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Title: Rainbow-shift mechanism behind discrete optical-potential ambiguities

Abstract

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 reactionsmore » have generally not proven helpful in resolving this ambiguity.« less

Authors:
 [1];  [2]
  1. Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Distrito Federal Mexico (Mexico)
  2. Department of Physics, University of Wisconsin, Madison, Wisconsin (USA)
Publication Date:
OSTI Identifier:
6141251
Resource Type:
Journal Article
Journal Name:
Physical Review, C (Nuclear Physics); (USA)
Additional Journal Information:
Journal Volume: 43:3; Journal ID: ISSN 0556-2813
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Brandan, M E, and McVoy, K W. Rainbow-shift mechanism behind discrete optical-potential ambiguities. United States: N. p., 1991. Web. doi:10.1103/PhysRevC.43.1140.
Brandan, M E, & McVoy, K W. Rainbow-shift mechanism behind discrete optical-potential ambiguities. United States. https://doi.org/10.1103/PhysRevC.43.1140
Brandan, M E, and McVoy, K W. 1991. "Rainbow-shift mechanism behind discrete optical-potential ambiguities". United States. https://doi.org/10.1103/PhysRevC.43.1140.
@article{osti_6141251,
title = {Rainbow-shift mechanism behind discrete optical-potential ambiguities},
author = {Brandan, M E and McVoy, K W},
abstractNote = {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.},
doi = {10.1103/PhysRevC.43.1140},
url = {https://www.osti.gov/biblio/6141251}, journal = {Physical Review, C (Nuclear Physics); (USA)},
issn = {0556-2813},
number = ,
volume = 43:3,
place = {United States},
year = {Fri Mar 01 00:00:00 EST 1991},
month = {Fri Mar 01 00:00:00 EST 1991}
}