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Lorentz-Lorenz Quenching for the Gamow-Teller Sum Rules

  • J. Delorme
  • M. Ericson
  • A. Figureau
  • N. Giraud

Abstract

One of the most striking aspects of the recent detailed exploration of the Gamow-Teller resonances is the systematic observation that the summed axial vector strength is appreciably lower than that expected from the Gamow-Teller sum rule. The latter is obtained under the assumption of additivity of the free nucleon coupling \(g{}_A\overrightarrow \sigma.\overrightarrow \tau \) (with gA = 1.25) to the axial current; indeed simple Pauli matrix algebra gives then:
$$\sum\limits_n {\left\{ {{{\left| { < n\left| {\sum \sum\limits_i^A {{g_A}\sigma _i^2\tau _i^ + } } \right|0 > } \right|}^2} - {{\left| {n\left| {\sum\limits_i^A {{g_A}\sigma _i^2\tau _i^ - } } \right|0 > } \right|}^2}} \right\}} = (N - Z)g_A^2$$
(1)
In principle, both the positively and negatively charged branches have to be measured; in a nucleus with positive neutron excess however, equation (1) gives already a lower limit for the σ τ+ strength which is the quantity accessible through (p,n) reactions and Pauli blocking rapidly suppresses the T- branch as (N-Z) increases. Thus, if one assumes that no part of the strength has escaped detection, a reduction such as that observed in a wide range of nuclei is strongly suggestive of the intervention of new degrees of freedom.

Keywords

Axial Current Pauli Blocking Pion Pole Axial Vector Coupling Average Nuclear Density 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1984

Authors and Affiliations

  • J. Delorme
    • 1
  • M. Ericson
    • 1
  • A. Figureau
    • 1
  • N. Giraud
    • 1
  1. 1.Institut de Physique NucléaireUniversité Claude BernardVilleurbanne CedexFrance

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