Production ofΣ+Hyperons by 990-Mev Positive Pions in Liquid Hydrogen

The production and subsequent decay of six ${\Sigma }^{+}$ hyperons was observed in the central region of a hydrogen bubble chamber exposed to ${\pi }^{+}$ mesons of kinetic energy 990±30 Mev at the Cosmotron. The corresponding total production cross section, corrected for scanning inefficiencies, is ${0.16}_{-0.06\mathrm{}}^{+0.08\mathrm{}}$ mb. This value, combined with weighted averages of ${\Sigma }^0$ and ${\Sigma }^{-}$ production cross sections in hydrogen obtained by Brookhaven, Columbia, and Berkeley groups, is used to compute the three triangular inequalities imposed by charge independence. The inequality ${\left[\sigma \right({\Sigma }^{+}\left)\right]}^{\frac{1}{2}}+{\left[\sigma \right({\Sigma }^{-}\left)\right]}^{\frac{1}{2}}-{\left[2\mathrm{}\sigma \right({\Sigma }^0\left)\right]}^{\frac{1}{2}}={{0.12}_{-0.10\mathrm{}}}^{+0.11\mathrm{}}{\left(\mathrm{mb}\right)}^{\frac{1}{2}}\geqq 0$ is the only one that might not be satisfied. The near-zero value of the left-hand side indicates the difficulty to be encountered in demonstrating a failure of charge independence at this energy.