We suggest a unified gauge theory based on a spontaneously broken SU(4) ⊗ U(1) symmetry. It is the presence of additional gauge bosons in our model which is responsible for muon-number-nonconserving processes. We have considered specifically $\mu \to e\gamma$, $\mu \to 3e$, and $\mu +\mathfrak{N}\to e+\mathfrak{N}$, and find that the last process is the most amenable to experimental detection.

We consider models in which heavy leptons are produced in neutrino reactions and then decay sequentially into trimuons. In all these models leptons and quarks are in the 3 or $3^{*}$ representation of the gauge group SU(3) ⊗ U(1).

We have studied the threshold production and decay angular distribution of neutral charmed mesons produced in $e^{+}{e}^{-}$ annihilation. We find consistency with the expected spin values of 0 and 1 for the ground and excited states $D$ and $D^{*}$, respectively. We rule out the alternative spin assignment of 1 for the $D$ and 0 for the $D^{*}$.

A classical analysis of recent fusion cross sections is presented. The results are consistent with a schematic model previously published by the author, and allow one to extract an empirical nucleus-nucleus potential.

Multiphoton processes are detected in the scattering of electrons on argon atoms in the presence of a strong C${\mathrm{O}}_2$-laser field. The observations are in accordance with a recently developed semiclassical model.

Hydrodynamic and molecular-dynamics calculations show that the charge fluctuations in a strongly coupled ${\mathrm{H}}^{+}$-${\mathrm{He}}^{++}$ mixture are dominated by a propagating plasmon mode which is damped by interdiffusion even in the long-wavelength limit. A sum-rule argument indicating that the plasmon dispersion changes from positive to negative as the coupling increases is consistent with both kinetic theory and the computer results. Plasma oscillations also contribute weakly to the mass fluctuations, but there is no hydrodynamic soundwave mode.

Numerical hydrodynamic simulations which include absorption and transport modifications due to ion-acoustic turbulence have been performed. These simulations can reproduce the important features of the fast-ion velocity distributions as measured with biased charge collectors and a magnetic spectrograph in spherically illuminated microballoon experiments. Experiments with hemispherical targets show that a substantial amount of fast-ion energy is directed inward and may contribute to driving the implosion.

It is shown both experimentally and theoretically that a Bernstein wave can decay parametrically into another Bernstein wave and a whistler-mode wave. The process only occurs in a highly collisionless plasma and it is suggested that this is the dominant mechanism for producing whistler-mode noise in the auroral ionosphere.

An enclosing "box" calorimeter has been used to measure the polarization and angular dependence of 1.06-μm laser-light absorption under experimental conditions approximating those assumed by Estabrook, Valeo, and Kruer in their simulations; i.e., ∼${10}^{16}$ W/${\mathrm{cm}}^2$ plane waves incident on a planar plasma. A clear resonance absorption maximum was observed for $p$-but not for $s$-polarized incident radiation as predicted.

A simple model involving resonant absorption in a self-consistent sharp density gradient is found to be in quantitative agreement with the suprathermal-electron spectrum from recent laser-plasma-interaction experiments and to explain qualitatively the scaling of that suprathermal-electron spectrum with laser power and wavelength.

Pd and Pt clusters on carbon substrates have been studied by x-ray photoemission spectroscopy (XPS). Variations in valence- and core-level spectra with cluster size have been observed. Single-atom centers appear to exist in the $d^9{s}^1$ configuration. The $d$-electron count increases with cluster size, and in the case of Pt a correlation between $d$-orbital occupation and catalytic activity in electroless nickel deposition is observed.

We have observed sharp structure in the $I-V$ characteristics of Al-$\mathrm{Al}{\mathrm{O}}_x$-PbBi tunnel junctions induced by tunnel injection of excess quasiparticles into the Al film. Interpretation of this structure provides information on the form of the steady-state quasiparticle energy distribution, showing that it is highly nonthermal. The data also demonstrate the presence of a branch imbalance in the injected Al film.

The dependence of impact ionization rates upon electric-field orientation is demonstrated in GaAs and is related to specific features of the electronic band structure. This effect has profound implications for the interpretation and implementation of avalanche phenomena in semiconductors.

The reaction field generated by a point dipole in a polarizable medium is considerably underestimated and the screening of the dipolar field is considerably overestimated by the classical continuum theory. The importance of the induced-dipole-induced-dipole contribution, particularly in reducing the screening in a normal liquid, is demonstrated by molecular-dynamics computer calculations.

A strong temperature dependence has been observed for the first time in angle-resolved photoemission (ARP) spectra of the valence band of a crystalline solid. This spectral behavior confirms predictions of a model suggested by Shevchik. A controversial point in the interpretation of ARP spectra at x-ray energies is resolved by this model. Moreover, it dictates the choice of photon energy and sample temperature for future ARP studies of valence-band electronic structure.

The present cosmic mass density of possible stable neutral heavy leptons is calculated in a standard cosmological model. In order for this density not to exceed the upper limit of 2×${10}^{-29\mathrm{}}$ g/${\mathrm{cm}}^3$, the lepton mass would have to be greater than a lower bound of the order of 2 GeV.

An upper bound on the lifetime of a massive, neutral, weakly interacting lepton, ${\nu }_H$, is derived from standard big-bang cosmology. Saturation of the bound and reasonable assumptions about the weak interaction of the ${\nu }_H$ then yield a prediction of approximately 10 MeV for its mass.

Radiochemical measurements of cross sections for 173 nuclides produced in the reaction of 538-MeV ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ ions with thick ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ targets were performed and the mass-yield curve determined. Seven components were resolved, corresponding to three reaction mechanisms: (1) quasielastic transfer (810 ± 160 mb); (2) quasifission (350 ± 55 mb); (3) fusion-fission (190 ± 30 mb). Comparison with data from other systems indicates that the fusion-fission cross section for heavy targets depends strongly on projectile mass and target- to projectile-mass ratio.

This paper presents a model based on the assumption of the existence of "correlated clusters" which stay as they are during a fast collision. The model can explain remarkably well the inclusive spectra of energetic protons at 180° in the proton-nucleus experiments by Frankel et al.

Fragments with $1<~Z<~12$, some with energies as low as 3 MeV/nucleon and some with energies as high as 120 MeV/nucleon, have been analyzed in high-energy nucleus-nucleus reactions with C, Ne, and Ar projectiles. For a given projectile the invariant cross sections of all fragments appear to define a "universal" curve that is exponential in momentum, provided momentum is evaluated in a frame in which the distribution is isotropic. The low speed of the frame (∼0.01c to ∼0.1c) suggests emission from the recoiling target.