Abstract
We have measured the branching ratios for\(\bar pp\) annihilation at rest intoπ + π − η andπ + π − η′ in hydrogen gas in two data samples that have different fractions ofS-wave andP-wave initial states. The branching ratios are derived from a comparison with the topological branching ratio for\(\bar pp\) annihilations into four charged pions of (49±4)% and the branching ratio intoπ + π − π + π − π 0 of (18.7±1.6)%. We find a significant reduction of the branching ratios fromP-states for\(\bar pp \to \pi ^ + \pi ^ - \eta \) andπ + π − η′ in comparison toS-state annihilation.
In a partial wave analysis of theπ + π − η Dalitz plot we find the following contributions: Phase space,\(a_2^ + (1320)\pi ^ \mp \),ηρ0 andf 2(1270)η:
We find a 2 σ effect for the reaction\(\bar pp \to a_0^ \pm (980)\pi ^ \mp \),\(a_0^ \pm \to \eta \pi ^ \pm \), with a branching ratio of (0.13±0.07)·10−3. For η' production we give a branching ratio of\(\bar pp \to \rho \eta '\) of (1.81±0.44)·10−3 from3 S 1. We estmate a contribution of about 0.3·10−3 for ρη' fromP-states. The ratio of ρη and ρη' rpoduction is used to test the validity of the quark line rule. In theπ + π − π + π − γ final state we do not observe the reaction\(\bar pp \to \pi ^ + \pi ^ - \omega \) , ω→π + π − λ and derive an upper limit of 3·10−3 for decay modeω→π + π − λ.
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This work comprises part of the thesis of P. Weidenauer
Part of this work was done while
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ASTERIX Collaboration., Weidenauer, P., Duch, K.D. et al. Antiproton-proton annihilation at rest intoπ + π − η ′ andπ + π − η from atomicS andP states. Z. Phys. C - Particles and Fields 47, 353–365 (1990). https://doi.org/10.1007/BF01565858
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DOI: https://doi.org/10.1007/BF01565858