Antiproton-proton annihilation at rest into two-body final states

Abstract

We report measurements of branching ratios for production of a series of two meson final states in$\bar p$ p annihilations at rest in liquid hydrogen. We find:

$$\begin{gathered} BR(\bar pp \to \pi ^ + \pi ^ - ) = (3.07 \pm 0.13) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to K^ + K^ - ) = (0.99 \pm 0.05) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to \pi ^0 \pi ^0 ) = (6.93 \pm 0.43) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \pi ^0 \eta ) = (2.12 \pm 0.12) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \pi ^0 \omega ) = (5.73 \pm 0.47) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to \pi ^0 \eta ') = (1.23 \pm 0.13) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \eta \eta ) = (1.64 \pm 0.10) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \eta \omega ) = (1.51 \pm 0.12) \cdot 10^{ - 2} \hfill \\ BR(\bar pp \to \eta \eta ') = (2.16 \pm 0.25) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \omega \omega ) = (3.32 \pm 0.34) \cdot 10^{ - 2} \hfill \\ BR(\bar pp \to \omega \eta ') = (0.78 \pm 0.08) \cdot 10^{ - 2} \hfill \\ \end{gathered}$$

These are the first measurements of the channels ηη′ and ωη′ and in almost all the other channels are more precise than previous results. We also obtain, in a more precise fashion, the following ratios of branching ratios:K ⁺ K ⁻/π⁺π⁻=0.323±0.013, π⁰η′/π⁰η=0.548±0.056, ηη′/ηη=0.31±0.15, ωη′/ωη=0.515±0.040, π⁰η/π⁰π⁰=0.303±0.010, ηη/π⁰π⁰=0.232±0.011 and π⁰ω/ηω=0.377±0.12. The measurements are made for different η and η′ decays, and we thus obtain Γ_η→3π ⁰/Γ_η→γγ=0.841±0.034, and$\Gamma _{\eta ' \to \gamma \gamma } /\Gamma _{\eta ' \to \pi ^0 \pi ^0 \eta } = 0.091 \pm 0.009$.