  We use the spinor helicity formalism to calculate the cross section for
production of three partons of a given polarization in Deep Inelastic
Scattering (DIS) off proton and nucleus targets at small Bjorken x. The target
proton or nucleus is treated as a classical color field (shock wave) from which
the produced partons scatter multiple times. We reported our result for the
final expression for the production cross section and studied the azimuthal
angular correlations of the produced partons in [1]. Here we provide the full
details of the calculation of the production cross section using the spinor
helicity methods.
