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 $p+\mathrm{Be},$ $p+\mathrm{Al},$ $p+\mathrm{Cu},$ and $p+\mathrm{Pb}$ collisions at $19 \mathrm{GeV}/c$ and $p+\mathrm{Be}$ and $p+\mathrm{Pb}$ collisions at $12 \mathrm{GeV}/c$ with the E864/E941 spectrometer at the Alternating Gradient Synchrotron (AGS). The experimental acceptance for the measurement covers a rapidity region of $1.7<~y<~3.3$ and transverse momentum region of $0.075 \mathrm{GeV}/c$ $<~{p}_{T}<~1.025 \mathrm{GeV}/c.$ 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.