The reaction $\text{p}\text{p}\text{→}\text{p}\text{π}{}^{\mathrm{-}}\text{π}{}^{\mathrm{+}}\text{p}$ at 25 and 40 GeV/c

Abstract

The reaction $\text{p}\text{p}\text{→}\text{p}\text{π}{}^{\mathrm{-}}\text{π}{}^{\mathrm{+}}\text{p}$ has been studied at 25 and 40 GeV/c at the Serpukhov proton synchroton using the CERN-IHEP spectrometer. The differential cross section has been determined as a function of four-momentum transfer to the proton (0.05–0.30 (GeV/c)²) and $\text{p}\text{ππ}$ mass (up to 2.2 and 2.6 GeV/c²). At both energies there is a broad low-mass maximum with an enhancement at 1.6–1.8 GeV/c². The cross section in a given mass band falls rapidly with |t|, with an exponential slope that decreases with increasing mass. In both the background and the 1.7 GeV/c² peak there is a strong $\text{Δ}{}^{\mathrm{--}}\text{π}{}^{\mathrm{+}}$ component. Possible spin-parity (J^P) contributions to it are discussed. Throughout the range 1.5–2.2 GeV there is at least one state of $\text{J ⩾}\text{3}\text{2}$ and there is interference between states of opposite P, |ΔJ| ⩽ 1. At the peak there is a $\text{J ⩾}\text{5}\text{2}$ component. There are striking parallels between this reaction and the boson reactions π⁻p→π⁻π⁻π⁺p and K⁻ → K⁻π⁻π⁺p.