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Mackintosh, R. S. and Keeley, N.
(2024).
DOI: https://doi.org/10.1103/PhysRevC.109.034605
Abstract
Background: Well established coupled channel (CC) and coupled reaction channel (CRC) processes make contributions to the elastic scattering optical model potential (OMP) that are not represented in local density folding models.
Purpose: We aim to establish and characterize the contribution to the 3He and 3H OMPs generated by coupling to proton or neutron pickup and stripping channels, in particular for 33 MeV 3He and 3H OMPs on 40Ca; also stripping for 40 MeV 3He.
Methods: CRC calculations provide the elastic channel S matrix, Slj, generated by the included processes. Inversion of Slj then produces a local potential, including a spin-orbit term, that yields, in a single channel calculation, the elastic scattering observables from the CRC calculation. Subtracting the bare potential then gives a local and l-independent representation of the dynamical polarization potential, DPP.
Results: Pickup generates greater OMP absorption for 3He than for 3H. Neutron stripping for 3H generates much greater absorption than proton stripping for 3He. Neutron pickup for 3He has a substantial repulsive effect. All stripping and pickup processes reduce the rms radius of the OMP. None of the coupling effects can be represented by a uniform renormalization of the OMP. A comparison of 33 and 40 MeV 3He stripping yields evidence of energy dependence of DPPs with available data.
Conclusions: The DPPs challenge the notion that local density folding models can provide a satisfactory description of elastic scattering from nuclei. No standard form global OMP could fit precisely 3He or 3H elastic scattering from 40Ca. For both pickup and stripping coupling, the increase in reaction cross section is much less than the cross section to the coupled channel states, which is the opposite of what was found in many other cases.
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