We consider pseudo-Dirac-type neutrinos with Majorana masses which are smaller than their Dirac ones. It is shown that there are two possible kinds of resonant neutrino oscillations for each generation, whose interplay provides an economical way to solve the puzzles of solar and atmospheric neutrinos simultaneously.

It is observed that the scale-unifying model based on supersymmetry and compositeness provides a natural reason for the family mass hierarchy m${\mathrm{¯}}_{\mathit{e}}$≪m${\mathrm{¯}}_{\mathrm{\mu }}$≪m${\mathrm{¯}}_{\mathrm{\tau }}$ and links spontaneous CP violation to the nonvanishing mass of the electron family. Some of its predictions include (i) ${\mathit{K}}^{0\mathrm{-}}$K¯ ${}_{}{}^0{}_{}{}^{}$ and ${\mathit{K}}_{\mathit{L}}$→μ¯e are normal, but (ii) Z→tc¯, cū, and μe¯ have observably large strengths, allowing for single top production at the CERN ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ collider LEP II, and (iii) ${\mathit{d}}_{\mathit{n}}$≊(0.5–10)×${10}^{\mathrm{-}26}$ cm.

Using the CLEO II detector at the Cornell Electron Storage Ring, we have determined the inclusive ${\mathit{B}}^{\mathrm{*}}$ cross section above the Υ(4S) resonance in the energy range from 10.61 to 10.70 GeV. We also report a new measurement of the energy of the ${\mathit{B}}^{\mathrm{*}}$→Bγ transition photon of 46.2±0.3±0.8 MeV.

Using the CsI calorimeter of the CLEO II detector, the spin triplet ${\mathrm{\chi }}_{\mathit{b}}$(2P) states are observed in Υ(3S) radiative decays with much higher statistics than seen in previous experiments. The observed mass splittings are not described well by theoretical models, while the relative branching ratios agree with predictions that include relativistic corrections to the radiative transition rates.

Recent lattice calculations of static hadronic-screening lengths and the quark-number susceptibility are interpreted in terms of a simple constituent quark model. The conclusion is that just above ${\mathit{T}}_{\mathit{c}}$ the nature of the hadronic modes is rather well described in terms of elementary π and σ, as well as light-quark, modes. Hence chiral symmetry in the absence of symmetry-breaking terms is realized through massless quarks rather than through parity doubling.

We discuss the possibility of measuring the magnetic dipole moment ${\mathrm{\mu }}_{\mathit{W}}$ and the electric quadrupole moment ${\mathit{Q}}_{\mathit{W}}$ of the weak gauge bosons at heavy-ion colliders. This measurement amounts to a test of the gauge structure of the standard model. We show that the total cross section for W-pair production via γγ fusion is very sensitive to ${\mathrm{\mu }}_{\mathit{W}}$ and ${\mathit{Q}}_{\mathit{W}}$, thus allowing a precise determination of their values.

Recent improvements to both the instrumentation and data-analysis techniques associated with the Manitoba II high-resolution mass spectrometer have led to greater precision and accuracy. The mass difference between ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ and ${}_{}{}^{76}{}_{}{}^{}\mathrm{Se}$ has been redetermined to be 2038.56(32) keV. When this new Q value is used to reexamine recent spectra reported by groups searching for the characteristic sharp peak expected for neutrinoless double-beta decay, no evidence for the occurrence of such a decay is found. New upper limits can be derived for the electron-neutrino mass.

Negative chlorine ions are stored in a Penning trap and are exposed to short (35 ps) and intense (up to 3×${10}^{12}$ W/${\mathrm{cm}}^2$) optical pulses with a wavelength of 1064 nm. The detached electrons are detected in energy-resolved measurements. Absorption is observed of up to two photons in excess of what is required on the basis of the electron affinity.

We present a new quantum nondemolition measurement scheme in which a measure of the photon statistics of a cavity field can be achieved by monitoring the deflection of atoms interacting with the field. Repeated measurements result in the collapse of the photon distribution in the field to a number state. Quantum jumps in the photon number are observed when the cavity field is coupled to an external reservoir.

Four quarklike eight-dimensional spinors are used to generate the states of the atomic f shell. The automorphisms of SO(8) are put to work through the three SO(7) subgroups of Labarthe. As an example, selection rules are derived for two three-electron operators used in rare-earth and actinide spectroscopy.

We show that light-induced mechanical forces that act on atoms may be significantly enhanced and acquire novel physical character when the electromagnetic reservoir which mediates the atomic relaxation is colored (i.e., frequency dependent).

The quantum statistical behavior of a small collection of N two-state atoms strongly coupled to the field of a high-finessse optical cavity is investigated. Input-output characteristics are recorded over the range 3≲N≲65, with bistability observed for N≳15 intracavity atoms and for a saturation photon number ${\mathit{n}}_0$≃0.8. For weak excitation the transmitted field exhibits photon antibunching as a nonclassical manifestation of state reduction and quantum interference with the magnitude of the nonclassical effects largely independent of N.

Multiphoton detachment of ${\mathrm{Au}}^{\mathrm{-}}$ is studied at an irradiation wavelength of 1064 nm and for optical pulses of ∼40 ps duration and maximum intensity ∼3×${10}^{12}$ W/${\mathrm{cm}}^2$. The negative gold ion can be detached by absorption of a minimum of two 1.165-eV photons which leads to ejection of ∼20-meV electrons. Utilizing a time-of-flight electron spectrometer, the absorption of up to two excess photons is observed with a probability, normalized to the lowest-order peak, of ∼5% and ∼0.6%, respectively, for first- and second-order excess-photon detachment.

Resonances in atomic ions can be used to search for new, weak, spin-dependent interactions. Upper limits on anomalous dipole-monopole and dipole-dipole couplings for the neutron and electron are determined by examining hyperfine resonances in stored ${}_{}{}^9{}_{}{}^{}\mathrm{Be}_{}^{+}{}_{}{}^{}$ ions. These experiments also place strict limits on anomalous weights of spinning gyroscopes.

We present a Lagrangian calculation of the area of isothermal (or isoconcentration) surfaces in a medium of fluid turbulence. We argue that such surfaces appear fractal above some inner scale which depends on the Reynolds number. The fractal dimension is estimated theoretically. The theory is compared to experiments in which a dye is used as a passive scalar in various turbulent flows. We find excellent agreement in many details.

We have measured gain profiles by light-beating techniques for an argon-ion laser operated above threshold. The observed behavior is interpreted by developing a theory which incorporates four-wave mixing of signal and image frequencies. The gain shows the typical characteristics of a second-order phase transition. We also discuss the implications for fundamental laser noise, and predict strong correlations between the noise contributions from either side of the laser frequency.

Modulation of the beam current has been observed during ion-focused-regime (IFR) transport of a high-power relativistic electron beam propagating through a low-density background plasma. In this experiment, a 1.7-MeV, 1-kA, rise-time-sharpened electron beam is transported in a KrF-excimer-laser–produced IFR channel in trimethylamine gas. The IFR channel is immersed in a low-density plasma-filled transport tube. We present experimental measurements and computer simulations demonstrating modulation of this high-current relativistic electron beam near the low-density background plasma frequency.

Molecular-dynamics simulations of noncohesive granular assemblies under shear are described. At low shear rate γ̇, the assembly is unstable to uniform motion and exhibits stick-slip dynamics involving periodic dilatancy transitions and gravitational compactification. Steady-state motion occurs at larger γ̇ where 6–12 layers of grains flow over a compact, static assembly. A phase boundary, characterized by a discontinuity in γ̇ and an enhanced normal stress, separates the static and flowing regions. In the steady-state regime, dilatancy leads to a shear stress that is independent of γ̇.

The expansion of laser-ablation plasmas in a magnetic field is studied with a new Faraday-rotation magnetic imaging probe and Fourier-analyzed optical plasma images over a wide range of ion magnetization. Plasma instabilities are observed during the plasma expansion which evolve from short to long wavelengths and significantly affect the magnetic structure.

The scanning tunneling microscope (STM) was used to quantitatively investigate nonequilibrium surfaces of graphite roughened by sputter etching with 5-keV Ar ions. The resulting surface morphology depended strongly on the ion flux and fluence, as well as the sample temperature. The height-correlation functions of the roughened surfaces were calculated directly from the STM topographs and compared to linear-response theory and scaling analyses for the propagation of growing fronts. The surfaces developed correlated structures characterized by a length that diverged with increasing ion fluence.