In view of the lack of any firm theoretical evidence for the principle of charge quantization, we propose testing its validity experimentally by looking for particles with small electric charges (Q∼${10}^{\mathrm{-}3}$e). Toward this aim we investigate various constraints on their masses and charges and discuss the problem of the experimental search for them. As a byproduct we find that such particles may solve the orthopositronium-lifetime puzzle.

Electroweak quantum effects are studied in the ${\mathit{M}}_{\mathit{W}}$-${\mathit{M}}_{\mathit{Z}}$ relation by using recent data of ALEPH, DELPHI, L3, OPAL, and Mark II Collaborations on ${\mathit{M}}_{\mathit{Z}}$, and those of CDF and UA2 Collaborations on ${\mathit{M}}_{\mathit{W}}$. It is shown that these data demand the existence of a ${\mathit{G}}_{\mathit{F}}$${\mathit{m}}_{\mathit{t}}^2$-type correction in addition to the well-known logarithmic terms, which gives new phenomenological support to the electroweak theory independent of the neutral-current data.

We have searched for the inclusive reaction ${\mathit{D}}_{\mathit{s}}^{\pm }$→${\mathit{e}}^{\pm }$X using a tagged sample of 68 ${\mathit{D}}_{\mathit{s}}^{\pm }$ produced in the reaction ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$→${\mathit{D}}_{\mathit{s}}^{\pm }$${\mathit{D}}_{\mathit{s}}^{\mathrm{*}\mp }$ at a center-of-mass energy of 4.14 GeV. The tagged sample consists of the decays ${\mathit{D}}_{\mathit{s}}^{+}$→φ${\mathrm{\pi }}^{+}$, ${\mathit{D}}_{\mathit{s}}^{+}$→K¯ ${}_{}{}^{\mathrm{*}0}{}_{}{}^{}$${\mathit{K}}^{+}$, and ${\mathit{D}}_{\mathit{s}}^{+}$→K¯ ${}_{}{}^0{}_{}{}^{}$${\mathit{K}}^{+}$. We determine B(${\mathit{D}}_{\mathit{s}}^{+}$→${\mathit{e}}^{+}$X)=0.${05}_{\mathrm{-}0.05}^{+0.05\mathrm{}}$±0.02, which corresponds to a limit of B(${\mathit{D}}_{\mathit{s}}^{+}$→${\mathit{e}}^{+}$X)<0.20, at the 90% confidence level.

It is demonstrated that existing np→dX data show a strong signal for the two-body reaction np→dη near its threshold. The cross sectio n is much larger than that for the analogous ${\mathrm{\pi }}^0$ threshold production, but is in accord with a model where production is dominated by the ${\mathit{S}}_{11}$ ${\mathit{N}}^{\mathrm{*}}$(1535) resonance. The Abashian-Both-Crowe enhancement ${\mathit{X}}_{\mathrm{ABC}}$ is a prominent feature of the data. It is shown that the np→${\mathit{dX}}_{\mathrm{ABC}}$ process at 1.9 GeV/c, which contains most of the 2π production, is almost isotropic, in constrast to theoretical models.

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ nuclei. Our result is ${\mathit{A}}_{\mathrm{expt}}$=0.60±0.14±0.02 ppm, where the first error is statistical and the second is systematic. With a beam polarization of 0.37, we compute the isoscalar vector hadronic coupling constant γ̃ to be 0.136±0.032±0.009. The standard model predicts γ̃=0.155 at the tree level, in agreement with our data.

We report a measurement of the asymmetry in spin-dependent quasielastic scattering of longitudinally polarized electrons from a polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ gas target. This measurement represents the first demonstration of a new method for studying electromagnetic nuclear structure: the scattering of polarized electrons from a polarized nuclear target. The measured asymmetry is in good agreement with a Faddeev calculation and supports the picture of spin-dependent quasielastic scattering from polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ as predominantly scattering from a polarized neutron.

The interaction of two linearly cross-polarized beams having frequencies ${\mathrm{\omega }}_1$ and ${\mathrm{\omega }}_2$ with sodium atoms leads to the generation of new waves having frequencies (2p+1)${\mathrm{\omega }}_1$-2p${\mathrm{\omega }}_2$. The intensities of these waves are well explained by a simple model based on self-induced optical activity. The relation with the atomic cooling in a polarization gradient and with the exact resonances in multiwave mixing is pointed out.

We report the first measurements of the polarization of x rays emitted from bound-bound transitions in a highly ionized He-like ion. Polarization was measured for the decay to the ground state, 1${\mathit{s}}^2$ ${}_{}{}^1{}_{}{}^{}$${\mathit{S}}_0$, of the He-like ${\mathrm{Sc}}^{19+}$ levels 1s2p ${}_{}{}^1{}_{}{}^{}$${\mathit{P}}_1$, 1s2p ${}_{}{}^3{}_{}{}^{}$${\mathit{P}}_2$, 1s2p ${}_{}{}^3{}_{}{}^{}$${\mathit{P}}_1$, and 1s2s ${}_{}{}^3{}_{}{}^{}$${\mathit{S}}_1$. The measurements were made with the Electron Beam Ion Trap at two electron-beam energies: 4.36 and 5.62 keV. Polarization of two of the lines is strongly influenced by the hyperfine interaction with the Sc nucleus, demonstrating that polarization measurements can be used to investigate hyperfine interactions in highly ionized atoms.

Fundamentally, the electron and muon transfer mechanisms are the same. We report on muon transfer from the ground state of muonic hydrogen to neon, measured in the gas mixtures ${\mathrm{H}}_2$+Ne and ${\mathrm{H}}_2$+Ne+Ar. Unexpectedly, the muonic x-ray time spectra measured in the binary mixture show two components. From the extracted transfer rates, the higher one agrees with an older experiment, whereas the lower one, which is reproduced in the triple gas mixture, was not observed before.

The macrotemporal structure of a storage-ring free-electron laser is studied in relation to deterministic chaos laws. Comparison between experimental and theoretical results shows, for the first time, that the laser is determined by these laws. This can have important consequences for the future operation of free-electron lasers.

It is found through computer simulations of plasma-filled backward-wave oscillators that within a certain range of magnetic field the growth rate of beam-plasma cyclotron interaction is significantly larger than the conventional backward-wave oscillation. This slow plasma cyclotron wave is emitted from plasmas only if it also satisfies the dispersion relation of a rippled-wall waveguide which couples the slow wave to fast wave. This observation may be employed to interpret previous experiments which displayed a strong dependence of output power on the magnetic field.

Magnetic reconnection phenomena are investigated taking into account all three vector components of the magnetic field in a laboratory experiment. Two toroidal magnetized plasmas carrying identical toroidal currents and poloidal field configurations are made to collide, thereby inducing magnetic reconnection. The direction of the toroidal field plays an important role in the merging process. It is found that plasmas of antiparallel helicity merge much faster than those of parallel helicity. It is also found that the reconnection rate is proportional to the initial relative velocity of the two plasma tori, suggesting that magnetic reconnection, in the present experiment, is a forced phenomenon.

Two superelastic percolation models are proposed to explain the observed behavior of the viscosity η of gels near the gel point. The elastic moduli G of one model diverge at the percolation threshold ${\mathit{p}}_{\mathit{c}}$ with a critical exponent τ given by τ=ν-${\mathrm{\beta }}_{\mathit{p}}$/2, where ν and ${\mathrm{\beta }}_{\mathit{p}}$ are the critical exponents of percolation correlation length and the strength of the infinite cluster, respectively. We propose that this system can model the behavior of η in the Zimm limit. In the second model, which we propose to be appropriate for the Rouse limit, G diverge at ${\mathit{p}}_{\mathit{c}}$ with an exponent τ’=2τ. Large-scale simulations confirm these scaling laws. The experimentally observed deviations from these scaling laws are also discussed.

The barrier to self-diffusion on Al(001) by concerted displacement in a 〈100〉 or 〈010〉 direction is predicted to be smaller than 1/3 that for ordinary Al-adatom hopping over bridges between fourfold hollows. The transition state for the concerted motion corresponds to an Al ad-dimer symmetrically located above a surface site vacated by one of the dimer atoms. Covalent bonding in this configuration is favorable because each of the (trivalent) Al atoms above the surface bonds to the other, and to two surface atoms.

The discovery of a reentrant layer-by-layer growth during molecular-beam epitaxy of Pt on Pt(111) is reported. Explanations of the reentrant behavior based on previous field-ion-microscopy observations are proposed.

The evolution of ${\mathrm{Cu}}_3$Au(110) surface order from ${10}^2$ to ${10}^5$ s after disordering anneals has been monitored by low-energy electron diffraction. On the basis of refined observations of the profiles of diffracted beams, it is concluded that the early stage of surface ordering consists of the nucleation of compositionally ordered microclusters prior to bulk ordering.

Coadsorption of potassium is observed to significantly enhance photodissociation of Mo(CO${)}_6$ adsorbed on Cu(111) and Si(111)7×7 by opening a completely different photodissociation channel. In addition to the direct photoelectronic excitation of Mo(CO${)}_6$ on K-free surfaces, the dominant photodissociation process on K-coadsorbed surfaces involves attachment of photogenerated hot electrons to the adsorbate, which is energetically possible due to substantial decreases in the work function.

We consider the most probable value of conductance of a disordered quantum conductor in the framework of the random matrix theory developed earlier. Analytic calculations are possible in the metallic as well as strongly localized regimes. We make a simple assumption on the eigenvalue density, as suggested by numerical work, and explore the consequences of a one-parameter distribution. A key result of the one-parameter scaling theory, that there is true metallic behavior only in dimensions greater than two, is recovered naturally.

The investigation of shell structure in the ground states of atoms is limited to values of the angular momentum quantum number l≤3. In atomic nuclei, shells with l≤6 can be observed. We present evidence for shell structure in the electronic states of metal clusters for l≤12.

The conduction bands of direct-gap III-V semiconductors are shown to be effectively universal near the Γ point even when strongly nonparabolic, for energies in effective rydbergs and wave numbers in inverse effective lattice constants. This implies universality of the diamagnetic Shubnikov–de Haas effect in the nonparabolic regime in some two-dimensional electron gases, as observed experimentally. A two-band k⋅p approximation together with Harrison’s model-solid theory explains this near universality and relates its systematic deviations to the covalency of the material in question.