A new particle, the cosmion, has been proposed to be the dark matter of the Universe and to explain the solar ν deficit by cooling the solar core to reduce ${}_{}{}^8{}_{}{}^{}\mathrm{B}$ ν production. Such cosmions in the galactic halo would scatter from nuclei in terrestrial detectors. Measurements were made in Si ionization detectors in a very-low-background environment down to energies of 1.1 keV. These results exclude nearly all of the mass range possible for cosmions with coherent nuclear interactions.

We present a study of the radiative decay J/ψ→γφφ in the γ${\mathit{K}}^{+}$${\mathit{K}}^{\mathrm{-}}$${\mathit{K}}^{+}$${\mathit{K}}^{\mathrm{-}}$ and γ${\mathit{K}}^{+}$${\mathit{K}}^{\mathrm{-}}$${\mathit{K}}_{\mathit{S}}^0$${\mathit{K}}_{\mathit{L}}^0$ final states. A pseudoscalar state is observed in the φφ invariant-mass spectrum at 2.22 GeV/${\mathit{c}}^2$ with a width of 150 MeV/${\mathit{c}}^2$. The product branching ratios are B(J/ψ→γX)B(X→φφ)=(3.3±0.8±0.5)×${10}^{\mathrm{-}4}$ for the γ${\mathit{K}}^{+}$${\mathit{K}}^{\mathrm{-}}$${\mathit{K}}^{+}$${\mathit{K}}^{\mathrm{-}}$ mode and B(J/ψ→γX)B(X→φφ)=(2.7±0.6 ±0.6)×${10}^{\mathrm{-}4}$ for the γ${\mathit{K}}^{+}$${\mathit{K}}^{\mathrm{-}}$${\mathit{K}}_{\mathit{S}}^0$${\mathit{K}}_{\mathit{L}}^0$ mode. No evidence for $2^{++}$ states below 2.4 GeV/${\mathit{c}}^2$ is found in this radiative J/ψ decay mode.

We use recent measurements of the W- and Z-boson masses and the leptonic, hadronic, and total Z widths to constrain the top-quark mass in the standard model, including full radiative corrections. From a maximum-likelihood analysis we find the most likely value of ${\mathit{m}}_{\mathit{t}}$ to be 151 GeV and we obtain the bound ${\mathit{m}}_{\mathit{t}}$≤200 GeV at 95% C.L. based on the central measured value of the Z mass assuming a Higgs-boson mass of 100 GeV and ${\mathrm{\alpha }}_{\mathit{s}}$(${\mathit{M}}_{\mathit{Z}}^2$)=0.12.

Comparisons of antiproton and proton cyclotron frequencies yield the ratio of inertial masses M(p¯)/M(p)=0.999 999 977 ±0.000 000 042. The fractional uncertainty of 4×${10}^{\mathrm{-}8}$ is 1000 times more accurate than previous measurements of this ratio using exotic atoms and is the most precise test of CPT invariance with baryons. Independent comparisons to electrons yield the mass ratios M(p¯)/M(${\mathit{e}}^{\mathrm{-}}$)=1836.152 660±0.000 083 and M(p)/M(${\mathit{e}}^{\mathrm{-}}$) =1836.152 680±0.000 088. Cryogenic antiprotons (near 4 K) stored in a Penning trap for 2 months establish directly a lifetime greater than 3.4 months.

Using a neural-network classifier we are able to separate gluon from quark jets originating from Monte Carlo–generated ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ events with 85%–90% accuracy.

We describe a full nonspurious 4ħω shell-model calculation that successfully reproduces the low-lying spectrum of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, including the superdeformed $0^{+}$ (6.05 MeV) state, and discuss its connection with the coexistence model. This treatment provides a realistic microscopic framework for discussing various electroweak processes: E2 transitions in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, the role of exchange currents and the pseudoscalar coupling constant in the $0^{+}$⇆$0^{\mathrm{-}}$ β-decay and μ-capture transition, and the evaluation of the Gamow-Teller inclusive response function.

A formalism is developed that incorporates parity violation into the statistical theory of nuclear reactions. It allows the calculation of average square values of observables sensitive to parity breaking starting from well known average parameters (transmission coefficients and level densities) as input. For the case of low-energy neutron resonance scattering, a systematic study of the expected size of the effect is presented. An enhanced sensitivity of these reactions to parity violation is borne out.

Optical isotope shifts have been measured in the 5s[3/2${]}_2^0$-5p[3/2${]}_2$ transition in atomic krypton (λ=760 nm) using collinear-fast-beam laser spectroscopy. Isotope shifts were determined for the short-lived neutron-rich isotopes ${}_{}{}^{88}{}_{}{}^{}\mathrm{Kr}$ and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Kr}$, as well as for all the stable isotopes between A=78 and 86, thus extending the data in this element, for the first time, beyond the N=50 shell closure. The deduced changes in the nuclear charge radii show a decrease of the charge radius with increasing neutron number below N=50, and a much more rapid increase above it. A preliminary interpretation of the results is given in terms of the droplet model.

Photodetachment from negative chlorine ions has been studied in the presence of a strong microwave field. Detachment near the single-photon threshold at 3.613 eV was observed by measuring the production of neutrals resulting from illumination of the ions by pulsed ultraviolet laser light and without microwaves. Microwaves with a frequenty of 2.6 GHz and maximum field strengths near 3 kV/cm produced results consistent with the assumption that each photodetachment event takes place in a constant electric field. No ponderomotive shift in the threshold was evident.

We report the first observation of coherent polarization interactions in dense media in time-resolved degenerate four-wave mixing in semiconductors. For near-resonant ultrashort-optical-pulse excitation, these interactions lead to a diffracted signal at negative delay times, with a slope half that for positive delay times. At higher intensities, two temporal maxima appear in the diffracted signal, in agreement with many-body theory.

A focused beam of 700-eV positrons is used to form orthopositronium (o-Ps) in evacuated, MgO-lined cavities of different sizes. The o-Ps decay rate ${\lambda }_{\mathit{T}}$ is determined to be 7.0482±0.0016 μ${\mathrm{s}}^{\mathrm{-}1}$ after extrapolation to infinite cavity size. This 230-ppm result is 4 times more accurate than previous measurements utilizing the vacuum technique. Subject to radically different systematic effects, it corroborates at the 6.2σ level the discrepancy between theory and a recent 200-ppm measurement of ${\lambda }_{\mathit{T}}$ in gases.

Pairs of 826.8-nm correlated photons, generated by parametrically down-converting 413.4-nm krypton-ion laser light, are directed into a single Mach-Zehnder interferometer such that each photon of the pair enters a different input port. The rate of coincidence at the two output ports displays oscillations (as the path-length difference is swept) with a spatial period equal to the 413-nm wavelength of the pump photons, and with a visibility of 62% when the path-length difference exceeds the coherence length of the individual photon beams. This unequivocally demonstrates the nonclassical and entangled nature of the two-photon state.

At equilibrium, Bloch walls are chiral interfaces between domains with different magnetization. Far from equilibrium, a set of forced oscillators can exhibit walls between states with different phases. In this Letter, we show that when these walls become chiral, they move with a velocity simply related to their chirality. This surprising behavior is a straightforward consequence of nonvariational effects, which are typical of nonequilibrium systems.

The Kolmogorov argument for the existence of an inertial range is reexamined in situations for which neither Fourier modes nor homogeneity and local isotropy are natural assumptions. Scaling arguments are shown which are still valid, and generalizations to the -5/3 law are given for the eigenvalue spectrum of the two-point velocity-correlation matrix. Results from several different numerical simulations are presented. Data derived from simulations of channel and convection flows show that a sensible inertial range appears at very modest Reynolds numbers.

The spectral density of temperature fluctuations in an anisotropic heated turbulent channel flow is studied experimentally using a new optical technique. The spectrum in the direction transverse to the flow shows an equilibrium subrange behavior characteristic of isotropic flows with a wavenumber dependence of ${\mathrm{\Phi }}_{\mathrm{\theta }}$(${\mathrm{\kappa }}_{\mathit{y}}$)∼${\mathrm{\kappa }}_{\mathit{y}}^{\mathrm{-}11/3}$, whereas in the flow direction, ${\mathrm{\Phi }}_{\mathrm{\theta }}$(${\mathrm{\kappa }}_{\mathit{x}}$)∼${\mathrm{\kappa }}_{\mathit{x}}^{\mathrm{-}9/3}$. This difference is shown to result from the dominance of the mean strain rate over the turbulent strain rate field at low wave numbers, and the observed slopes are explained on dimensional grounds.

The structure of the edge radial electric field ${\mathit{E}}_{\mathit{r}}$ inferred from the poloidal rotation velocity is compared with that of the particle and thermal transport barrier for H-mode plasmas in JFT-2M. Both ${\mathit{E}}_{\mathit{r}}$ and its gradient ∂${\mathit{E}}_{\mathit{r}}$/∂r in the thermal transport barrier are found to become more negative at the L-H transition. On the other hand, ∂${\mathit{E}}_{\mathit{r}}$/∂r is more positive outside of the separatrix. The shear of the radial electric field and poloidal rotation velocity in the H mode is localized within the order of an ion poloidal gyroradius near the separatrix, in the region of ion collisionality ${\nu }_{\mathrm{*}\mathit{i}}$≊20–40.

Propagation of second sound has been used to study superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He mixtures quenched into nonequilibrium states inside the miscibility gap. From the results for the second-sound velocity we conclude that the superfluid density in the metastable state is well described by extrapolation from equilibrium values. The attenuation of the second-sound amplitude displays a sharp increase as nucleation sets in at the cloud point, and during the subsequent coarse-graining process it varies in proportion to the total surface area of the droplets.

We study the phase separation of the O/W(110)-p(2×1)+p(2×2) system with LEED as it is quenched from an ‘‘infinite’’-temperature initial state to within its coexistence region. Novel features of this system are the fourfold degeneracy of the ordered phases and their finite densities. The measured growth exponent is consistent with the Lifshitz-Slyozov prediction x=1/3. Diffusion activation energies measured with two independent methods are consistent with each other and lead to E≊0.58 eV.

We present a many-body WKB description of the tunneling of a single electron from the surface of liquid helium. Accurate upper and lower bounds show conclusively that the observed temperature-independent rate cannot be tunneling.

The one-band Hubbard model is considered in the slave-boson formulation first introduced by Kotliar and Ruckenstein. It is shown that a mean-field approximation, where broken-symmetry states appropriate for a bipartite lattice are allowed, leads to a quantitative agreement with quantum Monte Carlo results for local observables over a wide range of interactions (0<U≤20t) and doping (0<〈n〉≤1). Thus, our saddle-point solutions constitute an excellent starting point for a systematic treatment of fluctuations.