Muonless events from the prompt-neutrino experiment at Fermilab have been analyzed to set limits on the masses and decays of supersymmetric particles by means of three measurements: (1) the $\frac{{\nu }_e}{{\nu }_{\mu }}$ ratio, (2) the rate of events consisting of electromagnetic showers only, and (3) the event rate at large transverse momentum. These limits are based upon the absence of events above our visible energy cutoff of 20 GeV which could be attributed to supersymmetry. Several hypotheses concerning supersymmetric particle decays are considered.

We propose the use of Monte Carlo simulations of QCD to evaluate hadronic matrix elements of local operators encountered in electroweak and grand-unified-theory transitions. Preliminary Monte Carlo estimates are made of the $\Delta S=2\mathrm{}$ matrix elements responsible for the $K_L-K_S$ mass difference and the $\Delta S=1\mathrm{}$ operators believed to explain the $\Delta I=\frac{1}{2}$ enhancement.

We have calculated the excitation energies of projectile fragments produced when relativistic projectiles make peripheral collisions with target nuclei. We find that the excitation energy of the fragment is much greater when the target nucleus is relatively heavy (such as Ag or Br) than when it is light (C or O). This could explain the difference between the results of anomalon searches in nuclear emulsion and plastic detectors.

The tensor analyzing power $T_{20}\left(\theta \right)$ of the reaction ${}_{}{}^2{}_{}{}^{}\mathrm{H}(d,\gamma ){}_{}{}^4{}_{}{}^{}\mathrm{He}$ has been measured at six angles at $E_d=9.7\mathrm{}$ MeV. The result is found to be isotropic with a value of $T_{20}=-0.22\mathrm{}\pm 0.014$. This analyzing power arises from the interference of $S=0\mathrm{}$ and $S=2\mathrm{}$ capture amplitudes. Since the reaction proceeds predominantly via $E2\mathrm{}$ radiation, the $S=2\mathrm{}$ capture strength can be attributed to $S=2\mathrm{}$, $L=2\mathrm{}$ ground-state admixtures. A heuristic model calculation has been used to show that a 4.8% $D$-state admixture in the two-deuteron wave function describing ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ can account for the observed $T_{20}$.

The $K$-shell ionization probability $P_K$ of the uraniumlike products has been measured in the deep-inelastic reaction U + U at a beam energy of 7.5 MeV/u as a function of the total kinetic energy loss $-Q$. $P_K$ was determined for $Q$ values down to - 190 MeV. After the subtraction of the ionization induced by internal conversion of $\gamma$ rays, a strongly $Q$- dependent $P_K$ is found in qualitative agreement with theoretical predictions. From the data we infer a nuclear reaction time of approximately ${10}^{-21\mathrm{}}$ s at $Q=-100\mathrm{}$ MeV.

We present experiments which study velocity-changing collisions for ${}_{}{}^{174}{}_{}{}^{}\mathrm{Yb}$ ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ atomic multipoles. New laser polarization-rotation-transient techniques are used to select anisotropic moments for which the velocity-changing collision kernel is diagonal. The results are compared to those obtained for the collisional evolution of the state populations, and demonstrate that wave mechanical effects play an important role in anisotropic-moment scattering.

The dramatic narrowing of ac Stark-broadened lines in multiphoton ionization spectra is quantitatively explained as a collective and quantum-interference effect.

Instabilities in a nonlinear Fabry-Perot resonator and in an equivalent nonlinear ring resonator with two component cavities are studied. A competition between the time-delayed feedbacks causes a "frustration" in selecting an oscillation mode. The oscillation frequency jumps discontinuously and at random as the ratio of delay times is varied. A number-theoretic method has been successfully applied to elucidate the characteristics of oscillation.

The two-plasmon decay instability in a C${\mathrm{O}}_2$-laser-irradiated gas-target plasma is investigated by picosecond-time-resolved Thomson scattering of ruby laser light. Measured growth rates and their wave-number spectrum agree with theoretical predictions. The instability is saturated by coupling to ion-acoustic fluctuations and is quenched by radial profile modification.

Statistical equilibrium states of a two-dimensional guiding-center plasma are described by the solutions of a nonlinear elliptic partial differential equation, the sinh-Poisson equation ${\nabla }^2\Phi +{\lambda }^{2}sinh\Phi =0\mathrm{}$, with conducting rectangular boundary. We present here the first general analytic solutions to such a nonlinear boundary-value problem. Some of these solutions were obtained previously only through numerical means. Explicit construction of the solutions shows nonlinear superposition among the solutions.

We present the first absolute, two-dimensionally resolved measurements of areal mass density of laser-driven ablatively accelerated foils, which show the Rayleigh-Taylor instability developing from initial mass perturbations. Our data are near simulation results which predict that the Rayleigh-Taylor growth rate is less than classical. The measurements sometimes show development of significant areal mass inhomogeneity in a direction perpendicular to that of the initially imposed perturbations.

The transport properties of strange attractors are studied with the help of a grasshopper's walk which jumps randomly over points separated by a distance $a\pm \delta a$ on the attractor. It is found that the rms displacement of the walk, ${\bar{R}}_w$, is related to the number of steps, $n_w$, through ${\bar{R}}_w^{d_w}\sim n_w$, from which the dimension $d_w$ of the walk is obtained. The values $d_w$ turn out to be nearly the same for all the attractors being studied. This may indicate a kind of "superuniversality" in the transport properties of strange attractors.

We obtain a series of incoherent-inelastic-neutron-scattering spectra covering the complete frequency range of vibrations of hydrogen atoms in water over a temperature range of -15 to 80°C and also in ice at 20 K for reference. Comparison of these frequency spectra with those generated by computer molecular dynamics with flexible water molecules indicates that the proton motion in a free water molecule is substantially affected by formation of hydrogen bonds in the condensed phases.

The formation of Co dimers is observed in a Mössbauer-spectroscopy study of the thermal annealing of Co-implanted Si. The amount of dimers is found to depend strongly on the annealing temperature, on the implantation dose, and on the Si doping. At measuring temperatures between 4 and 300 K electronic relaxation effects are observed.

The resistivity of two types of lithium fast-ion conductors, ${\mathrm{Li}}_{16-2x}{\mathrm{Zn}}_x{\left(\mathrm{Ge}{\mathrm{O}}_4\right)}_4$ ($x=1,2\mathrm{}$) and ${\mathrm{Li}}_{3+x}{\mathrm{Ge}}_x{\mathrm{V}}_{1-x}{\mathrm{O}}_4$ ($x=0.25,0.6,0.72\mathrm{}$), showed pronounced maxima as a function of pressure. For the first type, $\ln \left(\frac{\rho }{{\rho }_0}\right)$ peaked at values of $0.12 \mathrm{}(x=1\mathrm{})\mathrm{}$ and $0.35 \mathrm{}(x=2\mathrm{})\mathrm{}$ near 20 kbar and decreased thereafter up to 80 kbar. Thermal activation energies and prefactors also showed corresponding maxima. For the second type, $\ln \left(\frac{\rho }{{\rho }_0}\right)$ increased to 3-4 between 20 and 32 kbar. Near 80 kbar, $\rho$ decreased (for $x=0.25\mathrm{}$) by a factor of 250. The results are interpreted in terms of negative activation volumes.

Pulsed-ion techniques are used in a 1-cm × 2.3-cm channel to obtain the first spatially resolved measurements of the vortex-line length-density distribution and the normal-fluid velocity field in turbulent counterflow. Also, an upper limit to the structural anisotropy of the vortex tangle is obtained which contradicts earlier claims.

We present computer simulation results supporting the mean-field nature of the exponent for the adsorption in the approach to complete wetting of a system with short-range forces. The limiting logarithmic behavior is found to persist far from coexistence.

A general relation between the critical specific heat above and below a second-order phase transition is derived. It is expressed in terms of the effective four-point coupling $u\left(l\right)\mathrm{}$ of the Ginzburg-Landau Hamiltonian and is valid in the entire region between asymptotic criticality and noncritical background behavior. Application to the $\lambda$ transition of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ yields excellent agreement with the fixed-point value $u^{*}=u\left(0\right)\mathrm{}$ predicted by high-order perturbation theory.

The fractal dimension, $D$, of branched silica polymers is measured by small-angle x-ray scattering. $D$ is independent of branching ratio and does not change during the course of polymerization to a gel.

We report the observation of chaotic ac response in the charge-density-wave state of ${\left(\mathrm{T}\mathrm{a}{\mathrm{Se}}_4\right)}_2$I, when coupled to an external inductance and driven by an rf electric field. The chaotic state is achieved, within a well-defined driving frequency window, by increasing rf amplitude. We analyze our results in terms of a simple nonlinear classical equation of motion for the charge-density-wave condensate.