Andrea M.
- 27
- 1
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:
$$
\langle n|\bar q\gamma_\mu\gamma_5q|n\rangle=2s_\mu^{(n)}\Delta q^{(n)}
$$
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.
$$
\langle n|\bar q\gamma_\mu\gamma_5q|n\rangle=2s_\mu^{(n)}\Delta q^{(n)}
$$
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.