Coherent production of $K\pi$ systems observed in the excitation of 200-GeV/c positive kaons on nuclear targets has been analyzed, including both electromagnetic and strong contributions, to yield a new value for the radiative width for the process $K^{*+}\mathrm{}\left(890\right)\mathrm{}\to K^{+}\gamma$ of 51 ± 5 keV.

A new formulation of lattice gauge theory with fermionic degrees of freedom is presented and analyzed. Arguments are given which imply that, unlike all previous local prescriptions, the present one allows the implementation of chiral symmetry without leading to the doubling of fermion species. This permits the lattice regularization of theories with handed fermions.

The reported discovery of the $W$ boson may provide the opportunity either to discover the supersymmetric partners of the neutrino and the electron or to set greatly improved limits on their masses. Also discussed is a search for scalar neutrinos in $e^{+}{e}^{-}$ annihilation (off and on the $Z^0$).

Nuclear polarization $P$ of the short-lived $\beta$ emitter ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ was produced by the beam-foil interaction and directly determined via asymmetric $\beta$ decay. For a single tilted foil, at boron energy $E_{\mathrm{B}}=1.0\mathrm{}$ MeV, $\mathrm{}\left|P\right|=1.82\mathrm{}\left(14\right)\%$. This was enhanced to $\mathrm{}\left|P\right|=4.69\mathrm{}\left(46\right)\%$ by stacking four tilted foils. The dependence of $P$ vs $E_{\mathrm{B}}$ was observed for a single tilted foil in the range of $E_{\mathrm{B}}=0.6\mathrm{} \mathrm{to} 1.3$ MeV. The sign of $P$ followed that of the tilt angle and was consistent with predictions from electron-density-gradient models.

The linewidth of the excitation spectrum for multiphoton ionization is found to be broadened much more severely than the cascade fluorescence originating from the resonant intermediate level. These results are due to the mutual effects of the ionizing and resonating transitions, which are not properly accounted for in perturbative treatments.

The first low-temperature (<4 K) determination of the sticking probability $S$ of a ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ atom on a solid surface is presented. It is found that $\frac{2}{3}\lesssim S<\mathrm{}1\mathrm{}$ for a thermal distribution of incident atoms with beam temperature 10 to 20 K. This result is not affected by the presence of a preadsorbed, ≲ 1-monolayer He film.

High-precision heat-capacity and molecular-dynamics-simulation studies on the orientational transition of nitrogen molecules adsorbed on graphite are reported here. The peak in the heat-capacity data is rather narrow and shows no observable finite-size effects. The simulation studies show that, in addition to the loss of orientational order in the plane of the surface, significant reorientation in the direction perpendicular to the surface is also found as temperature is increased.

Periodic spinodal decomposition has been observed in a critical binary mixture of isobutyric acid and water. As predicted by Onuki, phase separation can be dramatically slowed down by a periodic quench of appropriately chosen mean value and amplitude of the temperature variations. Depending on details of the quench conditions, two steady-state conditions can be achieved, in one of which the system has completely separated.

The silicon (111) 7×7 surface reconstruction has been observed by surface-sensitive transmission-electron microscopy. The topography of the reconstructed surface is accounted for by the cooperative motion of surface atoms over large areas via a new process involving the generation of "surface dislocations" to relieve the backbond-induced surface stresses.

A solid-on-solid interface representation of the random-field Ising model is studied numerically in two dimensions. The interface width varies linearly with sample size, in agreement with simple energy-accounting arguments and recent theories which predict that two is the lower critical dimension of the random-field Ising model.

The spin-polarized electronic structure around a positive muon ${\mu }^{+}$ at the tetrahedral interstitial site of silicon is calculated by use of the local spin-density functional formalism and the linear combination of atomic orbitals-Green's function method. A paramagnetic solution is obtained for the first time. The reduction of hyperfine coupling constant, $A$, experienced by ${\mu }^{+}$ at absolute zero temperature is calculated to be 0.406 in good agreement with the experimental value of 0.405±0.026 or 0.450±0.020.

Electron-excited $4d^{10}\to 4d^{9}4f$ transitions in clean La metal and tetravelent Ce${\mathrm{O}}_2$ show systematic deviations from those observed in x-ray absorption. At intermediate primary energies simple selection rules allow a limited range of new singlet excitations, while triplet excitation becomes very prominent as the primary energy approaches threshold. With this technique a complete multiplet analysis of atomiclike core excitations has become possible for the first time.

Measurements of the Hall and the time-of-flight mobilities of electrons injected into neopentane along the liquid-vapor coexistence curve between the triple and the critical points are reported. The ratio of the Hall mobility to time-of-flight mobility always exceeds unity; it decreases linearly from 1.8 at low temperatures to 1.4 near 410 K and increases thereafter to nearly 5.8 in the vicinity of the critical point. This is suggestive of localized states associated with density fluctuations. These density fluctuations are probably the dominant scattering mechanism that determines the Hall mobility.

New exact results are presented on the long-time asymptotic expansions of the $T=0\mathrm{}$ autocorrelation functions, and on the leading singularities of their frequency-dependent Fourier transforms, for the one-dimensional $S=\frac{1}{2}$ isotropic $\mathrm{XY}$ model and the $S=\frac{1}{2}$ transverse Ising model at the critical field. High-precision numerical calculations of the latter functions are also given, and experiments are proposed to observe the functional behaviors that are found.

New calculations of the flux of neutrinos produced by cosmic rays in the atmosphere are reported. The authors have taken account of effects of the geomagnetic cutoff and of solar modulation separately for upward- and downward-going neutrinos of both electron and muon flavor with energies from 200 MeV to 10 GeV. The geomagnetic cutoff in particular must be handled carefully because it induces behavior very similar to a neutrino-oscillation signal.

Simple analytical estimates of the fluxes of atmospheric muons and neutrinos are presented. It is shown that the geomagnetic field strongly suppresses the fluxes of atmospheric neutrinos below 1 GeV from directions of low magnetic latitudes and may open a window for neutrino astronomy. The validity of these estimates is demonstrated through indirect tests.

Quenching of the $M6\mathrm{}$ transition strengths in inelastic scattering to $6^{-}$ states in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ is predicted when the $d_{\frac{5}{2}}$ shell-model space is enlarged to include the $s_{\frac{1}{2}}$ single-particle orbital. Nucleon transfer cross sections to the yrast $\mathrm{}(I,T)=(6^{-},0) \mathrm{and} (6^{-},1)$ states and $B\left(M1\mathrm{}\right)\mathrm{}$ between them are also predicted to decrease when the extended space is used. The calculations suggest that the data may be understood in terms of only nucleon degrees of freedom once an adequate model space is used.

A statistical approach to transfer ionization is used to calculate multiple-ionization probabilities for target ions produced in slow multielectron-capture collisions of multiply charged ions and atoms.

Collisionless multiphoton absorption, resulting in multiple atomic ionization and exhibiting anomalously strong coupling, has been studied in the region spanning atomic number $Z=2\mathrm{}$ (He) to $Z=92\mathrm{}$ (U). The highest ion state identified is ${\mathrm{U}}^{10+}$, corresponding to absorption of 99 quanta (∼633 eV). Models of stepwise ionization using standard theoretical techniques are incapable of describing these results. A mode of interaction involving radiative coupling to a collective motion of an atomic shell is proposed.

The spin relaxation of the positive muon in copper has been measured below 5 K in zero applied magnetic field. The results are well described by the theory of Kubo and Toyabe with a temperature-independent dipolar width. It is concluded that neither trapping nor changes in the muon site with temperature explain the increased mobility below 5 K.