Energy-Dependence Of Charged Pions Produced At 180-Degrees In 0.8-4.89-Gev Proton-Nucleus Collisions

High-energy charged pions produced at 180\ifmmode^\circ\else\textdegree\fi{} in 0.8-4.89-GeV proton-nucleus collisions have been studied. Both the slopes of the energy spectra and the $\frac{{\ensuremath{\pi}}^{\ensuremath{-}}}{{\ensuremath{\pi}}^{+}}$ ratios increase rapidly with primary energy up to \ensuremath{\sim} 3-4 GeV, where limiting values appear to be reached. The dependence on target mass also changes over this energy range. Unlike forward pion-production results, backward pions at these energies do not obey the scaling law suggested by Schmidt and Blankenbecler.