By computing anomalous dimensions of gauge invariant composite operators (ψ¯ψ${)}^{\mathit{n}}$ and (${\mathrm{\phi }}^{\mathrm{*}}$φ${)}^{\mathit{n}}$ in matter–Chern-Simons models, we address the fact that the Chern-Simons interactions make these operators more relevant, or less irrelevant, in the low energy region. We suggest a critical Chern-Simons fermion coupling, 1/${\mathrm{\kappa }}_{\mathit{c}}^2$=6/19, for a phase transition at which the leading irrelevant operator (ψ¯ψ${)}^2$ becomes marginal, and a critical Chern-Simons boson coupling, 1/${\mathrm{\kappa }}_{\mathit{c}}^2$=6/34, for a similar phase transition for the leading irrelevant operator (${\mathrm{\phi }}^{\mathrm{*}}$φ${)}^4$. We see the phenomenon also in the 1/N expansion.

Physical consequences in a scenario of an elementary Higgs boson with a mass between 0.6 and 1 TeV together with the presence of comparable heavy fermions are studied. There could be a problem with the S parameter due to the presence of a low-energy P-wave resonance in ${\mathit{W}}_{\mathit{L}}$${\mathit{W}}_{\mathit{L}}$ scattering.

The branching ratio (B) for η→${\mathrm{\mu }}^{+}$${\mathrm{\mu }}^{\mathrm{-}}$ has been measured at the SATURNE tagged-η facility using the reaction pd${\to }^3$He η as a source of ∼${10}^8$ tagged η’s per day. A sample of 100 η→${\mathrm{\mu }}^{+}$${\mathrm{\mu }}^{\mathrm{-}}$ decays on a background of 8 events yield B(η→${\mathrm{\mu }}^{+}$${\mathrm{\mu }}^{\mathrm{-}}$) =[5.$6_{\mathrm{-}0.7}^{+0.6\mathrm{}}$(stat)±0.5(syst)]×${10}^{\mathrm{-}6}$. This value is 1.3±0.2 times the unitarity (lower) bound of 4.3×${10}^{\mathrm{-}6}$, in agreement with most quark and vector meson dominance model predictions.

The scattering of hadrons at high energies can be described by a distribution function of cross sections, which incorporates the phenomena of color transparency and color opacity. We infer here a cross-section distribution for pionic projectiles on nucleons consistent with the data on the moments of the distribution. Using this distribution we calculate the probability for a pion to be in a pointlike configuration and compare with predictions based on a combination of perturbative QCD and QCD sum rules. Comparison with the corresponding distribution for nucleon-nucleon scattering shows that color transparency effects should be more pronounced for a meson beam.

The polarization of 103 211 ${\mathrm{\Omega }}^{\mathrm{-}}$ hyperons produced in 800 GeV proton-beryllium inclusive reactions has been measured. Between 0.3<${\mathit{x}}_{\mathit{F}}$<0.7 and 0.5<${\mathit{p}}_{\mathit{t}}$<1.3 GeV/c, the ${\mathrm{\Omega }}^{\mathrm{-}}$ polarization is found to be consistent with zero, with a mean value of -0.01±0.01 at 〈${\mathit{x}}_{\mathit{F}}$〉=0.5 and 〈${\mathit{p}}_{\mathit{t}}$〉=0.95 GeV/c. This behavior is similar to that of Λ${\mathrm{¯}}^0$, which also does not have any quarks in common with the incident proton, but is different from Ξ${\mathrm{¯}}^{+}$, which is significantly polarized in the same kinematic region.

We present results from an experimental study of reabsorption effects in subthreshold ${\mathrm{\pi }}^0$ production in the reaction ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$${+}^{197}$Au at 44 MeV/nucleon. Within the picture of pion generation in nucleon-nucleon scattering we deduce, from our data and from a comparison with the systematics of production cross sections available for lighter reaction systems, information on the ${\mathrm{\pi }}^0$ absorption length in nuclear matter. For the ${\mathrm{\pi }}^0$ kinetic-energy range ≃5–100 MeV the energy-averaged ${\lambda }_{\mathrm{abs}}$ and its momentum dependence are obtained, and compared with optical-model calculations.

We have developed a technique for producing ultracold beams of ground state ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ atoms by evaporation from a film at subkelvin temperature in a dilution refrigerator. Our analysis shows that we have cooled atoms to below 700 μK and that the cooling process can be continued to below 100 μK. This new technique has great promise for determining the He-He interaction potential to high precision and searching for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ dimer formation. It might also be used to study quantum reflection off surfaces and to search for Bose-Einstein condensation in a dilute gas of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$.

By calculating the two-time correlation function of a one-photon micromaser, we study the line shapes and linewidth of the micromaser spectrum. We find that the half-width at half maximum of the spectrum can be less than the smallest decay rate of the off-diagonal density-matrix elements ${\mathrm{\rho }}_{\mathit{n},}$${\mathit{n}}_{+1\mathrm{}}$, that a hole can appear in the spectrum, and that the spectrum can be split by shifted spectral components.

We provide a sum rule for the length spectrum of pseudointegrable systems in terms of the quantal energies. Further, we derive an expression for the form factor and infer the dependence of spectral fluctuations on the geometry of the system. Our analysis allows us to explain various numerical results obtained in recent years.

A beam propagating in a planar waveguide exhibits the characteristics of both a fundamental soliton (little change in waist of a 5-μm beam; diffraction is compensated by self-focusing nonlinear refraction) and a second-order soliton (10-μm beam focuses to 3 μm with side peaks). These one-dimensional spatial solitons are quite stable; bifurcations of transverse solitary waves are not seen, in sharp contrast with the case for two transverse dimensions. Plasma-theory planar-wave beam-propagation computations agree well with the data and resemble Kerr-medium solitons quite closely.

A Ka-band gyrotron backward-wave oscillator (gyro-BWO) experiment has been performed to investigate the phase control, fast tunability, and power capability. Efficient injection locking was accomplished by novel circuit arrangements. Maximum power of 113 kW at ∼19% efficiency was achieved, showing favorable scaling to still higher powers. Stable voltage tuning bandwidth of 5% at 67 kW peak power was also observed. The measured performance has demonstrated a strong potential of the gyro-BWO for new applications requiring high-power tunable millimeter-wave sources.

The waveguide operation of a compact free-electron laser driven by a 2.3-MeV S-band microtron is reported. Power up to 1 kW in 4-μs pulses has been generated at wavelengths in the range between 2.1 and 2.6 mm. Novel tuning features and temporal characteristics of the emitted radiation, related to the bunched nature of the electron beam and to the dispersive effect of the waveguide, have been observed.

The transverse dynamics of a nonrelativistic, mismatched charged-particle beam propagating through a continuous, linear focusing channel is calculated using the Fokkker-Planck equation to represent the evolution of a coarse-grained distribution function in the phase space of a single beam particle. The relaxation rate and diffusion coefficient are determined from a simple model of turbulence resulting from charge redistribution. The solution for the distribution function enables calculation of all transverse beam properties as a function of time, including the halo.

Dimensionally similar discharges and energy confinement of the W7-AS stellarator were investigated. The results presented, as well as other confinement properties of the net-current-free stellarator, are different from what is known from tokamaks. As expected from global scaling laws for stellerator confinement, the local transport coefficients of dimensionally similar discharges show a gyro-Bohm-like parameter dependence.

The magnetic fluctuation spectrum in a magnetoplasma containing energetic electrons is observed to exhibit many lines at the cyclotron harmonics (ω=n${\mathrm{\omega }}_{\mathit{c}\mathit{e}}$, n=1. . .15). It is shown that these fluctuations are neither due to cyclotron radiation nor due to velocity-space instabilities but due to coherent solenoidal fields produced by electron cyclotron orbits and excited by thermal fluctuations. Such line spectra, observed in discharges and beam-plasma systems, may be useful for precise magnetic field diagnostics in plasmas.

Experiments are presented that demonstrate the process leading to isotropization of the radiation field in a cavity heated by thermal x rays. Gold, cylindrical cavities 500 μm in diameter were heated from one side by ≃154 eV thermal radiation from a laser plasma. The effect of the reemission in transporting energy along the cylinder axis was ascertained by comparing the axial temperature profile of ‘‘open’’ and ‘‘closed’’ geometry targets. The results are in good agreement with a theoretical model for the redistribution of energy via absorption and re-emission of thermal radiation.

We show that diffraction measurements can reach the precision needed to test different models of interatomic interaction also in a dense fluid. Our measurements have been performed in krypton at several temperatures and densities in the liquid phase. Our theoretical calculations show that the density derivative of the static structure, contrary to the function itself, is sensitive to the shape of the interaction and the comparison with the experimental data gives another test of the interaction models.

By studying the finite length scaling of a self-interacting partially directed self-avoiding walk we have verified a new scaling form for the collapsed phase of self-avoiding-walk problems. We suggest therefore that this should hold in polymer systems.

Light scattering was used to study ${\mathrm{N}}_2$ confined in aerogel. We find evidence of liquid-vapor phase separation that terminates at a critical point. Whereas the width of the coexistence curves is substantialy reduced relative to bulk ${\mathrm{N}}_2$, the shape of the coexistence curve is similar to that found for the bulk. Photon correlation spectroscopy shows that the density fluctuations decay algebraically in time, a result consistent with the random-field Ising model.

X-ray scattering and surface tension measurements reveal the formation of a crystalline monolayer on the surface of liquid n-alkanes at about 3 °C above the bulk solidification temperature. The molecules in the monolayer are hexagonally packed and oriented normal to the surface. The single solid monolayer persists down to the bulk solidification temperature, thus exhibiting a very limited partial wetting.