Obtaining the nuclear gluon distribution from heavy quark decays to lepton pairs in pA collisions

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 D(D)over bar and B(B)over bar decays in pA and pp collisions directly reflects the ratio R-g(A) drop f(g)(A). 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-g(A). Thus, sufficiently accurate measurements could be used to determine the nuclear modification of the gluon distribution over a greater range of x and Q(2) than presently available, putting strong constraints on models. (C) 2001 Elsevier Science B.V. All rights reserved.