  Among the physics goals of LHC experiments, precision tests of the Standard
Model in the Strong and Electroweak sectors play an important role. Because of
nature of the proton-proton processes, observables based on the measurement of
the direction and energy of leptons provide the most precise signatures. In the
present paper, we concentrate on the angular distribution of Drell-Yan process
leptons, in the lepton-pair rest-frame. The vector nature of the intermediate
state imposes that distributions are to a good precision described by spherical
polynomials of at most second order.
  We show that with the proper choice of the coordinate frames, only one
coefficient in this polynomial decomposition remains sizable, even in the
presence of one or two high $p_T$ jets. The necessary stochastic choice of the
frames relies on probabilities independent from any coupling constants.
  This remains true when one or two partons accompany the lepton pairs. In this
way electroweak effects can be better separated from strong interaction ones
for the benefit of the interpretation of the measurements.
  Our study exploits properties of single gluon emission matrix elements which
are clearly visible if a conveniently chosen form of their representation is
used. We rely also on distributions obtained from matrix element based Monte
Carlo generated samples of events with two leptons and up to two additional
partons in test samples. Incoming colliding protons' partons are distributed
accordingly to PDFs and are strictly collinear to the corresponding beams.
