The current-current quark model provides a two-parameter description of the $S$- and $P$-wave nonleptonic decay amplitudes of hyperons.

It is shown that the negative transverse-angle correlation between leading particles in multiparticle production, required by momentum and energy conservation, is substantially reduced if the secondaries are correlated in longitudinal momentum with the leading particles. The multiperipheral model, which has the pions produced with ordered longitudinal momenta, and a pionization model, which has each pion produced randomly in longitudinal phase space, are compared with experimental results for $\mathrm{pp}\to \mathrm{pp}{\pi }^{+}{\pi }^{+}{\pi }^{-}{\pi }^{-}$ at 23 $\frac{\mathrm{GeV}}{c}$. The data strongly favor random pion production.

We make a definitive test which distinguishes $s-$ from $t$-channel helicity conservation in $\pi N$ scattering. A quantitative measure of the $I_t=0\mathrm{}$ helicity-flip amplitude is proposed and evaluated using only polarization data. The violation of $s$-channel helicity conservation is found to die away with a ${\left(P_{\mathrm{lab}}\right)}^{-2}$ energy dependence in the range 2 to 11 GeV.

Using only the surface-anisotropy constants and the saturation magnetization as adjustable parameters, we have found good agreement between an observed and a calculated spin-wave resonance spectrum. A uniform magnetization, effects of exchange, conductivity, and Landau-Lifshitz damping are included in the theory.

Magnetic specific heat and susceptibility measurements have shown that ${\mathrm{Na}}_3$[${\mathrm{C}\mathrm{e}\left({\mathrm{C}}_7{\mathrm{H}}_3\mathrm{N}{\mathrm{O}}_4\right)}_3$] · 15H2O has extremely weak effective spin-spin interactions, suggesting that this material may be a useful alternative to cerium magnesium sitrate for very low temperature thermometry.

Pb $K$ x rays and ∼ 1.08-MeV $K$-conversion electrons have been found among radiations emitted in the decay of 4.2-min ${}_{}{}^{206}{}_{}{}^{}\mathrm{Tl}$. These radiations imply the existence of weak $\beta$ transitions (0.08%) to the 1.17-MeV $0^{+}$ state in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$, which decays primarily by an $E0\mathrm{}$ transition to the ground state.

The neutron-photon angular-correlation and energy spectrum of neutrons from radiative pion capture by carbon are presented and provide new evidence for excitation of a $J^{\pi }=1^{-}$ axial-vector collective mode. Asymmetry in the angular correlation increases with neutron energy and is accounted for by direct neutron emission.

The simplest direct mechanism (pole diagram) for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{12}{}_{}{}^{}\mathrm{C},\alpha ){}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ has about as much gross structure as the data. Thus, the hypothesis of a compound or "doorway" mechanism is unnecessary.

The polarization of neutrons elastically scattered from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at 50° has been measured as a continuous function of energy between 2 and 5 MeV using a neutron double-scattering technique. This measurement provides an absolute standard for polarization studies in this energy range. The intense pulsed yield of neutrons obtained from the first scatterer is shown to be a practicable source of polarized neutrons suitable for high-resolution experiments in the MeV region.

The (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$) reaction was observed for targets of ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$ at 41 MeV. The reaction displays features expected from the pickup of an $\alpha$-like fragment. The values of the cross sections agree with a prediction based on known proton spectroscopic factors. Contrary to current shell-model predictions, the trend of (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$) cross sections does not require that the $\alpha$ spectroscopic factors change by more than 1 order of magnitude from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ to ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$.

We have performed a deuteron-proton double-scattering experiment with a 3.6-$\frac{\mathrm{GeV}}{c}$ deuteron beam to study the spin alignment of the elastically scattered deuterons. We observed scattered beams of polarized deuterons and have measured the spin alignment and vector polarization in the four-momentum-transfer interval of ${\Delta }^2=0.13\mathrm{} \mathrm{to} 0.54 {\left(\frac{\mathrm{GeV}}{c}\right)}^2$. Multiple-scattering model fits are presented to our alignment and polarization data as well as to existing differential-cross-section data.

We discuss the possibility that the interesting large, high-energy cross section for $\gamma +\gamma \to e^{+}+e^{-}+e^{+}+e^{-}$ can be indirectly tested via the reaction $\gamma +Z\to Z+e^{+}+e^{-}+e^{+}+e^{-}$. As a by-product, the background caused by the former process in the Primakoff-Stodolsky method for measuring the total photon-photon cross section into hadrons is shown to be substantially reduced beyond naive expectations.

Within the framework of Faddeev theory we calculate the binding energy of the lowest bound state of three identical particles. Excluding three-body potentials, the particles are assumed to interact mutually via a two-body Morse potential. Finally, our model calculations are applied to a system formed of three helium atoms. Using a Morse potential which is fitted to the He-He interaction potential calculated by Bertoncini and Wahl, our calculation predicts a stable triatomic helium molecule with a binding energy of 0.4°K, even though a diatomic helium molecule does not exist for the same well depth.

The elastic differential and total helium-helium scattering cross sections are computed at very low energies. Retardation effects, which are accurately taken into account by using the arc tangent approximation to the Casimir-Polder potential, are shown to contribute several percent to the cross sections.

This Letter reports numerical simulations of three-dimensional homogeneous isotropic turbulence at wind-tunnel Reynolds numbers. The results of the simulations are compared with the predictions of the direct-interaction turbulence theory.

The dispersion in the phase velocity of first sound in He II at 1.38°K was measured between 20 and 60 GHz (1-3°K). The results show direct experimental verification of positive dispersion in the phonon branch. The dispersion in the sound velocity was measured to be $C\left(\nu \right)=C_0[1+(6.3\mathrm{}\pm 0.7)\times {10}^{-13\mathrm{}}\nu +(0\mathrm{}\pm 8)\times {10}^{-25\mathrm{}}{\nu }^2]$.

A class of exact statistical equilibria for the Navier-Stokes equation not including viscosity in two dimensions is noted and the corresponding fluctuation spectrum calculated. These solutions may account for the phenomena recently observed in numerical simulations of two-dimensional turbulence by Deem and Zabusky, including the existence of two distinct regimes of turbulence and the relaxation of one of these towards equipartition of vorticity.

A resonance absorption occuring in the classical optics of thin films for incident light at the plasma frequency is proposed to explain the reflectance and absorptance observed concurrently with neutron production in the heating of deuterium targets with Nd:glass laser pulses.

Computer simulations of the fluidlike modified two-stream instability, driven by relative electron-ion drifts across a magnetic field, show strong anomalous plasma heating. The electron and ion heating rates are comparable and result in ion thermal speeds which approach the relative drift speed within a few ion plasma periods.

Based on empirical evidence, it is suggested that the energy band structure in PbPo may be inverted from that in PbS, PbSe, and PbTe. This inversion would result in PbPo having an ${L_6}^{+}$ conduction-band edge and an ${L_6}^{-}$ valence-band edge, implying a negative value of the energy gap $E_G=\left[E\right({L_6}^{-})-E({L_6}^{+}\left)\right]$, and a negative value of $\frac{d{E}_G}{\mathrm{dT}}$. We propose an experiment to test this hypothesis.