Search

Polarization transfer in the 4He ( e → ,e′ p → ) 3 H reaction at a Q2 of 0.4 (GeV/c)2 was measured at the Mainz Microtron MAMI. The ratio of the transverse to the longitudinal polarization components of the ejected protons was compared with the same ratio for elastic ep scattering. The results are consistent with a recent fully relativistic calculation which includes a predicted medium modification of the proton form factor based on a quark–meson coupling model.

Three different signatures for isoscalar spin transitions in nuclei have been tested in the 12 C( d , d ') 12 C reaction at 400 MeV. These signatures have values of close to zero for the natural parity states, and values ranging from 0.22 to 0.50 for the ΔS =1, ΔT =0, 12.7 MeV state.

Cross sections and analyzing powers have been measured at 800 MeV for inclusive (p, p′) reactions on 1H and 12C in the 300 MeV excitation region. The data for 1H and 12C are qualitatively similar, but differ in detail. A Born approximation model reproduces the cross sections for p + p scattering, but fails to fit the Ay data. Further, while a plane wave impulse approximation calculation reproduces the general features of the 12C(p, p′) cross sections, significant details are not accounted for.

Angular distributions of recoil protons in coincidence with the scattered pions from the reaction ( π + , π − p) on targets of 12 C and 48 Ca are reported. The measurements were made at an incident pion energy of 250 MeV, for a scattered pion angle of 80° and energy of 139 MeV. The angular distribution of recoil protons is broader than expected from a model in which the reaction is assumed to proceed by two sequential pion charge-exchange scatterings from nucleous in a Fermi gas.

Cross sections, analyzing powers, and spin-flip cross sections have been measured at small angles for the 51V( → p, → p′ ) 51V∗ reaction at 319 MeV. In disagreement with electron scattering results but in confirmation of proton scattering data, a clear M1 resonance is observed. Its strength is comparable to that seen in 48Ca and 54Fe. Significant spin excitation strength is observed also above the resonance.

Cross sections for the reaction 13 C(p, d) 12 C ∗ in coincidence with back-to-back, out-of-plane, two-proton decays at high excitation energies (140–420 MeV) are presented for E p = 800 MeV at deuteron laboratory angles of 2.5°, 5.0°, and 9.0°. At all angles a resonant-like enhancement in the cross section is observed at 241 MeV of excitation energy with a width of 55 MeV. Some features of these data indicate that this structure may be related to the formation of low-spin (ΔN −1 ) states in 12 C.

Differential cross sections and analyzing powers have been measured for the 18O ( p , p′) 18O reaction at 800 MeV. A coupled-channels analysis of the 01+, 21+, and 42+ data yields good agreement with a rotational model description with a large β4 deformation. The effects of channel coupling are large. The angular distributions of Ay are reproduced well only with a full Thomas spin-orbit deformation approximately equal to the central deformation.

In addition to the octupole transitions to the apparent weak-coupling doublet [3 s 1 2 −1 , 206 Pb 3 − ] at 2.62–2.71 MeV, three other strong octupole transitions to nearby states are observed in the inelastic scattering of 20 MeV protons from 205 Tl. Two of these extra states, at 3.21 and 3.26 MeV, may arise from the [2 d 3 2 −1 , 206 Pb 3 − ] configuration. It is not likely that the other transition (2.48 MeV) can be described by the simple weak-coupling model.