In almost all direct detection articles (see for example Jungman, G., Kamionkowski, M. & Griest, K., 1996. Supersymmetric dark matter) I found the following parametrization for the matrix element of the quark axial-vector coupling:(adsbygoogle = window.adsbygoogle || []).push({});

$$

\langle n|\bar q\gamma_\mu\gamma_5q|n\rangle=2s_\mu^{(n)}\Delta q^{(n)}

$$

where ##\Delta q## is the fraction of the nucleon spin carried by quark ##q## and ##s_\mu^{(n)}## is the spin of the nucleon ##n##. Even if this make sense i would like to have a reference where find a derivation or a justification of this fact.

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Quark axial-vector current in nucleion

**Physics Forums | Science Articles, Homework Help, Discussion**