The heavy-quarkonium decay ${}_{}{}^3{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}$(QQ¯)→Z+Higgs boson, a feasible process for Higgs-boson searches, is shown to be highly sensitive to the structure of the HQQ¯ vertex. A study of the angular distributions of the Z decay products can distinguish between the scalar or pseudoscalar form of this vertex and provide important information on the electroweak-symmetry-breaking mechanism.

The proton-proton two-body density in the three-nucleon system is extracted from quasielastic-electron-scattering data. The two-body density is determined in momentum space using the integrated longitudinal response functions and assuming that the nonrelativistic Coulomb sum rule is valid. The range of the measurement is for momenta between 200 and 550 MeV/c. The data are compared to a proton-proton density calculated using Faddeev wave functions. The data and the calculation both show a ‘‘second maximum’’ but the data exceed the calculation by about an order of magnitude.

It has been known from some time that the intrinsic state labeled by the asymptotic quantum numbers ${(3/2\mathrm{}}^{+}$[631] lies quite close (<0.1 keV) to the ${(5/2\mathrm{}}^{+}$[633] ground state of ${}_{}{}^{229}{}_{}{}^{}\mathrm{Th}$. Using the energies of selected γ rays emitted following the α decay of ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$, we have obtained a value of 1±4 eV for the energy separation of these two intrinsic states.

Using a novel six-laser excitation scheme we have created heliumlike planetary states (nlNd) in barium with n≥30, N≥60, and l≥4, which are equivalent of a true three-body Coulomb system. Extremely strong positional correlation effects were observed and quantitatively explained by the repulsion between a ‘‘frozen’’ outer electron and the highly polarizable inner electron. The model was experimentally verified by removing the outer electron and recording the inner electron excitation in the presence of an equivalent electric field.

Partial cross sections for the photodetachment of a 2s or 2p electron from metastable (1s2s2p${)}^4$P ${\mathrm{He}}^{\mathrm{-}}$ ions have been determined using crossed-beam photoelectron spectroscopy. Kinematic effects associated with detachment from a fast beam source have been exploited, in a novel way, to enhance the precision of the measurements. Calculated cross sections for the photodetachment of ${\mathrm{H}}^{\mathrm{-}}$ were used to establish a scale for the ${\mathrm{He}}^{\mathrm{-}}$ measurements. Radiative attachment cross sections from the photodetachment results using the principle of detailed balance.

We show that stable localized waves can be generated in the vicinity of an inverted Hopf bifurcation. We compute the size of the localized wave envelope perturbatively in the case of slightly dissipative systems. The size selection traces back to the broken scale invariance by the dissipative terms. This mechanism is a possible explanation for the localized structures, widely observed in various hydrodynamic flows in dissipative systems driven far from equilibrium.

A wave-number-in-cell code was developed for simulation of a model proposed by Vendenov, Gordeev, and Rudakov for studying weak Langmuir turbulence. The model uses a WKB approach for describing the Langmuir wave field. Theoretical results for damping of ion acoustic waves caused by resonant interaction of Langmuir waves with group velocity around the sound speed were confirmed. Simulations corresponding to an initial condition with an intense wave burst demonstrate a formation of almost stationary localized cavities of intense wideband self-trapped Langmuir wave fields. These cavities have features in common with phase-space vortices.

Selected phonon modes in ${\mathrm{Cu}}_3$Au have been studied at temperatures in the vicinity of the order-disorder transition by neutron-scattering techniques. Marked changes occur predominantly at temperatures well below the region of the precipitous drop in the order parameter. Our results give considerable support to the concept of spinodal ordering near a discontinuous phase transition, and are consistent with a lower spinodal temperature of $T_c$-24 K as inferred from earlier x-ray scattering results.

The equations of the smoothening dynamics of a crystal surface below the roughening transition are written in the case of evaporation dynamics. It is assumed that only ledges separating smooth planes are mobile. The equations are applied to the classical experiment in which the decay of parallel grooves is studied. The formation of facets, which has been observed, is argued to be possible only if the average surface makes a small, but nonvanishing angle α with a high-symmetry direction. If α=0, the profile is predicted to have sharp maxima and minima with (4/3 singularities.

A new insight is provided into ring-exchange processes occurring in two-dimensional solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ layers adsorbed on grafoil. Three-particle exchange dominates at high and moderate areal density leading to the ferromagnetic properties previously observed. At the low densities corresponding to the observation of commensurate phases, higher-order antiferromagnetic four- and six-spin exchanges are relatively more important and lead to a frustrated antiferromagnetic system. A variety of anomalies recently observed are explained in a unified way.

Utilizing an optical holographic setup thick refractive index gratings are written in poly(methyl methacrylate) (PMMA). We show experimentally that these gratings diffract not only visible light but also cold neutrons.

We present a density-functional approach to the freezing of quantum systems which emphasizes the role of the liquid phase. The key ingredient of this theory is the static response function of the homogeneous liquid. From this quantity one constructs the difference of the relevant free energy between the liquid and a given crystalline phase and hence locates the melting curve. As an illustration we study the Wigner crystallization.

The polar interface interaction between a chiral smectic-A liquid crystal and a solid substrate results in an induced ferroelectric polarization and chiral reorientation of the director in the liquid crystal near the surface.

The surface crystallography of epitaxially grown ${\mathrm{YSi}}_{2\mathrm{-}\mathrm{x}}$ (x=0.3 and x=0) films on Si(111) has been investigated using x-ray photoelectron diffraction. For the ${\mathrm{YSi}}_{1.7}$ films, vacancies form an ordered √3 × √3 R30° superlattice within each Si plane. These vacancies are filled for ${\mathrm{YSi}}^2$. The analysis reveals that their surfaces are Si terminated with a displacement upward (0.8 Å) of one Si atom out of two so that they exhibit the same geometry as a 1×1 Si(111) surface.

Spectroscopic ellipsometry of epitaxial Ge in bulk Si(100) has been used to study the effects of strain and layer thickness on the Ge-derived ${\mathrm{E}}_1$ transitions. Although a 4-Å-Ge layer exhibits no Ge-like ${\mathrm{E}}_1$ structure, localized ${\mathrm{E}}_1$-like transitions are observed for 7-Å-Ge layers showing the ${\mathrm{E}}_1$ transition is a robust probe of the Ge-like behavior in ultrathin layers.

A proton NMR study was carried out on the stage-1 potassium-hydrogen-graphite ternary intercalation compound ${\mathrm{C}}_4$${\mathrm{KH}}_{\mathrm{x}}$, prepared through direct intercalation of potassium hydride into graphite. Line-shape analysis revealed extremely dense two-dimensional packing of negatively charged hydride ions where hydrogen-hydrogen direct contact takes place. The metallic nature of hydrogen was observed through the Korringa term, (${\mathrm{T}}_1$T${)}^{\mathrm{-}1}$=6.4×${10}^{\mathrm{-}4}$ ${\mathrm{s}}^{\mathrm{-}1}$ ${\mathrm{K}}^{\mathrm{-}1}$, where ${\mathrm{T}}_1$ is the spin-lattice relaxation time. ${\mathrm{C}}_4$${\mathrm{KH}}_{\mathrm{x}}$ is thus proven to be an example of two-dimensional metallic hydrogen.

The possibility of superconductivity in polymers is studied in one-dimensional models of interacting electrons coupled to acoustic phonons or intramonomer vibrations. For acoustic phonons, the dimerized state is stable and superconductivity does not occur, in disagreement with recent work by Zimanyi, Kivelson, and Luther. For intramonomer vibrations in an incommensurate (highly doped) system, superconductivity strongly competes with charge-density waves and is favored by high phonon frequencies, well screened electronic interactions, and n-type doping.

The coupled-cluster method is widely applicable to quantum systems of interacting particles or fields. Such concepts as supercoherent states, generalized order parameters, and exact mappings onto corresponding multilocal classical field theories arise naturally within it, particularly in its extended version. Its holomorphic representation is applied here to the anharmonic oscillator, in order to demonstrate several key mathematical features.

It is shown that neutrinos (massless or massive), produced with kinetic energies below ∼50 eV in a supernova, have bound orbits in the remnant neutron star. The binding is mediated by a radial weak-interaction force, caused by a gradient in the collective weak potential of the neutrons in the star. This force is also able to create spontaneously neutrino-antineutrino pairs. If the bound-neutrino sphere is not fully degenerate at low momenta, a cold neutron star will shine continuously antineutrinos with energies ≲50 eV, as a result of the density gradient in it. In principle, these effects can also be realized at smaller (e.g., solid) densities for sufficiently low neutrino energies.

A system of intercommuting cosmic strings is numerically evolved in a homogeneous radiation-dominated expanding universe. Further evidence for the existence of a ‘‘scaling’’ solution is presented, and results for the long-string energy density are given. Long strings exhibit significant small-scale structure—kinks and short-wavelength propagating modes. Net loop production is observed to be strongly peaked at scales considerably smaller than the horizon, and reasons for this severe fragmentation are briefly discussed. The new numerical techniques employed are also described.