Implications of spin-current couplings forP±Ain inelastic proton scattering

Abstract

Nonlocal spin-dependent couplings in the effective nucleon-nucleon interaction are shown to probe current spin correlations in inelastic nuclear excitations. Together, these couplings and correlations provide an important dynamical source of polarization-analyzing-power differences observed in inelastic proton scattering. This is illustrated explicitly by schematic calculations for 0+ -+1+ and 0+~0 transitions. More realistic distorted-wave impulse approximation calculations have been made for the 0+~1+ transition in~Z r at E"=8. 9 MeV which support the more transparent schematic considerations. Distorted-wave impulse approximation calculations are also compared with experimental (p, p') data for the two lowest 1+ excitations in ' C. For isovector 0+~1+ transitions these nuclear structure spin s current correlations also enter P decay through the "induced tensor" couplings, and this relationship is used to help identify the nonlocality in the nucleon-nucleon effective interaction.

Relativistic effects in proton-proton bremsstrahlung

“…Inclusion of V", introduces a "composite" current (convection spin) term into V, . The composite currents also appears in other reactions such as (p, p') when the spin-dependent part of the NN coupling is momentum dependent [18], as arises from an analogous two-component reduction [19] of the Dirac spinors, for example. We note that in Eq.…”

Comparison of nucleon-nucleon potential models in proton-proton bremsstrahlung

“…The nucleon electric charge is denoted by e, and o; stands for the Pauli spin matrix for nucleon i ( Inclusion of V, introduces a "composite" current (convection spin) term into V, . The composite currents also appear in other reactions such as (p, p') when the spindependent part of the NN coupling is momentum dependent [15] as arises from an analogous two-component reduction [16] of the Dirac spinors, for example. The remaining relativistic correction V" in Eq.…”

Simultaneous measurements of (p→, p→′) and (Wells1, Wissink2, Bacher3 et al. 1995Phys. Rev. C

“…(4) and (5) the induced polarization P and all five of the normal-component analyzing powers measured here (both singles and coincident observables) can be shown PO] to be sensitive to interferences between individual amplitudes in which both the proton and the recoil nucleus polarizations lie in the reaction plane. These same interference terms, which are expected [12]to be particularly sensitive to the nonlocal character (e.g., via exchange) of the NN interaction, can be isolated in the induced polarization and analyzing power difference P -Ay which we have determined using two completely different techniques. Our final values for this quantity, along with the five calculations described earlier, are shown in Fig.…”

“…A measurement of P A~a t 150 MeV [-10] for the 15.11 MeV state in ' C showed this indeed to be the case, as did a later measurement of this observable at 400 MeV for the same state [11].In both cases, inclusion of the tensor-exchange piece of the interaction was crucial in order for the DWIA calculations to agree with the measured values. This prompted detailed theoretical investigations by Love and Comfort [12] who were able to show, in a nonrelativistic framework, that isovector, 0+~1+ transitions were sensitive to the coupling of the nucleon spin to the bound nucleon current, and that understanding how these couplings arise through exchange was important for interpretation of the P -A data for these transitions. It was later shown, in relativistic treatments of proton-nucleus scattering [13,14], that these same nuclear current terms appear more naturally in a relativistic formalism through the linear couplings between the upper and lower components of the bound nucleon wave function.…”