Lorentz-Lorenz Quenching for the Gamow-Teller Sum Rules

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


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:
$$\sum\limits_n {\left\{ {{{\left| { < n\left| {\sum \sum\limits_i^A {{g_A}\sigma _i^2\tau _i^ + } } \right|0 > } \right|}^2} - {{\left| {n\left| {\sum\limits_i^A {{g_A}\sigma _i^2\tau _i^ - } } \right|0 > } \right|}^2}} \right\}} = (N - Z)g_A^2$$
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.


Axial Current Pauli Blocking Pion Pole Axial Vector Coupling Average Nuclear Density 
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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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