We have looked for γ-ray emission above 100 TeV from the binary x-ray source Cygnus X-3 during a period of intense radio emission in the summer of 1989. We find no evidence for excess air showers from the direction of the source and the muon content of air showers from this direction is the same as that of ordinary cosmic rays. The flux of γ rays from Cygnus X-3 with energies exceeding 2.1×${10}^{14}$ eV is <5.5×${10}^{\mathrm{-}13}$ ${\mathrm{cm}}^{\mathrm{-}1}$ ${\sec }^{\mathrm{-}1}$ (90% C.L.).

The neutron electric dipole moment ($d_n$) due to Higgs-boson exchange is reconsidered, now without assuming that Higgs-boson exchange is solely responsible for $K_L^0$→2π. The dominant contribution to $d_n$ arises from a three-gluon operator, produced in integrating out top quarks and neutral Higgs bosons. The estimated results together with current experimental bounds on $d_n$ show, even for the largest plausible Higgs-boson masses, that CP is not maximally violated in neutral-Higgs-boson exchange.

Creation of kink-antikink pairs within the (1+1) dimensional real scalar field theory at finite temperature is considered as a result of the real-time evolution of a Hamiltonian system which interacts with a thermal bath. The relevant Langevin equation is solved numerically on the lattice, and both the density of kinks and the pair-creation time are obtained as functions of the temperature. We find that the effective kink mass is reduced at high temperatures. This observation may be important for the evaluation of the cosmological production of monopoles.

Using 123 multihadronic inclusive muon-production $e^{+}$$e^{\mathrm{-}}$ annihilation events at an average c.m. energy of 55.2 GeV, we extracted the forward-backward charge asymmetry of the $e^{+}$$e^{\mathrm{-}}$→bb¯ process and the R ratio for bb¯ production. We used an analysis method in which the behavior of the c quark and lighter quarks is assumed, with only that of the b quark left indeterminate. The results, $A_b$=-0.72±0.28(stat)±0.13(syst) and $R_b$=0.57±0.16±0.10, are consistent with the standard model.

It is shown that rescattering corrections to γp→${\pi }^0$p through the sequence γp→${\pi }^{+}$n→${\pi }^0$p, at threshold, and to γn→${\pi }^0$n through the sequence γn→${\pi }^{\mathrm{-}}$p→${\pi }^0$n, are large. The cusps at ${\pi }^{+}$n and ${\pi }^{\mathrm{-}}$p thresholds, $k_L$=151.5 and 148.5 MeV, respectively, are inverted. It is also argued that an explanation of the discrepancy between experiment and theory through a Σ-like term is, most likely, erroneous.

Coherent single-pion production on neon nuclei is studied using the Fermilab 15-ft bubble chamber filled with a heavy Ne-${\mathrm{H}}_2$ mixture and exposed to the Tevatron neutrino beam. In the neutrino energy range 40–300 GeV, the net signal is 20±6 events, giving a corrected rate per charged-current event of (0.26±0.10)%. The cross section and kinematic distributions agree with the predictions of a model based on partial conservation of axial-vector current and meson dominance.

The reaction ${\pi }^{\mathrm{-}}$${+}^3$He→η+t has been observed by detecting η→2γ decays. The observed forward-angle cross sections vary from ∼100 μb/sr at 680 MeV/c to ∼2 μb/sr at 590 MeV/c. Distorted-wave impulse-approximation calculations reproduce the shape but underestimate the magnitude of the observed cross section. These cross sections are approximately 100 times larger than those for the reaction p+d→η${+}^3$He measured at similar η center-of-mass energies.

We study the frequency lockings of two intrinsic hydrodynamic modes of a convecting ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He mixture by independently varying the Rayleigh and Prandtl numbers. We establish points on the critical line in this parameter space using a transient technique to locate the spiral-node transition in the interior of three resonance horns. Universal scaling is demonstrated at winding numbers with golden mean tails by computing the f(α) singularity spectrum.

Power dissipation mechanisms in low-pressure helium radio-frequency glow discharges are studied using a model which is able to describe the discharge at the kinetic level with a self-consistent electric field. We find a low average electron energy (<1 eV) in the bulk plasma and a weak electric field (≊2 V/cm) that is largely out of phase with the sheath fields. The weak bulk field is shown to be important for heating electrons of all energies.

A sharp transport barrier, accompanied by a bifurcated poloidal rotation and a radial electric field, is formed at the plasma edge by driving a radial current across the outer magnetic surfaces of a tokamak. A decrease in particle transport is observed for negative radial E fields. When the radial current is turned off, the E field and the rotation damp on a time scale comparable with the ion-ion collision time.

It is shown that the poloidal momentum balance equation in tokamaks has bifurcated solutions. The poloidal flow velocity $U_p$ can suddenly become more positive when the ion collisionality decreases. The corresponding radial electric field $E_r$ becomes more negative and hence suppresses the turbulent fluctuations. Thus, plasma confinement is improved. The theory is employed to explain the L-H transition observed in tokamaks.

Dilute suspensions of micron diameter dielectric spheres confined to two dimensions are induced to aggregate linearly by application of an electric field. The growth of the average cluster size agrees well with the Smoluchowski equation, but the evolution of the measured cluster size distribution exhibits significant departures from theory at large times due to the formation of long linear clusters which effectively partition space into isolated one-dimensional strips.

The evolution of cells and dendrites on a solidification front is analyzed numerically by a Green’s-function method. We obtain a consistent picture of the pattern-forming processes in the whole experimentally accessible range of the phase-diagram cell spacing versus growth rate. We find a smooth transition from cells to free dendrites confirming suspected scaling relations. The selection of dendritic spacings appears to occur through a tail instability.

Inelastic-neutron-scattering studies of glassy, liquid, and polycrystalline selenium have been performed at temperatures between 100 and 600 K. A self-consistent data evaluation, taking careful account of multiple and multiphonon scattering, shows that a complete interpretation is possible in terms of a temperature-dependent density of vibrational states, together with diffusion broadening of the elastic line. This density of states is used to calculate thermodynamic properties and to show that about one-third of the additional entropy of the liquid is vibrational. The results raise a number of questions concerning current theories of the glass transition.

Polariton decay rates have been directly measured for the first time in the subpicosecond time domain through an application of time-resolved anti-Stokes Raman scattering. Two decay rates are observed in GaP. The temperature dependence of the decay rates leads to the identification of the two decay channels. These results expand those previously obtained in the spectral domain and illustrate the advantages of investigations in the time domain.

In situ x-ray scattering has been used to study a growing film (ZnSe on GaAs) during organometallic vapor phase epitaxy. This first in situ study of non-ultrahigh-vacuum growth revealed a surprisingly stable and well-ordered p(2×1) reconstruction during growth despite the presence of organic-reaction by-products. Also, dramatic changes in the specular x-ray reflectivity were found while investigating transient kinetic effects during alternate source epitaxy. These results demonstrate the power of in situ x-ray-scattering studies in the characterization of these complex processes.

Scanning-tunneling-microscopy measurements of submonolayer growth of Si on Si(001) show anisotropic island shapes. From coarsening experiments it is determined that these shapes are a consequence of the growth kinetics. They can be explained by a lateral accommodation coefficient for atoms arriving at the edge of islands that differs by an order of magnitude at the ends and at the sides of dimer rows.

We demonstrate for the first time the well-defined dispersive character of optical phonons in III-V mixed crystals. Raman scattering on short period GaAlAs/AlAs superlattices evidences several modes confined in the alloy layers. This determines experimental points on the bulk-alloy phonon dispersion curves in agreement with the predictions of a coherent potential approximation calculation which takes into account both disorder and superlattice effects.

Electronic states in conducting polymers containing impurities are analyzed. The influence of backward and forward scattering (bond and site) impurities is studied using the coherent potential approximation. Because of the 1D nature of the problem, the formation of impurity bands in the gap, as known from different circumstances such as semiconductors and superconductors, is suppressed if strength of the bond impurity is larger than that of the site impurity. Consequences for the interpretation of experiments are discussed.

It has been widely observed in ionic donor-acceptor charge-transfer (CT) compounds that kink-type domain walls between one-dimensional ferroelectric molecular domains show strong dielectric response with a thermally activated relaxation frequency over a wide temperature range. The domain walls can carry spin and electric charge, which produce anomalous charge-transport phenomena observed in this type of CT dielectrics.