The Partonic Content of $h_1(x)$ and $h_2(x)
  A light-cone wavefunction interpretation is presented for the polarized distribution functions $h_1(x)$ and $h_2(x)$. All matrix elements for moments of these distributions are given in terms of overlap integrals between Fock state amplitudes of the target state. In a suitable spinor basis, $h_1(x)$ involves only diagonal matrix elements so can be interpreted as a density. Matrix elements of $h_2(x)$ connect Fock states differing by one gluon so that $h_2(x)$ has no simple interpretation as a density. Nevertheless, in the wavefunction decomposition, $h_2(x)$ is described through a compact set of elementary quark-gluon processes which are averaged over the target wavefunction. 
Arjun Berera