We have studied how lepton pairs from decays of heavy-flavoured mesons produced in pA collisions can be used to determine the modifications of the gluon distribution in the nucleus. Since heavy quark production is dominated by the gg channel, the ratio of correlated lepton pair cross sections from DD-bar and BB-bar decays in pA and pp collisions directly reflects the ratio R_gA= f_gA/f_gp. We have numerically calculated the lepton pair cross sections from these decays in pp and pA collisions at SPS, RHIC and LHC energies. We find that ratio of the pA to pp cross sections agrees quite well with the input R_gA. Thus, sufficiently accurate measurements could be used to determine the nuclear modification of the gluon distribution over a greater range of x and Q2 than presently available, putting strong constraints on models.

When nonlinear effects on the gluon evolution are included with constraints from HERA, the gluon distribution in the free proton is enhanced at low momentum fractions, x\leq 0.01, and low scales, Q2\lsim 10 GeV2, relative to standard, DGLAP-evolved, gluon distributions. Consequently, such gluon distributions can enhance charm production in pp collisions at center of mass energy 14 TeV by up to a factor of five at midrapidity, y\sim0, and transverse momentum p_T\rightarrow0 in the most optimistic case. We show that most of this enhancement survives hadronization into D mesons. Assuming the same enhancement at leading and next-to-leading order, we show that the $D$ enhancement may be measured by D0 reconstruction in the K-pi+ decay channel with the ALICE detector.