Charged particle and π⁰ multiplicity distributions and the annihilation properties of$\bar p$ p interactions at 70 GeV/c

Abstract

The elastic and inelastic$\bar p$ p cross sections at 70 GeV/c have been determined in an experiment performed at CERN using BEBC equipped with a TST. The topological cross sections were measured and the moments of the inelastic multiplicity distribution are 〈n _c 〉=6.16±0.09, 〈n _c 〉/D=2.04±0.05 andf ^cc₂ =2.97±0.03. The average number of Dalitz pairs per inelastic event is (3.12±0.09)×10⁻². Assuming that these all arise from π⁰ decay the average π⁰ multiplicity is$\langle n_{\pi ^0 } \rangle = 2.71 \pm 0.14$. The$\bar p$ p−pp cross section differences lead to an annihilation cross section σ _A = 4.42±0.41 mb and the moments of the annihilation multiplicty distribution are 〈n _A 〉=8.0±0.3, 〈n _A 〉/D=2.5±0.2 andf ^A−−₂ =−1.4±0.3. An independent check of σ _A was made by investigating fast forward charged and neutral secondary interactions in the TST and in the surrounding neon-hydrogen mixture, and gives a value σ _A = 5.0±1.6 mb. The ratio of fast$\bar n$ to$\bar p$ production in non-annihilation interactions at 70 GeV/c is found to be 0.45±0.11.