### Abstract

We have determined branching ratios for antiproton annihilations at rest on protons or neutrons in liquid deuterium which we compare to frequencies of isospin-related processes in antiproton-proton annihilations. Using the annihilation rates into π^{0}π^{0} and π^{-}π^{0} where the annihilation took place on the proton or neutron, respectively, we discuss the fraction of S-wave and P-wave annihilation in liquid D_{2}. The frequencies for π^{-}ω and ρ^{-}π^{0}, and π^{-}η and π^{-}η′ and the corresponding frequencies for p̄p annihilations are used to determine isoscalar and isovector contributions to the protonium wave function. The isospin decomposition of the annihilating p̄p system in the ^{3}S_{1} or ^{1}S_{0} state is consistent with both, pure p̄p initial wave function and with the predictions of N̄N potential models. For the ^{3}P_{0} state of the p̄p atom we find consistency with a pure p̄p system at annihilation while N̄N potential models predict large n̄n contributions. We observe ρ-ω interference in p̄p→ π^{+}π^{-}η and π^{+}π^{-}π^{0} annihilation which we compare to ρ-ω interference in e^{+}e^{-} annihilation. The interference patterns show striking similarities due to similar phase relations; the interference magnitude depends on the ω-ρ production ratio. The similarity of the phase in all 3 data sets demonstrates that isovector and isoscalar parts of the protonium (p̄p atomic) wave function are relatively real, again in conflict with N̄N potential models. The annihilation rate for p̄d→K^{-}K^{0}p confirms the dominance of the isovector contribution to N̄N→ KK̄ annihilations. No complications due to initial state interactions are required by the data. Furthermore, we searched for narrow quasinuclear bound states close to the N̄N threshold, also predicted by NN potential models, but with negative outcome. We conclude that N̄N potential models are not suited to provide insight into the dynamics of the annihilation process.

Original language | English |
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Pages (from-to) | 583-592 |

Number of pages | 10 |

Journal | European Physical Journal C |

Volume | 17 |

Issue number | 4 |

Publication status | Published - Dec 1 2000 |

### ASJC Scopus subject areas

- Engineering (miscellaneous)
- Physics and Astronomy (miscellaneous)

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## Cite this

*European Physical Journal C*,

*17*(4), 583-592.