The reactionpp→ppπ+π−at205 GeVc

The reaction $\mathrm{pp}\to \mathrm{pp}{\pi }^{+}{\pi }^{-}$ is studied at $205 \frac{\mathrm{GeV}}{c}$ using the 30-in. bubble chamber at the National Accelerator Laboratory. The event selection is discussed in detail and the cross section is measured to be 0.68 ± 0.14 mb. This cross section is higher than one would expect based on a simple power-law extrapolation of lower-energy data. Peripheral production of a low-mass $p{\pi }^{+}{\pi }^{-}$ system dominates the reaction. The data are consistent with conservation of $t$-channel helicity.