The leptonic current structure and azimuthal asymmetry in deeply inelastic scattering

We present a compact form of the leptonic currents for the computation of the processes involving an initial virtual boson (photon, $W^{\pm }$ or $Z_0$). For deeply inelastic scattering, once the azimuthal angle of the plane expanded by the initial- and final-state leptons are integrated over in the boson-proton rest frame, the azimuthal-asymmetric terms vanish, which, however, is NOT true when some physical quantities (such as the transverse momentum of the observed particle) are specified in laboratory frame. The abuse of the symmetry may lead to wrong results.