# Figure 18

 Ratios of ($K^+$ + $K^-$) / ($\pi^+$ + $\pi^-$)(upper panel) and (p + $\rm\overline{p}$) / ($\pi^+$ + $\pi^-$) (lower panel) as a function of $\pt$ from pp collisions at $\sqrt{s}$ = 900 GeV (statistical errors only). Values from the E735Collaboration [36] and the STAR Collaboration [32] (upper part) and from the PHENIX Collaboration [41] (lower part) also are given. The dashed and dotted curves refer to calculations using PYTHIA and PHOJET at $\sqrt{s}$ = 900 GeV.