  Experimental data on analyzing power for inclusive meson and baryon
production in hadron-proton(polarized) collisions have been analyzed. It is
found that the existing data can be described by a simple function of collision
energy, transverse momentum (Pt) and a new scaling variable Xa = E/Ebeam. At
beam energies above 40 GeV and Pt above 1 GeV/c the analyzing power is
described by a function of Xa and Pt only (AN = F(Pt)G(Xa)) for both polarized
proton fragmentation and central regions of proton-hadron collision. Comparison
of data from Fermilab and new IHEP data measured using 40 GeV/c polarized
proton beam was most decisive for the revelation of the above regularities.
This new scaling law allows one to predict the analyzing powers for kinematic
regions, not yet explored in experiments and constrains models of strong
interactions. The new scaling law allows one also to use some reactions as
polarimeters for experiments with a polarized beam.
