In a supersymmetry scenario with a mass hierarchy ${\mathrm{m}}_{\mathrm{g}\mathrm{̃}}$≊${\mathrm{m}}_{\mathrm{q}\mathrm{̃}}$>${\mathrm{m}}_{\mathrm{\omega }\mathrm{̃}}$>${\mathrm{m}}_{\mathrm{l}\mathrm{̃}}$ , gluino-scalar quark pair production followed by the decay chain g̃→q̃ q¯(q̃¯q), q̃→ω̃q, ω̃→μ̃ν(μν̃), μ̃→μγ̃ leads to like-sign and unlike-sign dimuons with comparable rates and possibly little accompanying hadronic activity; such events will often contain strange particles. Predictions are made for the dimuon distributions. The possible relevance to dimuon observations by Arnison et al. is addressed.

We discuss constraints on the three by three Majorana neutrino mass matrix consistent with neutrinoless double β decay experiments, neutrino oscillation experiments, and the existence of a 17-keV neutrino. We find that ${\nu }_{\mu }$ and ${\nu }_{\tau }$ must be nearly degenerate, or ${\nu }_{\mu }$ must be heavier than 250 keV. A new parametrization of the mixing in the neutrino sector is proposed. We give a simple example of a mass matrix which satisfies all constraints.

The inelasticity distribution and energy loss of leading particles, which are essential ingredients in statistical models for multiparticle production processes and the phase transition from hadronic to quark-gluon matter, have been calculated in an approach in which the dominant role is played by interacting gluons. The interpretation of existing experimental data indicates an appreciable reduction of the number of soft gluons in comparison with that deduced from a naive extrapolation of deep-inelastic–scattering experiments.

Correlations between coincident alpha particles and deuterons emitted in ${}_{}{}^{40}{}_{}{}^{}\mathrm{induced}$ reactions on ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ at E/A=60 MeV were measured. The relative populations of particle-unstable states of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ were extracted. The measured spectra are consistent with a mean nuclear temperature at emission of T=5 MeV. Limitations of temperature measurements via the population of excited states are discussed.

We describe an experiment which has detected light emission from a plastic scintillator due to neutron-induced recoil protons with initial energies as small as 410 eV. The velocity of such protons is smaller than that expected of grand-unified-theory magnetic monopoles. Searches for these exotic particles will therefore not be limited by kinematic or adiabatic constraints at velocities in excess of 9×${10}^{\mathrm{-}4}$c.

Below the ${}_{}{}^{16}{}_{}{}^{}$O${+\mathrm{}}^{16}$O threshold, positive- and negative-parity bands at $E_x$=11–17 MeV in ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ are identified, whose moments of inertia and α-reduced widths indicate possible quasimolecular bands of ${}_{}{}^{16}{}_{}{}^{}$O${+\mathrm{}}^{16}$O and of some asymmetric configuration.

We have observed a striking line narrowing in the photoionization spectrum of sodium atoms in an electric field. At crossings of two relatively broad resonances, one of them is narrowed by 2 to 3 orders of magnitude as a result of interference between the discrete and continuum coupling amplitudes that mediate their ionization. The observations agree quantitatively with WKB quantum-defect Stark theory and also with a simpler model involving two discrete states and two continua.

We have observed the effect of electric fields on the 5d9p ${}^3$$P_1$° barium resonance above the first ionization threshold. This relatively broad autoionizing level is nearly degenerate with a much narrower level of opposite parity. At moderate fields the sharp level produces an interference dip in the broad level. At higher fields the interference eventually gives rise to two split components. The results are in good agreement with a nonperturbative theory, summarized in this letter.

A new component is observed in ∼0° electron cusp spectra produced by megaelectronvolt per nucleon ${\mathrm{H}}^{+}$ or ${\mathrm{He}}^{++}$ bombardment of hydrocarbon molecules with more than three C atoms. This component is narrower than, and different in skew and yield energy dependence from, electron capture or loss to the continuum processes, and has a width that is dependent on projectile Z. Of the presently proposed mechanism for single forward electron production, only wake production in the larger molecules cannot be eliminated, although wake model predictions agree just qualitatively with our experimental results.

Using a mean-field approach we derive the scaling exponents for the molecular weight dependence of the polymer dimensions and critical strain rates in dilute solutions of polymers undergoing a coil-stretching transition in elongational flows. While for Θ solvents our predictions agree with existing theories, a new exponent for the critical strain rate is predicted in the good-solvent case. Our results are in satisfactory agreement with available experimental data.

The finite-amplitude tuning curves of a surface-wave resonator have been determined for various liquid depths. It is found that the direction of the bending of the tuning curve depends on the liquid depth. The free decay rate of the soliton is measured and shows that solitons initially decay much faster than the corresponding transverse mode but have the same rate in the terminal decay.

An experimental study of competing instabilities in a rotating layer of mercury heated from below is reported, and analyzed in the framework of codimension-two bifurcation theory.

A three-dimensional self-organization process in an incompressible dissipative plasma is investigated by means of a magnetohydrodynamic simulation. Two typical phases are observed, i.e., the energy-relaxation phase and the inverse-cascade phase. In the relaxation phase the total magnetic energy rapidly decreases while the magnetic structure is transformed into a simpler one by magnetic reconnection. In the inverse-cascade phase the magnetic helicity spectrum shifts towards the low-wave-number region while the magnetic energy spectrum shifts towards the high-wave-number region.

A theory is developed for the hcp-fcc structural phase transition in close-packed metals as a function of the average electron concentration per atom. It is found that the transition can be continuous at low temperatures. Ordered polytypic stacking sequences are found near the transition point. Short-period structures are stabilized by Fermi-surface effects but long-period structures result from elastic distortion of the lattice. Unusual ‘‘staircase’’ crystallographic data for Mg-based Friauf-Laves alloys are accounted for successfully and the structure of rare-earth intermetallic alloys is discussed.

A nonlinear theory of domain walls in intercalation compunds is presented. Realistic domain-wall energies and barriers to the relative motion of intercalate domains are calculated for the entire range of guest species intercalating into graphite. The different stackings of host layers found in stage-2 compounds are studied. The dependence of the energetics on stacking and intercalate thickness is both unexpected and complex and should profoundly affect the intercalation kinetics. An explanation is proposed for the anomalous behavior of sodium and some other guest species.

Li diffusion in ${\mathrm{LiC}}_6$ has been measured by high-resolution neutron spectroscopy both in the ordered phase between 630 and 675 K and in the disordered phase at 720 K. The in-plane diffusion constant D at 660 K is 1×${10}^{\mathrm{-}6}$ ${\mathrm{cm}}^2$/s, which increases to 24×${10}^{\mathrm{-}6}$ ${\mathrm{cm}}^2$/s above ${\mathrm{T}}_{\mathrm{c}}$. At all temperatures, a jump-type diffusion mechanism was observed, with jump vectors connecting nearest Li-sublattice sites in the ordered phase, but nearest hexagon centers in the disordered phase.

We describe a system where the dynamics of reversible clustering, ordering, and growth in two dimensions can be directly observed. The system consists of uniform colloidal particles trapped at an air/water interface. We attribute the attraction between particles mainly to pairwise potential with a longer-range van der Waals attraction and a shorter-range, electrostatic repulsion. Surface tension may also contribute as the cluster sizes increase. Reversible dynamics result from the combination of these forces with the disrupting influences of Brownian motion.

The tunneling current density is computed in the vacuum region between two planar metal electrodes, on one of which is an adsorbed atom. The calculation uses self-consistent wave functions for each electrode; the effects of adatom valence resonances are fully taken into account. This study leads to a better understanding of important aspects of the current flow in the scanning tunneling microscope. Its emphasis is not so much on the question of resolution discussed in earlier theoretical work, but on the characteristic signatures of chemically different atoms at a surface.

We present the results of magnetic x-ray scattering experiments on the rare-earth metal holmium using synchrotron radiation. Direct high-resolution measurements of the nominally incommensurate magnetic satellite reflections reveal new lock-in behavior which we explain within a simple spin-discommensuration model. As a result of magnetoelastic coupling, the spin-discommensuration array produces additional x-ray diffraction satellites. Their observation further substantiates the model and demonstrates additional advantages of synchrotron radiation for magnetic-structure studies.

A simple theory is developed for hopping diffusion in hard-core lattice gases. Its predictions for the mean square displacement of a tracer particle as a function of time are found to be in good agreement with the results of Monte Carlo simulations on a quadratic lattice. For long times a logarithmic term is found in accord with mode-coupling predictions. Our predictions for the tracer diffusion coefficient agree with those of Tahir-Kheli.