The phenomenology of proton elastic scattering and evidence for angular-momentum-dependent optical-model potentials

Kobos, A.M.; Mackintosh, R. S.

doi:10.1088/0305-4616/5/1/012

Cited by 54 publications

(69 citation statements)

References 25 publications

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“…The present work does not solve the problem of how to fit the backward angle AD and AP for 30.3 MeV scattering of protons from 40 Ca. To date, these data have been fit only with nonstandard phenomenology: either L-dependent potentials [26,27] or somewhat wavy potentials found by spline fitting [28]. Whether these data can be fit with a smooth potential plus CRC coupling to pickup channels is a challenge for the future.…”

Section: B What Does It All Mean?mentioning

confidence: 99%

Coupling effects in proton scattering from40Ca

Mackintosh

Keeley

2012

Phys. Rev. C

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Recent studies showed that neutron pickup makes a substantial contribution to the proton optical model potential (OMP) for light, mostly halo, target nuclei. Here, we extend those studies to a more "normal" target nucleus: 40 Ca. We present coupled reaction channel (CRC) calculations with the coupling of 30.3 MeV incident protons to deuterons and up to 12 states of 39 Ca. The proton elastic scattering S matrix from the CRC calculation is subject to S lj → V (r) + l · s V SO (r) inversion and the bare potential of the CRC calculation is subtracted, directly yielding a local and L-independent representation of the dynamic polarization potential (DPP). This is appropriate for comparison with phenomenological OMPs and local OMPs derived in local density folding models. The real-central part of the DPP is repulsive and cannot be represented as a uniform normalization of the bare potential, changing the rms radius. A series of model calculations reveal the dependence of the DPP on a range of parameters illuminating (i) departures of nucleon potentials of specific nuclei from global properties, (ii) the generation of repulsion, and (iii) the requirements for all-order CRC and deuteron breakup. Light is thrown on the nonlocality of the underlying DPP.

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Section: B What Does It All Mean?mentioning

confidence: 99%

Coupling effects in proton scattering from40Ca

Mackintosh

Keeley

2012

Phys. Rev. C

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“…The data in question have never been fitted with smooth potentials of standard parameterized forms. Potentials that fitted these data required unconventional features: l-dependence [2][3][4][5] or undulatory character [6,7]. The need for these unconventional models for nucleon elastic scattering has not been widely accepted because of the deceptive ease with which the generally available elastic scattering data for many (but not all; see Ref.…”

Section: Introductionmentioning

confidence: 99%

Phonon coupling effects in proton scattering fromCa40

Mackintosh

Keeley

2014

Phys. Rev. C

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Background: Formal optical model theory shows that coupling to vibrational nuclear states generates a nonlocal and l-dependent dynamical polarization potential (DPP). Little is established concerning the DPP, yet its properties are crucial for explaining the departures of optical model potentials (OMPs) from global behavior and for the rigorous extraction of spectroscopic information from direct reactions. Purpose: To appraise the application of channel coupling followed by S-matrix inversion for the systematic exploration of the contribution of the coupling of collective states to the nucleon OMP and to identify properties of nuclear potentials indicative of l-dependence. Methods: S-matrix to potential, S lj → V (r) + l · s V SO (r), inversion provides local potentials that precisely reproduce the elastic channel S-matrix from coupled channel (CC) calculations. Subtracting the elastic channel uncoupled (bare) potential yields a local and l-independent representation of the DPP. The dependence of this local DPP upon the nature of the coupled states and upon other parameters can be studied. Results: All components of the DPP arising from coupling to vibrational states are substantially undulatory with a point-by-point magnitude therefore disproportionate to their contribution to volume integrals. Information relating to dynamical nonlocality is found. The proton charge leads to a substantial difference between DPPs for protons and neutrons. Conclusions: Undulatory features in potentials found in precision fits to elastic scattering data are significant, are a consequence of coupling to inelastic channels and must be allowed for in phenomenology; they are indirect evidence of l-dependence. Within the model, coupling to excited states magnifies the effect of the proton charge on the difference between proton-nucleus and neutron-nucleus interactions. Coupled channel plus inversion is a procedure of wide applicability, complementary to evaluation of the Feshbach formalism.

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“…The cross sections were calculated in the optical model for direct capture [6], utilizing optical potentials derived by the folding procedure [7]. In the folding approach the nuclear target density is folded with an energy-and density-dependent effective nucleon-nucleon interaction in order to obtain the potentials for the bound and scattering states.…”

Section: Methodsmentioning

confidence: 99%

Uncertainties in direct neutron capture calculations due to nuclear structure models

Rauscher

Kratz

Dobaczewski³

et al. 1997

Nuclear Physics A

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The prediction of cross sections for nuclei far off stability is crucial in the field of nuclear astrophysics. For spherical nuclei close to the dripline the statistical model (Hauser-Feshbach) approach is not applicable and direct contributions may dominate the cross sections. For neutron-rich, even-even Sn targets, we compare the resulting neutron capture cross sections when consistently taking the input for the direct capture calculations from three different microscopic models. The results underline the sensitivity of cross sections calculated in the direct model to nuclear structure models which can lead to high uncertainties when lacking experimental information.

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The phenomenology of proton elastic scattering and evidence for angular-momentum-dependent optical-model potentials

Cited by 54 publications

References 25 publications

Coupling effects in proton scattering from40Ca

Coupling effects in proton scattering from40Ca

Phonon coupling effects in proton scattering fromCa40

Uncertainties in direct neutron capture calculations due to nuclear structure models

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