We examine the effects of relativistic dynamics and medium-modified electromagnetic form factors on the ratio of transverse to longitudinal response in (e,e’p). Calculations performed in the distorted-wave impulse approximation show that the effects of Dirac dynamics and medium-modified form factors are small. We also show that current data seem consistent with our distorted-wave impulse approximation calculations.

The very neutron-deficient isotope ${}_{}{}^{80}{}_{}{}^{}\mathrm{Zr}$ was produced in the reaction ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$${(}^{58}$Ni, 2n${)}^{80}$Zr at 190 MeV with a cross section of σ=10±5 μb and was identified with the Daresbury Recoil Separator. The observation reflects a fiftyfold increase in sensitivity for in-beam spectroscopy of exotic nuclei. Coincidence measurements between the isolated isotope and prompt gamma radiation allowed the identification of decays from low-lying states at E=290 and 828 keV which indicate that ${}_{}{}^{80}{}_{}{}^{}\mathrm{Zr}$ has an extremely large quadrupole deformation of ${\beta }_2$≊0.4.

The theory of analog pion double charge exchange on semimagic even-even nuclei is examined from the point of view of the nuclear shell model. It is shown that the amplitude for the reaction can be expressed as the sum of two independent functions for an entire shell. A more general relation is also discussed which is true for any shell in which the generalized seniority scheme is valid.

Results from a coincidence measurement of the ${}_{}{}^{16}{}_{}{}^{}$O(${\pi }^{+}$,${\pi }^{+}$${\pi }^{\mathrm{-}}$) &=280 MeV are reported, the first of this class. The energy- and angular-integrated cross section was found to be 2950±450 μb and is compared with theoretical predictions. Low-energy positive-pion intensities are found to be much higher than those yielded by a four-body phase-space calculation.

In the local-density and semiclassical approximation, a relativistic Vlasov equation is constructed from the Walecka model. Applying it to heavy-ion collisions at intermediate energies, we obtain results that are similar to those from the more complicated time-dependent Dirac equation. Compared with the results from the nonrelativistic Skyrme interaction, the relativistic effect is evident in the enhanced transverse-momentum distribution during the collision.

Laser-polarized lithium vapor with density ${10}^{14}$ ${\mathrm{cm}}^{\mathrm{-}2}$ in a differentially pumped cell was developed and used as a target in the nuclear fusion reaction ${}_{}{}^6{}_{}{}^{}(\mathit{\alpha }$,γ${)\mathrm{}}^{10}$B. A large change (25%) in reaction cross section relative to an unpolarized target was observed.

We have succeeded in measuring at 0° and small angles the energy spectra for the (d,2p${[\mathrm{}}^1$$S_0$]) reaction (with the two protons in the singlet S state) at 650 MeV and 2 GeV. It is demonstrated that the reaction is a one-step process that can be used to study isospin-spin excitations. The Δ excitation is very clearly observed. A shift down in energy of the Δ peak from the proton to the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ target is observed. The experiments are performed with a tensor polarized beam and the tensor analyzing power for the p($d_{\mathrm{pol}}$,${\mathrm{}}^2$He)n reaction at 2 GeV is given.

Measurements have been made of the ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}=180\mathrm{}}$° cross sections for transfer reactions of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${+}^{116,118,120,122,124}$Sn at energies below the Coulomb barrier using a recoil mass separator. The largest single channel is for one-nucleon pickup, the cross section for which shows a strong dependence on target isotope. This dependence is correlated with the ground-state Q values for one-neutron pickup and is the same as that observed for subbarrier fusion for these systems.

The Steinwedel-Jensen hydrodynamic model is generalized to study isovector collective modes excited in charge-exchange reactions. Results are given for the energy splittings between the different isospin components of the giant dipole and monopole resonances recently observed in (p,n) and (${\pi }^{\pm }$,${\pi }^0$) reactions. The quenching of the Δ$T_z$=+1 excitation strength in N≠Z nuclei with respect to the N=Z case is also discussed.

The S-matrix pole structure of the ${\mathrm{J}}^{\mathrm{\pi }}$${=(3/2\mathrm{}}^{+}$ resonance in ${}_{}{}^5{}_{}{}^{}\mathrm{He}$ is obtained from R-matrix parameters for the system. Two poles are found on different unphysical Riemann sheets. One is a conventional resonance that is primarily responsible for structure in the n-α total cross section. The other is a ‘‘shadow’’ pole that contributes to the large values of the cross section for the reaction ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(d,n${)\mathrm{}}^4$He at low energies. It is the first experimental evidence for the existence of shadow poles in nuclear and particle physics. The two-pole structure of the resonance accounts for different peak positions and widths in the amplitudes for the n-α total cross section and for the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(d,n) reaction cross section.

A kinematically complete experiment on ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(π,dN)N absorption in flight reveals an absorption mechanism in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ with only one spectator nucleon. This adds to the evidence that modes beyond the two-nucleon mechanism contribute to the pion absorption process.

The nuclear magnetic moments of ${}_{}{}^{213}{}_{}{}^{}\mathrm{Ra}$ and ${}_{}{}^{225}{}_{}{}^{}\mathrm{Ra}$ have been measured at ISOLDE (isotope separator at the CERN synchrocyclotron) by observation of the Larmor precession of optically pumped atoms in a fast beam. The results ${\mu }_I$(${}^{213}$Ra)=0.6133(18)${\mu }_N$ and ${\mu }_1$${(\mathrm{}}^{225}$Ra)= -0.7338(15)${\mu }_N$ provide an accurate test of ab initio and semiempirical calculations from optical hyperfine structures in Ra i and Ra ii. .AE

Transverse-momentum measurements of collective flow are analyzed in terms of scale-invariant quantities. Deviation from the fluid-dynamical scaling behavior, at energies below $E_{\mathrm{lab}=200\mathrm{}}$ MeV/nucleon, indicates a drastic change in the reaction mechanism. This might be due to a liquid-gas phase transition and nuclear mean-field effects.

We introduce an expression for the deformed nuclear density in gauge space in terms of the pairing deformation parameter ${\mathrm{\beta }}_{\mathrm{P}}$. The Fourier components of this quantity as functions of the ordinary space variables can be used to define macroscopic form factors for multiparticle transfer processes in superfluid nuclei. Experimental ΔN-particle transfer cross sections for ΔN=±2, ±4, etc., analyzed within this framework yield the relative magnitudes of the Fourier amplitudes. This procedure therefore allows for the reconstruction of density contours in the abstract space.

Evidence is presented for five closely spaced states in ${}_{}{}^{118}{}_{}{}^{}\mathrm{Cd}$ near $E_{\mathrm{ex}\mathrm{\simeq }2}$ MeV, which are interpreted as a near-harmonic three-phonon quintuplet. Candidates for even higher-lying multiphonon states are also found. The experimental spectrum is compared with an anharmonic vibrator [or U(5) spectrum] and an interacting-boson-approximation calculation incorporating a two-particle, four-hole intruder configuration.

Neutrinoless double-β decay would require two new phenomena, of which one is lepton-number nonconservation. Among several candidates for the other are nonzero neutrino mass and the emission of a Goldstone boson, such as the majoron. For the former possibility our Ge-detector array now sets a limit for the $0^{+}$→$0^{+}$ transition in ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ of $T_{1/2}$>5×${10}^{23}$ yr from the fluctuation in the background or almost a factor of 2 longer by maximum likelihood at the 68% confidence level (C.L.). For the latter process we have a 90%-C.L. limit of 1.4×${10}^{21}$ yr, a result in disagreement with a recent possible observation of majoron emission.

Conditions for the applicability of, and possible corrections to, the Dirac equation in a broad variety of nuclear processes are derived in the framework of the additive constituent-quark model. In particular, we find that in small–momentum-transfer scattering of composite nucleons from spin- and isospin-zero nuclei, Z diagrams on the level of individual quarks reproduce those resulting from pointlike nucleons, in the approximation that constituent quarks carry equal fractions of the nucleon momentum. Deviations from the Dirac equation, on the other hand, may occur in interactions of nucleons with nuclei of nonzero spin or isospin.

Data on inclusive electron scattering from A=4, 12, 27, 56, 197 nuclei at large momentum transfer are presented and analyzed in terms of y scaling. We find that the data do scale for y<0 (x>1), and we study the convergence of the scaling function with the momentum transfer $Q^2$ and A.

The distribution of magnetic dipole transition strength in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ has been measured at excitations between 8.1 and 10.5 MeV with highly polarized tagged photons. A total M1 strength of Jg${\mathrm{\Gamma }}_0^2$(M1)/ Γ${=37.7\mathrm{}}_{\mathrm{-}4.0}^{+5.1\mathrm{}}$ eV was found to be broadly distributed throughout the region. This strength can account for the giant M1 resonance predicted in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$. A substantial amount of E1 transition strength was also identified. This E1 strength has important implications for the interpretation of forward-angle (p,p’) scattering and its use in identifying M1 transitions in heavier nuclei.

The assumption that the distribution of reduced partial-width amplitudes is multivariate Gaussian is tested by separate measurement of width and amplitude correlations. The data are transformed to a representation in which the amplitude correlation is zero, and the width correlation is compared directly with the predicted value of zero. The average width correlation for 21 data set is r${\mathrm{¯}}_{\mathrm{w}}$=-0.01, providing the most direct and assumption-free verification that the global amplitude distribution is multivariate Gaussian. The significance of this result for current studies of quantum chaos is discussed.