We have determined the coherent $K_S$ regeneration amplitudes on various nuclei, from 20 to 140 GeV/c, using a particularly systematics-free technique. Our results are well represented by $\left|\frac{(f-\overline{f})}{k}\right|=2.23\mathrm{}{A}^{0.758}{p}^{-0.614\mathrm{}}$ mb. This $p$ dependence corresponds to an effective "nuclear" intercept $``{\alpha }_{\omega }\mathrm{}\left(0\right)\text{'}\text{'}=0.386\mathrm{}\pm 0.009$, whereas the elementary value is ${\alpha }_{\omega }\mathrm{}\left(0\right)=0.44\mathrm{}\pm 0.01$. Comparisons are made with data below 25 GeV/c, and with optical-model predictions. The latter work only if "${\alpha }_{\omega }\mathrm{}\left(0\right)\mathrm{}$" is postulated to hold for the elementary amplitudes.

A spin-dependent eikonal amplitude for the scattering of two fermions by vector-meson exchanges is extended to include spin dependence due to pseudoscalar exchanges as well. The result is applied to elastic $p-p$ scattering by using a primitive, energy-dependent Chou-Yang model augmented by pion exchange. The spin dependence introduces dramatic energy dependence resembling that observed.

A general analysis of the gauge group SU(2) ⊗ U(1) ⊗ U′(1) is carried out and models are constructed that admit positive result for parity nonconservation in electron-deuteron scattering while giving small parity nonconservation in bismuth.

Excitation energies, spins, and parities have been determined for ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ in (HI, $\mathrm{xn}$) reactions up to $I^{\pi }={27}^{+}$. Three isomers with $T_{\frac{1}{2}}=49.5\mathrm{}$ ns ($E_x=5035\mathrm{}$ keV, $I^{\pi }={16}^{+}$), 9.9 ns ($E_x=6076\mathrm{}$ keV, $I^{\pi }={20}^{-}$), and 1.6 ns ($E_x=7828\mathrm{}$ keV, $I^{\pi }={26}^{-}$) have been found. The $g$ factor of the second isomeric state was measured to be $g=0.55\mathrm{}\pm 0.06$.. The present experimental data compares well with microscopic calculations which imply an oblate shape for ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ at high angular momenta ($I^{\pi }>~{16}^{+}$).

The ($e$,$p$) and ($e$,$\alpha$) cross sections for targets of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{62}{}_{}{}^{}\mathrm{Ni}$ have been measured in the electron energy range 16-50 MeV. They have been analyzed using the distorted-wave Born-approximation $E1\mathrm{}$ and $E2\mathrm{}$ virtual-photon spectra. Protons are emitted primarily following $E1\mathrm{}$ absorption but $\alpha$ emission results from a combination of $E1\mathrm{}$ and $E2\mathrm{}$ absorption. The $E2\mathrm{}$ isoscalar giant resonance decays predominantly by $\alpha$ emission for these nuclei.

We report the large-$\mathcal{r}$ and small-$\mathcal{r}$ expansions of the one-particle reduced density $\stackrel{\mathrm{`}}{\mathrm{m}}$atrix $\rho \left(\mathcal{r}\right)$ of a system of impenetrable bosons in one dimension at zero temperature. These expansions were derived from an exact calculation of $\rho \left(\mathcal{r}\right)$ to be reported elsewhere. We find that the large-$\mathcal{r}$ expansion of $\rho \left(\mathcal{r}\right)$ contains oscillatory terms which we relate to the analytic structure of the momentum density function $n\left(k\right)\mathrm{}$.

A unified optical-model analysis of neutron and proton elastic scattering from Mo isotopes reveals breakdowns of the Lane model of $\overrightarrow{\mathrm{t}}·\overrightarrow{\mathrm{T}}$ interactions, most clearly evident as shell effects. The puzzle is that a coupled-reaction-channel reanalysis does not remove these.

Energy and isotope distributions were measured for peripheral reactions induced by ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ at 213 MeV/nucleon. The data are consistent with the predictions of abrasion-ablation models. The influence of correlations in the nuclear ground state is discussed.

The ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ giant dipole resonance is calculated with a continuum shell model which treats the center of mass correctly and includes possible noncentral components of the nucleon-nucleon interaction. The ($\gamma$,$p$) and ($\gamma$,$n$) cross sections and asymmetry coefficients agree well with the experiment. The $b_2$ asymmetry coefficient is shown to depend on the spin-orbit odd component of the effective nuclear force. The $1^{-}$ level positions and channel mixing are in best agreement with "solution II" of the $R$-matrix fit of Werntz and Meyerhof.

Yields of projectile fragments have been measured at 0° for the reaction of 205-MeV/nucleon ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ ions on an 860-mg-${\mathrm{cm}}^{-2\mathrm{}}$ carbon target. Mass resolution was achieved using a combination of magnetic analysis and energy-loss measurements. The isotopes ${}_{}{}^{28}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{35}{}_{}{}^{}\mathrm{Al}$ have been observed for the first time.

Observation of $\beta$-delayed protons from the decay of the mass-separated $T_z=-2\mathrm{}$ nuclide ${}_{}{}^{20}{}_{}{}^{}\mathrm{Mg}$ ($t_{\frac{1}{2}}\sim 95$ ms) establishes the mass excess of the lowest $T=2\mathrm{}\left(0^{+}\right)$ state in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ (13.42 ± 0.05 MeV), thereby completing the mass-20 isospin quintet. All members of this multiplet are bound to isospin-allowed particle-decay modes, providing the first test of the isobaric multiplet mass equation for such a quintet. Excellent agreement is observed using only the quadratic form of this equation.

We propose that the quenching of Gamow-Teller matrix elements in light nuclei can be effectively described by a mechanism that governs the $p$-wave pion-nucleus scattering. This may be providing a solution to the long-standing problem. The resulting Landau-Migdal parameter $g^{\prime }$ turns out to be quite consistent with the values extracted from the spectra of pionlike excitations and places a stringent constraint on pion condensation in nuclear matter.

Consideration of core polarization, meson exchange, and relativistic corrections gives a satisfactory, quantitative understanding of mirror Gamow-Teller $\beta$-transitions in $A=3, 15, 17, 39, \mathrm{and} 41$ nuclei.

Systematic variations in nuclear-matter distributions have been determined by analyzing the measured elastic scattering of 140-MeV alpha particles from ${}_{}{}^{46,48,50}{}_{}{}^{}\mathrm{Ti}$. The "unique" optical potentials obtained ($\frac{J_{\mathrm{R}}}{4A}\simeq 300$ MeV ${\mathrm{fm}}^3$, $\frac{J_{\mathrm{I}}}{4A}\simeq 100$ MeV ${\mathrm{fm}}^3$) indicate that isotopic differences occur primarily in the strength of the imaginary potential. The rms matter radii increase with $A$, in contrast to those of the charge distributions. The matter-radius results are in agreement with Hartree-Fock calculations.

An expression given by Fock for the density matrix in momentum space of an electron in the $n\mathrm{th}$ hydrogenic shell is used to derive a prescription for calculating capture cross sections into arbitrary principal shells of energetic bare projectiles. Application to an eikonal treatment yields a simple formula showing that capture cross sections scale to the Oppenheimer-Brinkman-Kramers values with a $Z$-independent factor between 0.1 and 0.4, in agreement with experimental data.

On the basis of a sample of 41 events of the type $e^{+}{e}^{-}\to e^{\pm }{X}^{\mp }\left(X\ne e\right)$ and no observed photons, we have observed a clear signal of the decay ${\tau }^{-}\to {\pi }^{-}{\nu }_{\tau }$. We measure the branching ratio for this decay to be $b_{\pi }=0.080\mathrm{}\pm 0.032\pm 0.013$ and for the decay ${\tau }^{-}\to {\mu }^{-}{\overline{\nu }}_{\mu }{\nu }_{\tau }$, $b_{\mu }=0.21\mathrm{}\pm 0.05\pm 0.03$,where the first and second errors are, respectively, statistical and systematic. Both measurements agree with theoretical values derived under the assumption that the $\tau$ decays via the standard weak current.

The order-disorder transition in Cs-intercalated graphite has been studied using x-ray scattering. In ${\mathrm{C}}_8$Cs the Cs layer transforms into a liquidlike phase in which the average Cs-Cs separation is incommensurate with the carbon net. Fundamentally different behavior is observed in a Cs-deficient stage-1 sample where commensurate "lattice-gas" melting occurs. Evidence is presented which shows that in low-stage material, staging is closely related to the melting transition in support of the model of Daumas and Hérold.

A model of a monolayer of atoms adsorbed on a crystalline surface is discussed. When the initial incommensurability, $\delta$, between a reciprocal lattice vector of the monolayer and one of the substrate is small, the monolayer has a one-dimensional superstructure with period depending on $\delta$. For $\delta >{\delta }_c\mathrm{}\left(T\right)\mathrm{}$ the state is incommensurate; ${\delta }_c\mathrm{}\left(T\right)\mathrm{}$ decreases and vanishes at a $T_c$ given by the elastic moduli of the monolayer. The spectrum of small oscillations has two acoustic branches, one vanishing at the phase transition.

In contrast to the case of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, we find no evidence for spontaneous nucleation of a uniform surface solid layer from the liquid phase of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ near Grafoil substrates. However, surface solid could be detected after forcing the rapid growth of bulk solid from external points of nucleation. The experiment covers the temperature range between 30 and 320 mK at pressures just below the bulk melting curve.

A many-electron approach to double exchange which explicitly considers the indistinguishability of mobile and valence electrons has been developed. The theory is applied to small-polaron motion in magnetic systems. The temperature dependence of the small-polaron mobility in antiferromagnets is shown to differ significantly from that in paramagnets and ferromagnets.