the crusts, comprised of nuggets embedded in a uniform electron background. Such high energy nuggets called usually strangelets give an observable contribution into galactic cosmic rays and may be detected by the upcoming cosmic ray experiment Alpha Magnetic Spectrometer AMS-02 on the International Space Station.

We discuss the amplitudes describing $N$-gluon scattering in type I superstring theory, on a disk world sheet. After reviewing the general structure of amplitudes and the complications created by the presence of a large number of vertices at the boundary, we focus on the most promising case of maximally helicity violating (MHV) configurations because in this case, the zero Regge slope limit (${\alpha }^{\prime }\to 0$) is particularly simple. We obtain the full-fledged MHV disk amplitudes for $N=4$, 5, and $N=6$ gluons, expressed in terms of one, two and six functions of kinematic invariants, respectively. These functions represent certain boundary integrals—generalized Euler integrals—which for $N\ge 6$ correspond to multiple hypergeometric series (generalized Kampé de Fériet functions). Their ${\alpha }^{\prime }$ expansions lead to Euler-Zagier sums. For arbitrary $N$, we show that the leading string corrections to the Yang-Mills amplitude, of order $\mathcal{O}({\alpha }^{\prime 2})$, originate from the well-known ${\alpha }^{\prime 2}\mathrm{Tr}{F}^4$ effective interactions of four gauge field strength tensors. By using iteration based on the soft gluon limit, we derive a simple formula valid to that order for arbitrary $N$. We argue that such a procedure can be extended to all orders in ${\alpha }^{\prime }$. If nature gracefully picked a sufficiently low string mass scale, our results would be important for studying string effects in multijet production at the Large Hadron Collider (LHC).

We consider noncanonical embeddings of the MSSM in high-dimensional orbifold grand unified theories (GUTs) based on the gauge symmetry $SU(N)$, $N=5$, 6, 7, 8. The hypercharge normalization factor $k_Y$ can either have unique noncanonical values, such as $23/21$ in a six-dimensional $SU(7)$ model, or may lie in a (continuous) interval. Gauge coupling unification and gauge-Yukawa unification can be realized in these models by introducing new particles with masses in the TeV range which may be found at the LHC. In one such example there exist color singlet fractionally charged states.

We find a strong-to-weak coupling crossover in $D=2+1$ $SU(N)$ lattice gauge theories that appears to become a third-order phase transition at $N=\infty$, in a similar way to the Gross-Witten transition in the $D=1+1$ $SU(N\to \infty )$ lattice gauge theory. There is, in addition, a peak in the specific heat at approximately the same coupling that increases with $N$, which is connected to $Z_N$ monopoles (instantons), reminiscent of the first-order bulk transition that occurs in $D=3+1$ lattice gauge theories for $N\ge 5$. Our calculations are not precise enough to determine whether this peak is due to a second-order phase transition at $N=\infty$ or to the third-order phase transition having a critical behavior different to that of the Gross-Witten transition. We show that as the lattice spacing is reduced, the $N=\infty$ gauge theory on a finite 3-torus appears to undergo a sequence of first-order $Z_N$ symmetry breaking transitions associated with each of the tori (ordered by size). We discuss how these transitions can be understood in terms of a sequence of deconfining transitions on ever-more dimensionally reduced gauge theories. We investigate whether the trace of the Wilson loop has a nonanalyticity in the coupling at some critical area, but find no evidence for this. However we do find that, just as one can prove occurs in $D=1+1$, the eigenvalue density of a Wilson loop forms a gap at $N=\infty$ at a critical value of its trace. We show that this gap formation is in fact a corollary of a remarkable similarity between the eigenvalue spectra of Wilson loops in $D=1+1$ and $D=2+1$ (and indeed $D=3+1$): for the same value of the trace, the eigenvalue spectra are nearly identical. This holds for finite as well as infinite $N$; irrespective of the Wilson loop size in lattice units; and for Polyakov as well as Wilson loops.

We analyze the motion of massless and massive particles around black holes immersed in an asymptotically uniform magnetic field and surrounded by some mechanical structure, which provides the magnetic field. The space-time is described by the Preston-Poisson metric, which is the generalization of the well-known Ernst metric with a new parameter, tidal force, characterizing the surrounding structure. The Hamilton-Jacobi equations allow the separation of variables in the equatorial plane. The presence of a tidal force from the surroundings considerably changes the parameters of the test particle motion: it increases the radius of circular orbits of particles and increases the binding energy of massive particles going from a given circular orbit to the innermost stable orbit near the black hole. In addition, it increases the distance of the minimal approach, time delay, and bending angle for a ray of light propagating near the black hole.

The covariant gauge-invariant perturbation theory of scalar cosmological perturbations is developed for a general scalar-tensor Friedmann-Lemaitre-Robertson-Walker cosmology in a vacuum. The perturbation equations are then solved exactly in the long wavelength limit for a specific coupling, potential, and background. Differences with the minimally coupled case are briefly discussed.

Cosmological perturbation equations are derived systematically in a canonical scheme based on Ashtekar variables. A comparison with the covariant derivation and various subtleties in the calculation and choice of gauges are pointed out. Nevertheless, the treatment is more systematic when correction terms of canonical quantum gravity are to be included. This is done throughout the paper for one example of characteristic modifications expected from loop quantum gravity.

Shortly after the addition of a $1/R$ term to the Einstein-Hilbert action was proposed as a solution to the cosmic-acceleration puzzle, Chiba showed that such a theory violates Solar System tests of gravity. A flurry of recent papers have called Chiba’s result into question. They argue that the spherically-symmetric vacuum spacetime in this theory is the Schwarzschild-de Sitter solution, making this theory consistent with Solar System tests. We point out that although the Schwarzschild-de Sitter solution exists in this theory, it is not the unique spherically-symmetric vacuum solution, and it is not the solution that describes the spacetime in the Solar System. The solution that correctly matches onto the stellar-interior solution differs from Schwarzschild-de Sitter in a way consistent with Chiba’s claims. Thus, $1/R$ gravity is ruled out by Solar System tests.

We study radiative neutralino production $e^{+}{e}^{-}\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0\gamma$ at the linear collider with longitudinally polarized beams. We consider the standard model background from radiative neutrino production $e^{+}{e}^{-}\to \nu \overline{\nu }\gamma$, and the supersymmetric radiative production of sneutrinos $e^{+}{e}^{-}\to \tilde{\nu }{\tilde{\nu }}^{*}\gamma$, which can be a background for invisible sneutrino decays. We give the complete tree-level formulas for the amplitudes and matrix elements squared. In the minimal supersymmetric standard model, we study the dependence of the cross sections on the beam polarizations, on the parameters of the neutralino sector, and on the selectron masses. We show that for $b$-inolike neutralinos longitudinal polarized beams enhance the signal and simultaneously reduce the background, such that statistics is significantly enhanced. We point out that there are parameter regions where radiative neutralino production is the only channel to study SUSY particles, since heavier neutralinos, charginos and sleptons are too heavy to be pair-produced in the first stage of the linear collider with $\sqrt{s}=500\mathrm{GeV}$.

Neutrino telescopes may have the potential to detect the quasistable staus predicted by some supersymmetric models. Detection depends on stau electromagnetic energy loss and weak interactions. We present results for the weak interactions contribution to the energy loss of high energy staus as they pass through rock. We show that the neutral-current weak interaction contribution is much smaller than photonuclear energy loss, however, the charged-current contribution may become dominant process above an energy of $\sim {10}^9\mathrm{GeV}$. As a consequence, the stau range may be reduced above $\sim {10}^9\mathrm{GeV}$ as compared to the range neglecting weak interactions. We contrast this with the case of tau range, which is barely changed with the inclusion of charged-current interactions.

The role of the strange quark mass for the phase structure of QCD at nonvanishing densities is studied by employing a recently developed self-consistent truncation scheme for the Dyson-Schwinger equations of the quark propagators in Landau gauge. Hereby the medium modification of the effective quark interaction by the polarization of gluons is implemented. Taking into account this effect results in significantly smaller dynamical quark masses at the Fermi surface. Because of this reduction the color-flavor locked phase is always the preferred color-superconducting phase at zero temperature and for a realistic strange quark mass.

We analyze the consequences of the inclusion of the gluonic Polyakov loop in chiral quark models at low temperature in the light of chiral perturbation theory. Specifically, the low-energy effective chiral Lagrangian from two such quark models is computed. The tree level vacuum energy density, quark condensate, pion decay constant, and Gasser-Leutwyler coefficients are found to acquire a temperature dependence. This dependence is, however, exponentially small for temperatures below the mass gap in the full unquenched calculation. The introduction of the Polyakov loop and its quantum fluctuations is essential to achieve this result and also the correct large $N_c$ counting for the thermal corrections. We find that new coefficients are introduced at $\mathcal{O}(p^4)$ to account for the Lorentz breaking at finite temperature. As a byproduct, we obtain the effective Lagrangian which describes the coupling of the Polyakov loop to the Goldstone bosons.

We study the single-spin (left-right) asymmetry in single-inclusive pion production in hadronic scattering. This asymmetry is power-suppressed in the transverse momentum of the produced pion and can be analyzed in terms of twist-three parton correlation functions in the proton. We present new calculations of the corresponding partonic hard-scattering functions that include the so-called “nonderivative” contributions not previously considered in the literature. We find a remarkably simple structure of the results. We also present a brief phenomenological study of the spin asymmetry, taking into account data from fixed-target scattering and also the latest information available from Relativistic Heavy Ion Collider (RHIC). We make additional predictions that may be tested experimentally at RHIC.

We report on a measurement of the $B_d^0$ mixing frequency and the calibration of an opposite-side flavor tagger in the D0 experiment. Various properties associated with the $b$ quark on the opposite side of the reconstructed $B$ meson are combined using a likelihood-ratio method into a single variable with enhanced tagging power. Its performance is tested with data, using a large sample of reconstructed semileptonic $B\to \mu D^{0}X$ and $B\to \mu D^{*}X$ decays, corresponding to an integrated luminosity of approximately $1{\mathrm{fb}}^{-1}$. The events are divided into groups depending on the value of the combined tagging variable, and an independent analysis is performed in each group. Combining the results of these analyses, the overall effective tagging power is found to be $\epsilon {\mathcal{D}}^2=(2.48\pm {0.21}_{-0.06}^{+0.08})\%$. The measured $B_d^0$ mixing frequency $\Delta m_d=0.506\pm 0.020(\mathrm{stat})\pm 0.016(\mathrm{syst}){\mathrm{ps}}^{-1}$ is in good agreement with the world average value.

Conformally invariant wave equations in de Sitter space, for scalar and vector fields, are introduced in the present paper. Solutions of their wave equations and the related two-point functions, in the ambient space notation, have been calculated. The Hilbert space structure and the field operator, in terms of coordinate independent de Sitter plane waves, have been defined. The construction of the paper is based on the analyticity in the complexified pseudo-Riemannian manifold, presented first by Bros et al. Minkowskian limits of these functions are analyzed. The relation between the ambient space notation and the intrinsic coordinates is then studied in the final stage.

Considering that the momentum squared in the extra dimensions is the physically relevant quantity for the generation of the Kaluza-Klein mass states, we have reanalyzed mathematically the procedure for five dimensional scalar fields within the Arkhani-Ahmed, Dimopoulos and Dvali scenario. We find new sets of physically allowed boundary conditions. Beside the usual results, they lead to new towers with non regular mass spacing, to lonely mass states and to tachyons.

Recent direct searches for new massive particles place constraints on the free parameters of the littlest Higgs model. Depending on the choice of model free parameters, the direct-search limit on the global symmetry-breaking scale $f$ can range from as low as a few hundred GeV to in excess of 4.5 TeV. The most stringent constraints are from exclusion of the $A_H$ using high-mass dilepton resonance searches. The $Z_H$ provides the best constraint in parameter regions where the $A_H$ decouples from leptons. Current top pair resonance data approach but do not yet reach a useful limit in the anomaly-cancelling case, but do provide a constraint for a limited range of parameters in other cases. A neutral gauge boson is shown to be undetectable in dilepton resonances for a significant range of parameter space due to decoupling from standard model leptons, providing a counterexample to broad claims that a new neutral gauge boson (sometimes generically referred to as a $Z^{\prime }$) is ruled out to a high-mass scale.

We determine the weak interaction corrections of order ${\alpha }_s^2\alpha$ to hadronic top-quark pair production. First we compute the one-loop weak corrections to $t\overline{t}$ production due to gluon fusion and the order ${\alpha }_s^2\alpha$ corrections to $t\overline{t}$ production due to (anti)quark-gluon scattering in the standard model. With our previous result [W. Bernreuther, M. Fücker, and Z. G. Si, Phys. Lett. B 633, 54 (2006).] this yields the complete corrections of order ${\alpha }_s^2\alpha$ to $gg$, $q\overline{q}$, $qg$, and $\overline{q}g$ induced hadronic $t\overline{t}$ production with $t$ and $\overline{t}$ polarizations and spin correlations fully taken into account. For the Tevatron and the LHC we determine the weak contributions to the transverse top momentum and to the $t\overline{t}$ invariant-mass distributions. At the LHC these corrections can be of the order of 10% compared with the leading-order results, for large $p_T$ and $M_{t\overline{t}}$, respectively. Apart from parity-even $t\overline{t}$ spin correlations we analyze also parity-violating double- and single-spin asymmetries and show how they are related if $CP$ invariance holds. For $t$ (and $\overline{t}$) quarks which decay semileptonically, we compute a resulting charged-lepton forward-backward asymmetry $A_{PV}$ with respect to the $t$ ($\overline{t}$) direction, which is of the order of 1% at the LHC for suitable invariant-mass cuts.

We present the results of the first exposure of a Liquid Argon TPC to a multi-GeV neutrino beam. The data have been collected with a 50 liters ICARUS-like chamber located between the CHORUS and NOMAD experiments at the CERN West Area Neutrino Facility (WANF). We discuss both the instrumental performance of the detector and its capability to identify and reconstruct low-multiplicity neutrino interactions.