We have measured the differential and total cross sections and polarization of the ${\Sigma }^0$ from the reaction ${\pi }^{-}+p\to {\Sigma }^0+K^0$ with 1170-MeV/c pions incident on the Alvarez 72-in. hydrogen bubble chamber. Using 524 single-$\Lambda$ events (where the only visible decay is that of the $\Lambda$ from the decay ${\Sigma }^0\to \Lambda +\gamma$), 138 single-$K^0$ events (where only the $K^0$ decay is visible), and 256 double-vee events (where both $\Lambda$ and $K^0$ decays are visible), we find the coefficients in the Legendre expansion of the differential cross section $\frac{d\sigma }{d\Omega }=A_0{P}_0+A_1{P}_1+A_2{P}_2$ to be $A_0=19.68\mathrm{}\pm 0.60$ μb/sr, $A_1=-0.04\mathrm{}\pm 1.20$ μb/sr, and $A_2=14.54\mathrm{}\pm 1.60$ μb/sr, corresponding to a total cross section $\sigma =247\mathrm{}\pm 10$ μb. No polynominals higher than $P_2$ are needed. Using both single-$\Lambda$ and double-vee events, we find the coefficients in the polarization expansion $P_{\Sigma }\frac{d\sigma }{d\Omega }=\frac{1}{2}{sin\theta }_{\Sigma }(B_1+B_2{cos\theta }_{\Sigma })$ to be $B_1=-9.98\mathrm{}\pm 8.29$ μb/sr and $B_2=-35.45\mathrm{}\pm 21.88$ μb/sr. In both angular-distribution and polarization studies a single-$\Lambda$ event is statistically equivalent to about one half of a double-vee event.

• Received 22 June 1966

DOI:https://doi.org/10.1103/PhysRev.152.1139