Rainbow-shift mechanism behind discrete optical-potential ambiguities

Journal Article · Fri Mar 01 00:00:00 EST 1991 · Physical Review, C (Nuclear Physics); (USA)

DOI:https://doi.org/10.1103/PhysRevC.43.1140· OSTI ID:6141251

Brandan, M E ^[1]; McVoy, K W ^[2]

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1. Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Distrito Federal Mexico (Mexico)
2. Department of Physics, University of Wisconsin, Madison, Wisconsin (USA)

Some years ago, Drisko {ital et} {ital al}. suggested that the discrete ambiguity often encountered for elastic scattering optical potentials could be understood as being due to the interior or small-{ital l} {ital S}-matrix elements for two equivalent'' potentials differing in phase by 2{pi}, {ital l}-by-{ital l}. We point out that the {ital absence} of this phase change for peripheral partial waves is equally essential, and suggest that a deeper understanding of the ambiguity may be achieved by viewing it as a consequence of a farside interference between interior and peripheral partial waves. It is this interference which produces the broad Airy maxima'' of a nuclear rainbow, and we show that a Drisko-type phase-shift increment {delta}{sub {ital l}}{r arrow}({delta}{sub {ital l}}+{pi}) for low-{ital l} phases relative to the high-{ital l} ones is exactly what is needed to shift a farside rainbow pattern by one Airy maximum, thus providing an equivalent rainbow-shift'' interpretation of the discrete ambiguity. The physical importance of both interpretations lies in the fact that the existence of discrete ambiguities (as well as of nuclear rainbows) is explicit evidence for low-{ital l} transparency in nucleus-nucleus collisions. The essential role played by low partial waves explains why peripheral reactions have generally not proven helpful in resolving this ambiguity.

• OSTI ID: 6141251
• Journal Information: Physical Review, C (Nuclear Physics); (USA), Vol. 43:3; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
NUCLEAR REACTIONS
OPTICAL MODELS
ANGULAR DISTRIBUTION
COUPLED CHANNEL THEORY
DWBA
ELASTIC SCATTERING
INELASTIC SCATTERING
MATRIX ELEMENTS
PHASE SHIFT
RESONANCE
S MATRIX
SCATTERING AMPLITUDES
SEMICLASSICAL APPROXIMATION
AMPLITUDES
BORN APPROXIMATION
DISTRIBUTION
MATRICES
SCATTERING
653003* - Nuclear Theory- Nuclear Reactions & Scattering