Difficulties in the description of Drell-Yan processes at moderate invariant mass and high transverse momentum

We study the Drell-Yan cross section differential with respect to the transverse momentum of the produced lepton pair. We consider data with moderate invariant mass Q of the lepton pair, between 4.5 and 13.5 GeV, and similar (although slightly smaller) values of the transverse momentum q(T). We approach the problem by deriving predictions based on standard collinear factorization, which are expected to be valid toward the high-q(T) end of the spectrum and to which any description of the spectrum at lower q(T) using transverse-momentum dependent parton distributions ultimately needs to be matched. We find that the collinear framework predicts cross sections that in most cases are significantly below available data at high q(T). We discuss additional perturbative and possible nonperturbative effects that increase the predicted cross section, but not by a sufficient amount.