We study the two-point correlations of cosmic-string loops with numerical simulations of the evolution of a cosmic-string network in an expanding universe. We find that the initial positions of loops that are chopped off the network have a correlation function that is quite similar to the highest estimates of the Abell-cluster correlation function, but these correlations are rapidly washed out by the motion of the loops. The implications for the cosmic-string galaxy-formation scenario are briefly discussed.

Recent work suggests that wormholes in spacetime may drive ${\theta }_{\mathrm{QCD}}$ to π, and it has been argued that this is not in conflict with any observations. We have therefore determined current-mass ratios of the light quarks in second-order chiral perturbation theory, with attention to the relative sign of the up-quark mass. We discuss an ambiguity which makes it impossible to determine the quark mass ratios from chiral-Lagrangian considerations alone. Using results from lattice QCD we resolve the ambiguity to obtain $m_u$/$m_d$=0.61±0.26, $m_s$/$m_d$=21±2, implying that ${\theta }_{\mathrm{QCD}=0\mathrm{}}$. .AE

A search for unstable heavy neutral leptons has been made at center-of-mass energies from 50 to 60.8 GeV with the AMY detector at the KEK Storage ring TRISTAN. The neutral leptons are assumed to decay via mixing to electrons and muons. Events with two leptons were searched for. No evidence for their existence was found. Limits in the mass range &≤28.1 GeV/$c^2$ and mixing-parameter range 9×${10}^{\mathrm{-}10}$≤‖$U_{\mathrm{lL}}$${\Vert }^2$≤1 are presented for Dirac- and Majorana-type neutrinos.

We exploit the experimental energy dependence of the neutron-lead scattering cross section to bound the mass of the Higgs boson, $m_H$. We use the recently determined coupling constant of the Higgs particle to nucleons, g=2.1×${10}^{\mathrm{-}3}$, and find $m_H$≳18 MeV.

The branching ratio of φ→$K^0$K¯ ${}_{}{}^0{}_{}{}^{}\gamma$ is calculated to be ${10}^{\mathrm{-}5}$–${10}^{\mathrm{-}6}$. Because of the soft photon involved, this decay could be an important background in future $K^0$K¯ ${}_{}{}^0{}_{}{}^{}$ factories.

The photon spectrum from $K^{\mathrm{-}}$ stopping in liquid hydrogen has been measured with a high-resolution (1.5% FWHM at 300 MeV) NaI(Tl) detector. The branching ratios for $K^{\mathrm{-}}$p→Λγ ($E_{\gamma }$=281.4 MeV) and $K^{\mathrm{-}}$p→${\Sigma }^0$γ ($E_{\gamma }$=219.5 MEV) were obtained. The results are ${\mathit{R}}_{\mathrm{\Lambda }\gamma }$=(0.86±0.${07}_{\mathrm{-}0.08}^{+0.1\mathrm{}}$)×${10}^{\mathrm{-}3}$ and ${\mathit{R}}_{\mathrm{\Sigma }0\gamma }$=(1.44±0.${20}_{\mathrm{-}0.10}^{\pm 0.12}$)×${10}^{\mathrm{-}3}$ where the first error is statistical and the second systematic. These results are not in good agreement with published predictions or with previous Λγ measurements.

We calculate the M1 spectrum and the distorted-wave Born-approximation (e,e’) form factors of the strong ${\mathrm{K}}^{\mathrm{\pi }}$${=1\mathrm{}}^{+}$ states in ${}_{}{}^{164}{}_{}{}^{}\mathrm{Dy}$, using a deformed Woods-Saxon potential and the quasiparticle random-phase approximation with quadrupole, spin, and spin-quadrupole interactions. A residual rotation-vibrational coupling ensures the exclusion of the spurious state. We find strongly orbital M1 states at 3.1 MeV which fit the experimental spectrum very well and exhaust 40% of the collectivity of the $1^{+}$ mode. The form factor of the lowest one of these states is also in a good agreement with the experimental form factor.

Electron cooling of trapped antiprotons allows their storage at energies 10 million times lower than is available in any antiproton storage ring. More than 60 000 antiprotons with energies from 0 to 3000 eV are stored in an ion trap from a single pulse of 5.9-MeV antiprotons from LEAR. Trapped antiprotons maintain their initial energy distribution over a storage lifetime exceeding 50 h unless allowed to collide with a cold buffer gas of trapped electrons, where- upon they cool dramatically to 1 eV in tens of seconds. The cooled antiprotons can be stacked into a harmonic potential well suited for long-term storage and precision measurements.

The photoionization cross section of hydrogen in an electric field is calculated as the sum of resonance contributions, apart from background. Each contribution is proportional to the imaginary part of the square of a complex transition-dipole matrix element divided by an energy denominator and has an asymmetric line shape that is the superposition of dispersive and absorptive Lorentzians. The main features of experiments on the ground and n=2 states, including asymmetry of the lines and blue shift of maxima with respect to calculated resonances near zero energy, are reproduced ab initio. .AE

Photoionization of mass-selected cluster ions ${\mathrm{K}}_{\mathrm{n}}^{+}$ is obtained in the size range 19≤n≤300. Photoproducts are observed by mass spectroscopy at photon energies from 3.5 to 6.2 eV, for several laser flux densities. Mass spectra reveal a competition between photoionization and photoinduced evaporation in the parent ion. The measurements of appearance potentials of doubly and triply charged clusters combined with the first ionization potentials available in the literature allow one to distinguish clearly between the two opposing scaling laws proposed in the literature.

Single mode homogeneously broadened Raman laser emission is shown to be mathematically reducible to a simple description similar to that of the Haken-Lorenz model. However, the physically distinct lasing mechanism involving a two-photon interaction with an equivalent two-level system in a noninverted state allows for considerably relaxed operating conditions where periodic, chaotic, and bistable behavior are identified. Results are in good accord with earlier experiments.

The spectrum of the resonance fluorescence light from a single two-level atom in a small, high-quality, optical cavity is calculated. The coupling between the atom and cavity is made sufficiently strong compared to the dissipation that single quantum frequency splitting (vacuum Rabi splitting) occurs. Under high excitation qualitatively new fluorescent spectra are predicted. The usual three-peaked resonance fluorescence spectrum now has sidebands whose width is given by the Jaynes-Cummings atom-cavity coupling coefficient rather than by the system dissipation.

We explore fundamentals of low-frequency current drive produced by a packet of arbitrarily polarized nonlinear shear Alfvén waves in an infinite, uniform magnetized plasma. Analysis of the magnetohydrodynamic equations with resistivity and viscosity yields coupled nonlinear equations for the Alfvén wave amplitude and an induced magnetic field. Particular solutions relate the plasma current to the helicity of the Alfvén wave and the difference between the viscosity and magnetic diffusivity.

The connection between current drive by plasma waves and helicity conservation is discussed. The mean current drive depends on the difference between the viscous and resistive damping whereas the helicity input depends on the sum of the damping rates. The discrepancy is due to the helicity lost through flucutating currents. In a purely resistive plasma this loss is twice the helicity input and the helicity used in current drive is equal but opposite to the input.

Cyclotron radiation of both fast (Alfvén waves) and slow (Bernstein) waves from a mode-conversion layer is considered to find relations between cyclotron absorption and emission in an inhomogeneous plasma. The relative emission ratios among various modes are calculated and asymmetries of emission are discussed. From relations between emission and absorption, a form of Kirchhoff’s law for a mode-conversion layer is proved from general thermodynamic arguments and from the mode-conversion tunneling equation.

Shapes of laser-produced alkali-hydride crystalline particles (laser snow) are observed for the first time. Particles are suspended by an electric field so as to grow large enough to be observed by an optical microscope. It is found that the particles are single crystals and have particular shapes depending on the gas temperature and the laser-light intensity.

Raman measurements of solid normal deuterium compressed in a diamond-anvil cell indicate that the material undergoes a structural phase transformation at 190±20 GPa and 77 K. Spectroscopically, the transition appears analogous to that observed in hydrogen at 145±5 GPa. The large isotope effect on the transition pressure suggests there is a significant vibrational contribution to the relative stability of the solid phases of hydrogen at very high densities.

The energetics of hydrogen atoms interacting with yttrium have been investigated using the self-consistent cluster model and the local-density approximation. Our results provide a theoretical understanding of a range of novel phenomena observed recently in resistivity, neutron scattering, NMR, and channeling experiments. These include pairing of hydrogen at low temperatures and their structural origin, the anomalous fast diffusion of hydrogen along the pairing axis compared to the bulk rate, and the lack of long-range order between the pairs in metal matrix.

The Mössbauer spectral intensity of ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$ impurities in Pb with concentration of 5%, 2%, 1%, and 1/2% is measured as a function of temperature. A single narrow line is observed which slightly narrows as the temperature increases. Above a temperature $T_c$≪$T_m$, the bulk melting temperature, the Mössbauer integrated intensity drops precipitously from a Debye-Waller behavior. Analysis of the results shows that a small region around each Sn atom is in a state of relatively large entropy, suggesting a local behavior more similar to a liquid than a solid.

First-principles calculations of stress and energy have been performed on 1×1 substitutional and √3 × √3 adatom-covered Si(111) and Ge(111) surfaces, using a variety of column-III, -IV, and -V adsorbates. Trends in surface stresses are understood in terms of three contributing factors: the relative atomic size of the adsorbate and substrate atoms, the chemical nature of the adsorbate species, and the bonding topology of the surface reconstruction.