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▪ Abstract Major progress in nuclear research and in observations of the cosmos has made it clear that critical issues in understanding the nucleus and astrophysical processes require abundant new sources of exotic nuclei, away from the realm of the stable ones. Recent advances in accelerator and isotope-production technology make access to these rare isotopes possible. This review examines the impact of the new reach in physics provided by a rare isotope accelerator in nuclear structure, astrophysics, and searches for physics beyond the standard model. We also touch briefly on some of the benefits of these isotopes for other important societal needs.

I discuss the issue of the “transition” between hadronic and quark degrees of freedom. I review the pertinent existing world data concerning this issue, particularly in low energy deuteron photodisintegration, including new unpublished results.

The A(e,e'K+)YX reaction has been investigated in Hall C at Jefferson Laboratory for 6 different targets. Data were taken for Q2)approx 0.35 and 0.5 GeV2) at a beam energy of 3.245GeV for 1)H, 2)H, 3)He, 4)He, C and Al targets. The missing mass spectra are fitted with Monte Carlo simulations taking into account the production of Lambda and Sigma0) hyperon production off the proton, and Sigma-) off the neutron. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for Lambda-hypernuclear bound states is seen for 3,4)He targets.

An experiment was completed at the Stanford Linear Accelerator Center in which measurements of the (e,e{prime}p) coincidence quasielastic cross section in nuclei were extended to the largest possible Q{sup 2} attainable with the Nuclear Physics Injector and the End Station A spectrometers. Coincidence measurements of the quasielastic (e,e{prime}p) cross section were made on nuclei from carbon to gold in the Q{sup 2} range of 1-7 (GeV/c){sup 2}. Several papers describing the results were published or submitted. Analysis of the data is in its final stages. In summary, the cross section for quasielastic {sup 12}C(e,e{prime}p) scattering was measured at momentum transfer Q{sup 2}=1, 3, 5, and 6.8 (GeV/c){sup 2}. The results are consistent with scattering from a single nucleon as the dominant process. The nuclear transparency is obtained and compared with theoretical calculations that incorporate color transparency effects. No significant rise of the transparency with Q{sup 2} is observed. Cross sections were reported for the reaction {sup 2}H(e,e{prime}p)n for momentum transfers in the range 1.2 {

A proposal was approved by CEBAF PAC7 to measure angular distributions of the proton polarization for the d({gamma},p)n reaction in the GeV region. This proposed measurement will test the validity of extensions of conventional nuclear-physics theories to the higher energy regime. The results of the experiment will further constrain the evidence from SLAC experiments NE8 and NE17 that asymptotic scaling was observed above a photon energy of 1.3 GeV. Photoproton polarization measurements at lower energy indicate that the magnitude of the polarization increases with energy. This is consistent with the observation that polarizations are large in high-energy processes, e.g. A{sub nn} in pp {yields} pp scattering or A{sub y} in pp {yields} {pi}{sup 0}X. However, the polarizations in hadron-hadron scattering are believed to arise from Landshoff mechanisms. The higher energy photoproton experiment will permit the first measurements of polarization for a reaction, {gamma}d {yields} pn, where there are no Landshoff terms. The experiment would make use of a polarimeter installed in either the High Resolution Spectrometer in Hall A or the Short Orbit Spectrometer in Hall C at CEBAF.

Experiment NE17 was granted three days of beam time during the last NPAS run at SLAC. During that time, the cross section data for the {gamma}d {yields} pn reaction were extended up to 2.8 GeV at {theta}{sub cm} = 90{degrees} and up to 4.2 GeV at {theta}{sub cm} = 37{degrees}. Data were also taken at {theta}{sub cm} = 37{degrees} 53{degrees}, and 90{degrees} at E{gamma} = 1.6 GeV so that a complete angular distribution would be available at this energy where an Enhancement at a large angle (143{degrees}) was found during experiment NE8. The results indicate the surprising feature that the cross sections at 90{degrees} and 53{degrees} follow the quark counting rule prediction, while those at 37{degrees} do not. Perhaps this indicates that p{sub T}{sup 2} is a controlling variable in the approach to asymptotic scaling. A manuscript was accepted for publication.

Recent studies of pion electroproduction on the deuteron carried out by the ANL group at ALS, Saclay, show that even in the weakly-bound deuteron, multinucleon processes alter the electroproduction amplitudes in the forward direction. The data provide the first experimental indications for a significant change in the pion-nucleon coupling for nucleons bound in nuclei. It is clear that forward-angle electroproduction may be a sensitive probe of the properties of the pion coupling in the nuclear medium. At CEBAF, we will study longitudinal charged-pion electroproduction (in the excitation region below the delta isobar) along the direction of the momentum transfer where the charge scattering process dominates. Direct comparison of the cross section per nucleon in deuterium and the helium isotopes with the experimental value for the free nucleon will provide estimates of the strength of the nuclear pion field. A Rosenbluth separation of the longitudinal and transverse cross sections will be performed for four-momentum transfers of 2.5 and 10 fm{sup -2}. Measurements for a number of light nuclei will provide useful data on the sensitivity of longitudinal electroproduction to nuclear binding effects. If current conceptions of pion-exchange currents in nuclei are correct, longitudinal electroproduction will be suppressed at the lower momentummore » transfer and enhanced at the higher momentum transfer by multinucleon processes. If on the other hand, as suggested by recent data from Drell-Yan studies of antiquark structure functions, there is no such enhancement, a reformulation of pion exchange models of the medium- and short-range properties of nuclear forces will be required. Our proposal to carry out such a series of measurements at CEBAF using the coincident-pair spectrometer system planned for Hall C was approved. Pions will be observed in the short-orbit spectrometer (SOS) which will serve as the second arm.« less

The lowest T = 2 state (Jπ = 0+) in 8Be was observed as a resonance at Ed = 6962.8 ± 3.0 keV (EX = 27495.8 ± 2.4 keV, λc.m. = 5.5 ± 2.0 keV) in the 6Li(d, γ)8Be reaction. The resonant capture yield to the 17.6 MeV Jπ = 1+, T = 1 state gives λγ = 23 ± 4 eV (1.14 ± 0.20 W.u.), in good agreement with the intermediate coupling model.