With the E731 apparatus at Fermilab, we have simultaneously collected 6859 ${\mathit{K}}_{\mathit{L}}$ and ${\mathit{K}}_{\mathit{S}}$ decays into ${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$γ. Using our sample of over 370 000 ${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$ decays for normalization we have determined that the ratio Γ(${\mathit{K}}^0$→${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$γ)/Γ(${\mathit{K}}^0$→${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$) is (23.0±0.7)×${10}^{\mathrm{-}3}$ for ${\mathit{K}}_{\mathit{L}}$ and (7.10±0.22)×${10}^{\mathrm{-}3}$ for ${\mathit{K}}_{\mathit{S}}$, for photon energies greater than 20 MeV in the kaon center of mass. After removing the inner-bremsstrahlung contribution, we find that the photon energy spectrum of the direct emission decay of the ${\mathit{K}}_{\mathit{L}}$ is consistent with the presence of a vector meson propagator in the form factor.

Interference between ${\mathrm{K}}_{\mathrm{S}}$ and ${\mathrm{K}}_{\mathrm{L}}$ decays into the final state ${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$γ has been observed in experiment 731 at Fermilab. By fitting the distribution of decays downstream of a regenerator, a new CP-violation parameter${\mathrm{\eta }}_{+\mathrm{-}\gamma }$, analogous to ${\mathrm{\eta }}_{+\mathrm{-}}$, has been measured, with its magnitude equal to(2.15±0.26±0.20)×${10}^{\mathrm{-}3}$, and ${\mathrm{\phi }}_{+\mathrm{-}\gamma }$, the associated phase angle, equal to(72±23±17)°. Assuming that any difference between this fit value for ${\mathrm{\eta }}_{+\mathrm{-}\gamma }$ and the previously measured value for${\mathrm{\eta }}_{+\mathrm{-}}$ can be attributed to direct CP violation in this decay, a limit of|${\mathrm{\epsilon }}_{+\mathrm{-}\gamma }^{\prime }$|/ε<0.3 at the 90% confidence level has been made. © 1993 The American Physical Society

We use the data on the decays $D\to \pi \pi$ and $D\to \mathrm{KK}$ as a test vehicle for evaluating the effects of penguin diagrams in exclusive heavy meson decays. Evaluating $\Gamma (D\to {\pi }^{+}{\pi }^{-})$ and $\Gamma (D\to K^{+}{K}^{-})$, we find good agreement between our theoretical $\mathrm{SU}\mathrm{}\left(2L\right)\mathrm{}\times \mathrm{U}\mathrm{}\left(1\right)\mathrm{}\times \mathrm{SU}{\mathrm{}\left(3\right)\mathrm{}}^c$-based predictions and observation. Contributions from penguin diagrams are small and SU(3) flavor breaking effects account for the large value of $\frac{\Gamma (D\to K^{+}{K}^{-})}{\Gamma (D\to {\pi }^{+}{\pi }^{-})}$. Implications for $B$ decays are discussed briefly.

Measurement of the helicity asymmetric cross section for semi-inclusive production of Λ hyperons in ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ annihilation near the ${\mathit{Z}}^0$ resonance allows a complete determination of the spin-dependent fragmentation functions for the different quark flavors into the Λ. The parity-violating, self-analyzing, decay of the final state Λ makes the experimental analysis of the helicity asymmetry possible. This experiment should be practical with present day technology at the LEP collider at CERN or at the SLAC Linear Collider.

The spin-orbit splitting of the ${\mathit{p}}_{1/2}$ and ${\mathit{p}}_{3/2}$ hole states in ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ is studied with realistic nuclear forces and the variational cluster Monte Carlo method. The results show that the two-nucleon L⋅S forces give approximately half of the observed splitting, while the other half comes from pion exchange interactions between three or more nucleons. The observed splitting is fairly well reproduced by these calculations based on nonrelativistic nuclear many-body theory.

Proton-proton correlations at small relative momenta were measured for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{197}$Au reactions at E/A=200 MeV. Comparing the correlation functions to predictions based on single-particle phase space distributions from microscopic Boltzmann-Uehling-Uhlenbeck and quantum-molecular-dynamics (QMD) simulations, no satisfactory agreement could be established. Calculations utilizing two-particle emission probabilities predicted by the QMD model differ significantly from the single-particle calculations and are much closer to the experimental observations at E/A=200 MeV, potentially signaling the importance of the two-particle density for the proton-proton correlation function.

We derive the entire singly excited electronc level spectrum of a dipolar molecule (CaF) from atomic properties alone (the quantum defects of ${\mathrm{Cd}}^{+}$). In the approach presented here the motion of the lone electron is treated as a double scattering process involving the closed-shell ${\mathrm{Ca}}^{++}$ and ${\mathrm{F}}^{\mathrm{-}}$ centers with ${\mathrm{F}}^{\mathrm{-}}$ treated as a point charge. The energies of all known electronic states of CaF are well reproduced by the theory. Refinements of the model such as inclusion of the finite volume of ${\mathrm{F}}^{\mathrm{-}}$ or of polarization effects are deferred as are extensions of the model to account for spin-orbit and other fine structure effects.

The nonlinear resonant response of a bound electron to a time-varying spatially inhomogeneous electric field was studied experimentally. By use of the artificial atom ‘‘geonium’’ (an electron bound in a Penning trap), we observed up to ninth-order multipole (pentacosiododecapole) coherent excitation of the electron’s magnetron motion, and up to third-order (octupole) excitation of the cyclotron motion. Also, by applying two fields simultaneously, we have observed coherent stimulated Raman excitation of the electron’s motion.

The behavior of ‘‘overlapping’’ depolarizing resonances was studied using a stored 106.4-MeV polarized proton beam. We used an rf solenoid magnet to create an ‘‘rf induced’’ depolarizing resonance which was then forced to overlap with the Gγ=2 imperfection depolarizing resonance. We found significant interactions between the two resonances by varying their frequencies and strengths; the frequency of the rf resonance strongly affected the response of the imperfection resonance to correction magnetic fields. The Siberian snake overcame all observable depolarization due to the overlapping resonances and maintained full polarization for all observed frequencies and strengths.

Using oblique injection of electron-cyclotron (EC) waves, launched from the low field side of the WT-3 tokamak, into a target plasma sustained by lower hybrid current drive (LHCD), the plasma current is ramped up at a rate corresponding to 100 kA/s. The current ramp-up is ascribed to selective EC heating of tail electrons in the LHCD plasma via fundamental EC resonance at an up-shifted frequency due to the Doppler effect.

Bispectral analysis of Langmuir probe data indicates that coherent nonlinear coupling, in addition to the noncoherent turbulent interactions, exists in the edge plasma of the tokamak TEXT. Not all the modes involved reside within the spectral region of the usual broadband turbulence. At a major resonant surface the small-scale turbulent activity interacts coherently with a localized long-wavelength mode; a signature of regular or coherent structure. By the observed coupling to the transport related turbulence, the long-wavelength mode can influence plasma confinement indirectly. These observations signify the influence of low-order resonant surfaces on the edge turbulence in tokamaks.

Numerical studies of a model of stimulated Raman scattering (SRS) coupled to Langmuir turbulence show that once the collisional threshold is exceeded for parametric decay of the SRS daughter Langmuir wave the noncollisional dissipation resulting from Langmuir collapse can strongly saturate the Langmuir wave and the resulting SRS reflectivity. The model provides information on the total rate of hot electron generation. Scaling laws for the reflectivity as a function of laser and plasma parameters are found.

This paper reports on the first experiments designed to study ion-beam-induced gas ionization and subsequent conductivity growth using intense proton beams transported through various gases in the 1-Torr pressure regime. Net-current fractions of 2 to 8% are measured outside the beam channel. Ionization is confined predominantly to the beam channel with ionization fractions of a few percent. Analysis suggests that net currents are larger inside the beam channel and that fast electrons and their secondaries carry a significant fraction of the return current in a halo outside the beam.

The slow demixing of block copolymer thin films in relief domains is interpreted as a two-dimensional phase transition kinetics following a quench into a biphasic region of a phase diagram. The associated scalar parameter Ψ is a linear function of the local thickness of film. Two samples with critical Ψ’s have been experimentally studied by atomic force microscopy. At long times, the two stable phases draw spinodal decompositionlike patterns. At shorter times, the existence of an additional metastable phase is demonstrated and explained.

We propose a new model for transport in disordered solids and rocks which contain N distinct families of transport paths (N≥2), and study the behavior of its effective transport properties. The model is relevant to transport in metals, polycrystals, porous catalysts, coalbed methane reservoirs, and geological systems with fractures and pores.

We have studied analytically and numerically the shape of the boundary that separates a superfluid from a gas or another liquid in the presence of a vortex normal to the boundary. Our analysis reveals an instability at which a crater appears in the center of the dimple around the vortex in the superfluid, developing abruptly into a cylindrical macrocore filled by the other liquid. At the interface between two superfluids, there is repulsion between the ends of vortices on different sides of the boundary.

Metastable, monolayer-high structures as narrow as one dimer row and as long as the substrate’s terrace width decorate antiphase boundaries on Si(100) following 225 eV Xe bombardment. On the basis of tunneling microscope STM observations and first-principles calculations, we propose that the bonding toplogy of a buckled dimer row on an antiphase boundary is responsible for the metastability of this ‘‘zipper’’ structure, and in turn for the preferential nucleation of dimer rows on antiphase boundaries during growth.

We show that in a semiconductor quantum wire the energy relaxation of the excited one-dimensional electron gas due to acoustic phonon emission is strongly enhanced at low temperatures by a subtle many-body effect arising from the broadening caused by the electron–acoustic-phonon interaction. This broadening opens up a ‘‘virtual’’ channel for energy transfer from the electrons to the low energy tail of the phonon spectral function. This peculiarly one-dimensional many-body effect causes a very large enhancement of the power loss over the bare value and restores the Bloch-Grüneisen power law temperature dependence of the energy loss rate at low temperatures.

We study the dynamics of switching charge-density waves (CDWs) in the presence of combined dc and ac electric fields. Analysis of the time series provides Lyapunov exponents, and an estimate for the number of active degrees of freedom. The dynamics are both low dimensional and chaotic. The principal nonlinearity which gives rise to the chaos in switching CDWs is shown to be the hysteresis in the depinning transition, rather than the interaction between two frequencies.

The infinite-U Anderson model is applied to nonequilibrium transport through a quantum dot containing two spin levels weakly coupled to two leads. At low temperatures, the Kondo peak in the equilibrium density of states is split upon the application of a voltage bias. The split peaks, one at the chemical potential of each lead, are suppressed by nonequilibrium dissipation. In a magnetic field, the Kondo peaks shift away from the chemical potentials by the Zeeman energy, leading to an observable peak in the differential conductance when the nonequilibrium bias equals the Zeeman energy.