  Deuteron production in S and Pb induced collisions at beam energies of 200
and 160 AGeV is studied in the framework of the transport theoretical approach
RQMD. Strong transverse flow invalidates the differential coalescence formula
in momentum space. The transverse momentum integrated $d$ yields scale in a
broad rapidity interval with the squared proton densities and inversely with
the produced particle rapidity densities. This kind of scaling can be linked to
constant relative sizes of nucleon and pion sources at freeze-out. With
increasing projectile mass the nucleon source blows up stronger than the pion
source. As a result, the scaled deuteron densities drop in central Pb+Pb
collisions by 15 percent as compared to S induced reactions.
