Leading baryon production in p+A collisions at relativistic energies

Invariant multiplicity distributions of the leading neutron and proton have been measured in minimum bias p + Be, p + Al, p + Cu, and p + Pb collisions at 19 GeV/c and p + Be and p + Pb collisions at 12 GeV/c with the E864/E941 spectrometer at the Alternating Gradient Synchrotron (AGS). The experimental acceptance for the measurement covers a rapidity region of 1.7.3 and transverse momentum region of 0.075 GeV/c T.025 GeV/c. The leading proton and leading neutron production, as a function of the light cone momentum fraction x +, show energy scaling at AGS energies. The proton/neutron ratio, (dN/dx +) p/(dN/dx +) n, decreases from about 5.0 near beam rapidity to about one at midrapidity. The ratio has no strong target dependence as a function of rapidity. The target dependence of the leading proton distribution as a function of x + demonstrates an approximate energy scaling from the AGS to the Super Proton Synchrotron.