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 less than or equal to y less than or equal to 3.3 and transverse momentum region of 0.075 GeV/c less than or equal to p(T) less than or equal to 1,025 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.