Dilepton angular distributions in the color-dipole S-matrix framework

A bstract The dilepton production at forward rapidities in hadronic collisions at the LHC energies is considered and the helicity density matrix elements of gauge bosons that enter the Drell-Yan angular coefficients associated with the gauge boson decay ( G = γ ∗ , Z 0 , W ) are derived using the color-dipole S -matrix framework. We show results for pp collisions at $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 14 TeV for the nonvanishing helicity density matrix elements in the rapidity range of 2.0 ≤ y ≤ 4.0 of the gauge boson. We consider different models for the proton unintegrated gluon distributions, among others a solution of the Balitsky-Kovchegov equation. We compare the associated predictions with those obtained disregarding the non-linear term in the evolution equation. In addition, the Lam-Tung relation is discussed.