Production of ${\pi }^{+}$ and ${\pi }^{-}$ at Large Transverse Momentum in $p-p$ and $p-d$ Collisions at 200, 300, and 400 GeV

We have measured the production of ${\pi }^{+}$ and ${\pi }^{-}$ in 200-, 300-, and 400-GeV $p-p$ and 400-GeV $p-d$ collisions for transverse momenta ($p_{\perp }$) ranging from 0.77 to 7.67 GeV/c. At large values of $x_{\perp }=\frac{2p_{\perp }}{\sqrt{s}}$, where $\sqrt{s}$ is the c.m. energy, we have fitted the $p-p$ data to the form $A{(1-x_{\perp })}^b{p_{\perp }}^{-n}$; we obtain $n=8.2\mathrm{}\pm 0.5$ for ${\pi }^{+}$ and 8.5±0.5 for ${\pi }^{-}$. At $x_{\perp }>0.3\mathrm{}$ the $\frac{{\pi }^{+}}{{\pi }^{-}}$ ratio in $p-p$ collisions rises appreciably with increasing $x_{\perp }$ whereas the $\frac{{\pi }^{+}}{{\pi }^{-}}$ ratio obtained from the difference of $p-d$ and $p-p$ cross sections is ∼ 1.0 at all $x_{\perp }$.