This paper complements the study of single top-quark production at the CERN LHC aiming to estimate the sensitivity of different observables to the magnitude of the effective couplings. In a previous paper the dominant W-gluon fusion mechanism was considered, while here we extend the analysis to the subdominant (10% with our set of experimental cuts) s-channel process. In order to distinguish left from right effective couplings it is required to consider polarized cross sections and/or include $m_b$ effects. The spin of the top quark is accessible only indirectly by measuring the angular distribution of its decay products. We show that the presence of effective right-handed couplings implies necessarily that the top quark is not in a pure spin state. We discuss to what extent quantum interference terms can be neglected in the measurement and therefore simply multiply production and decay probabilities classically. The coarsening involved in the measurement process makes this possible. We determine for each process the optimal spin basis where theoretical errors are minimized and, finally, discuss the sensitivity in the s channel to the effective right-handed coupling. The results presented here are all analytical and include $m_b$ corrections. They are derived within the narrow width approximation for the top quark.

Magnetic moments of octet and ${\Omega }^{-}$ baryons have been calculated employing the concepts of effective mass and screened charge. The magnetic moments obtained compare well with their experimental counterparts.

Developments in deeply virtual Compton scattering allow the direct measurements of scattering amplitudes for exchange of a highly virtual photon with fine spatial resolution. Real-space images of the target can be obtained from this information. Spatial resolution is determined by the momentum transfer rather than the wavelength of the detected photon. Quantum photographs of the proton, nuclei, and other elementary particles with resolution on the scale of a fraction of a femtometer are feasible with existing experimental technology.

The NuTeV Collaboration reported an anomalously large weak mixing angle ${\sin }^2{\theta }_W$ in comparison with the standard model prediction. Neutrino and antineutrino charged- and neutral-current events are analyzed for extracting ${\sin }^2{\theta }_W.$ Although the Paschos-Wolfenstein relation is not directly used in the analysis, it plays an important role in the determination. Noting that the target nucleus, iron, is not an isoscalar nucleus, we derive a leading-order expression for a modified Paschos-Wolfenstein relation for nuclei, which may have neutron excess. Then, using charge and baryon-number conservations for nuclei, we discuss a nuclear correction in the ${\sin }^2{\theta }_W$ determination. It is noteworthy that nuclear modifications are different between valence up- and down-quark distributions. We show this difference effect on the NuTeV ${\sin }^2{\theta }_W$ deviation.

We found a gravity solution of a $p+1\mathrm{}$ dimensional extended object with $\mathrm{SO}\left(p\right)\mathrm{}\times SO\left(9\mathrm{}-p\right)$ symmetry which has zero pressure and zero dilaton charge. We expect that this object is a residual tachyon dust after tachyon condensation of the brane and antibrane system recently discussed by Sen. We also discuss the Hawking temperature and some properties of this object.

We propose a spin foam model for pure gauge fields coupled to Riemannian quantum gravity in four dimensions. The model is formulated for the triangulation of a four-manifold which is given merely combinatorially. The Riemannian Barrett-Crane model provides the gravity sector of our model and dynamically assigns geometric data to the given combinatorial triangulation. The gauge theory sector is a lattice gauge theory living on the same triangulation and obtains from the gravity sector the geometric information which is required to calculate the Yang-Mills action. The model is designed so that one obtains a continuum approximation of the gauge theory sector at an effective level, similarly to the continuum limit of lattice gauge theory, when the typical length scale of gravity is much smaller than the Yang-Mills scale.

Hawking radiation can usefully be viewed as a semiclassical tunneling process that originates at the black hole horizon. The same basic premise should apply to de Sitter background radiation, with the cosmological horizon of de Sitter space now playing the featured role. In fact, a recent work (M. K. Parikh, hep-th/0204107) has gone a long way to verifying the validity of this de Sitter–tunneling picture. In the current paper, we extend these prior considerations to arbitrary-dimensional de Sitter space, as well as Schwarzschild–de Sitter spacetimes. It is shown that the tunneling formalism naturally censors against any black hole with a mass in excess of the Nariai value, thus enforcing a “third law” of Schwarzschild–de Sitter thermodynamics. We also provide commentary on the dS/conformal field theory correspondence in the context of this tunneling framework.

We show why the universe started in an unstable de Sitter state. The quantum origin of our universe implies one must take a “top down” approach to the problem of initial conditions in cosmology, in which the histories that contribute to the path integral depend on the observable being measured. Using the no boundary proposal to specify the class of histories, we study the quantum cosmological origin of an inflationary universe in theories such as trace anomaly driven inflation in which the effective potential has a local maximum. We find that an expanding universe is most likely to emerge in an unstable de Sitter state, by semiclassical tunneling via a Hawking-Moss instanton. Since the top down view is forced upon us by the quantum nature of the universe, we argue that the approach developed here should still apply when the framework of quantum cosmology will be based on M theory.

The Cryogenic Dark Matter Search (CDMS) employs low-temperature Ge and Si detectors to search for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei while discriminating against interactions of background particles. For recoil energies above 10 keV, events due to background photons are rejected with $>99.9\%$ efficiency, and surface events are rejected with $>95\%$ efficiency. The estimate of the background due to neutrons is based primarily on the observation of multiple-scatter events that should all be neutrons. Data selection is determined primarily by examining calibration data and vetoed events. Resulting efficiencies should be accurate to $\sim 10\%.$ Results of CDMS data from 1998 and 1999 with a relaxed fiducial-volume cut (resulting in 15.8 kg days exposure on Ge) are consistent with an earlier analysis with a more restrictive fiducial-volume cut. Twenty-three WIMP candidate events are observed, but these events are consistent with a background from neutrons in all ways tested. Resulting limits on the spin-independent WIMP-nucleon elastic-scattering cross section exclude unexplored parameter space for WIMPs with masses between $10–70\mathrm{GeV}{/c}^2.$ These limits border, but do not exclude, parameter space allowed by supersymmetry models and accelerator constraints. Results are compatible with some regions reported as allowed at $3\sigma$ by the annual-modulation measurement of the DAMA Collaboration. However, under the assumptions of standard WIMP interactions and a standard halo, the results are incompatible with the DAMA most likely value at $>99.9\%$ confidence level (C.L.), and are incompatible with the model-independent annual-modulation signal of DAMA at $99.99\%$ C.L. in the asymptotic limit.

We obtain differential cross sections for the reaction $e^{-}+\overrightarrow{p}\Lambda +{\nu }_e,$ for several incident electron energies near threshold. We are motivated to examine this reaction because it has been proposed as a possible experiment at the Thomas Jefferson National Accelerator Facility to measure the electron neutrino mass. We choose electron energies of 194.25 MeV, 195 MeV, 200 MeV, and 205 MeV so that trends in the cross section may be examined. This calculation is phenomenologically based and makes use of $\mathrm{SU}\left(3\right)\mathrm{}$ relations, and the form factors so obtained accurately describe $\Lambda$ beta decay and so should be correct in this region. We obtain contributions of the individual form factors to the differential cross section and show that the axial vector current form factor increasingly dominates as the electron energy nears threshold. Finally we discuss how the behavior of the cross section in the near threshold region affects its use as a tool to study the electron neutrino mass as has recently been proposed.

We investigate supersymmetric ${\mathrm{SU}\left(4\right)\mathrm{}}_c\times {\mathrm{SU}\left(4\right)\mathrm{}}_{L+R}$ theory in five dimensions whose compactification on an $S^{\mathrm{}\left(1\right)\mathrm{}}{/Z}_2$ orbifold yields $N=1\mathrm{}$ supersymmetric ${\mathrm{SU}\left(4\right)\mathrm{}}_c\times {\mathrm{SU}\left(2\right)\mathrm{}}_L\times {\mathrm{SU}\left(2\right)\mathrm{}}_R$ supplemented by a $Ũ\mathrm{}\left(1\right)\mathrm{}$ gauge symmetry. We discuss how the $\mu$ problem is resolved, a realistic Yukawa sector achieved, and a stable proton realized. Neutrino masses and oscillations are also briefly discussed.

We study grand unified theories (GUT) based on an $\mathrm{SU}\left(5\right)\mathrm{}\times \mathrm{SU}\left(5\right)\mathrm{}$ gauge group in which the GUT scale, $M_{\mathrm{GUT}},$ is the vacuum expectation value of an exact or approximate modulus, and in which fast proton decay is avoided through a combination of a large triplet mass and small triplet couplings. These features are achieved by discrete symmetries. In many of our models, $M_{\mathrm{GUT}}$ is generated naturally by the balance of higher dimension terms that lift the GUT modulus potential, and soft supersymmetry breaking masses. The theories often lead to interesting patterns of quark and lepton masses. We also discuss some distinctions between grand unified theories and string unification.

In this paper we examine the production channels for the scalar or pseudoscalar Higgs boson plus two jets at the CERN Large Hadron Collider. We identify possible signals for distinguishing between a scalar and a pseudoscalar Higgs boson.

The $\left[\mathrm{U}\mathrm{}\right(1)\mathrm{}{]}^{N-1}$ dual Ginzburg-Landau (DGL) theory as a low-energy effective theory of Abelian-projected $\mathrm{SU}\mathrm{}\left(N\right)\mathrm{}$ gauge theory is formulated in a Weyl symmetric way. The string tensions of the flux-tube solutions of the DGL theory associated with color-electric charges in various representations of $\mathrm{SU}\mathrm{}\left(N\right)\mathrm{}$ are calculated analytically at the border between type I and type II of the dual superconducting vacuum (Bogomol’nyi limit). The resulting string tensions satisfy the flux counting rule, which reflects the non-Abelian nature of gauge theory.

In the democratic universal seesaw model, the mass matrices are given by $f_L{m}_L{F}_R+F_L{m}_R{f}_R+F_L{M}_F{F}_R$ $(f:$ quarks and leptons; F: hypothetical heavy fermions), $m_L$ and $m_R$ are universal for up and down fermions, and $M_F$ has the structure $\left(1{+b}_{f}X\right){(b}_f$ is a flavor-dependent parameter, and X is a democratic matrix). The model can successfully explain the quark masses and Cabibbo-Kobayashi-Maskawa mixing parameters in terms of the charged lepton masses by adjusting only one parameter $b_f.$ However, so far, the model has not been able to give the observed bimaximal mixing for the neutrino sector. In the present paper, we consider that $M_F$ in the quark sectors are still “fully” democratic, while $M_F$ in the lepton sectors are partially democratic. Then the revised model can reasonably give a nearly bimaximal mixing without spoiling the previous success in the quark sectors.

We describe a search for evidence of minimal supergravity (MSUGRA) in $92.7{\mathrm{pb}}^{-1}$ of data collected with the DØ detector at the Fermilab Tevatron $p\overline{p}$ collider at $\sqrt{s}=1.8\mathrm{}\mathrm{TeV}.$ Events with a single electron, four or more jets, and large missing transverse energy were used in this search. The major backgrounds are from $W+\mathrm{jets},$ misidentified multijet, $t\overline{t},$ and $\mathrm{WW}$ production. We observe no excess above the expected number of background events in our data. A new limit in terms of MSUGRA model parameters is obtained.

We present several supergravity solutions corresponding to both $\mathrm{D}p$ and $\mathrm{D}p-\mathrm{D}{p}^{\prime }$ systems, in Neveu-Schwarz–Neveu-Schwarz and Ramond-Ramond $\mathrm{pp}$-wave background originating from ${\mathrm{AdS}}_3\times {\mathrm{S}}^3\times {\mathrm{R}}^4.$ The $\mathrm{D}p$-brane solutions, $p=1,\dots ,5\mathrm{}$ are fully localized, whereas $\mathrm{D}p-\mathrm{D}{p}^{\prime }$ solutions are localized along common transverse directions. We also discuss the supersymmetry properties of these solutions and the worldsheet construction for the $p-p^{\prime }$ system.

We study the question of generalizing light-front field theories to finite temperature. We show that the naive generalization has serious problems and we identify the source of the difficulty. We provide a proper generalization of these theories to finite temperature based on a relativistic description of thermal field theories, both in the real and the imaginary time formalisms. Various issues associated with scalar and fermion theories, such as nonanalyticity of self-energy, tensor decomposition are discussed in detail.

Taking as the starting point a perturbative study of the classical equations of motion of the non-Abelian Chern-Simons theory with nondynamical sources, we obtain analytical expressions for link invariants. In order to present these expressions in a manifestly diffeomorphism-invariant form, we introduce a set of differential forms associated with submanifolds in $R^3$ that are metric independent, and that allow us to consider the link invariants as a kind of surface-dependent diffeomorphism invariant that presents a certain Abelian gauge symmetry.

A family of spherically symmetric, static and self-dual Lorentzian wormholes is obtained in n-dimensional Einstein gravity. This class of solutions includes the n-dimensional versions of the Schwarzschild black hole and the spatial-Schwarzschild traversable wormhole. Using isotropic coordinates we study the geometrical structure of the solution, and delineate the domains of the free parameters for which wormhole, naked singular geometries and the Schwarzschild black hole are obtained. It is shown that, in the lower dimensional Einstein gravity without a cosmological constant, we cannot have self-dual Lorentzian wormholes.