Search

The isoscalar spin‐transfer signature Syd has been used in inelastic scattering of 400 MeV polarized deuterons to search for ΔS=1 ΔT=0 strength in 40Ca and 12C. In 40Ca, spin excitations were found in the 9 MeV region and over a broad range in the continuum with a cluster strength around 15 MeV. In 12C, a previously unknown ΔS=1 ΔT=0 level was observed at 20.5 MeV; ΔS=1 ΔT=0 resonances were also found at 20 MeV and 30 MeV. Microscopic DWIA calculations agree nicely with 12C data.

A focal plane polarimeter intended for the CEBAF Hall A high resolution hadron spectrometer is under construction at Rutgers University and the College of William & Mary. Experiments with focal plane polarimeters are only now beginning at electron accelerators; they play a prominent role in the list of approved experiments for Hall A. Construction of the polarimeter is in progress, it is expected to be brought to CEBAF in spring 1995. Several coincidence (e,e′p) and singles (γ,p) measurements by the Hall A Collaboration are expected to start in 1996. In this paper we describe the polarimeter and the physics program planned for it.

The polarization of the outgoing protons has been measured for small angle inelastic scattering from 90Zr and 51V with a 319 MeV incident polarized proton beam. The measured spin‐flip cross section is a direct measure of the spin excitations in the nucleus. The results for 90Zr show a large spin‐flip cross section is a direct measure of spin excitations in the nucleus. The results for 90Zr show a large spin‐flip cross section which is approximately evenly distributed between 8 and 25 MeV excitation; the Ml region is not prominent. Preliminary data for 51V also reveal large continuum spin excitations, as well as a clear peak in the Ml region. The data are discussed in relation to the search for missing spin excitation strength in the delta region and to electron scattering results.

A program has begun to measure the angular and energy dependence of differential cross sections (dsigma/domega) and vector analyzing power A/sub ..gamma../ of the pp ..cap alpha.. d..pi.. reaction between 725 and 1000 MeV, in steps of about 25 MeV, using the polarized proton beam of Saturne 2. Data have been fitted using Legendre functions. 6 references, 2 figures.

Measurements of the spin‐flip probability Snn for inclusive inelastic proton scattering around 300 MeV determine the relative ΔS=1/(ΔS=0+ΔS=1) response of the nucleus provided Snn is a ‘‘robust’’ observable. Recent data then give a general picture of the nuclear spin response up to about 40 MeV of excitation for momentum transfers up to about 200 MeV/c. Slab model calculations give qualitative agreement with much of the data; they explain the small values at high excitation. They do not explain the values approaching 90% for intermediate momentum transfers. RPA calculations which localize the S=0 strength at lower excitation energies, coupled with a shift in S=1 strength to higher excitations.