Abstract
Abstract The reaction p p → p p ω was investigated with the TOF spectrometer, which is an external experiment at the accelerator COSY (Forschungszentrum Julich, Germany). Total as well as differential cross sections were determined at an excess energy of 93 MeV ( p beam = 2950 MeV / c ). Using the total cross section of ( 9.0 ± 0.7 ± 1.1 ) μb for the reaction p p → p p ω determined here and existing data for the reaction p p → p p ϕ , the ratio R ϕ / ω = σ ϕ / σ ω turns out to be significantly larger than expected by the Okubo–Zweig–Iizuka (OZI) rule. The uncertainty of this ratio is considerably smaller than in previous determinations. The differential distributions show that the ω production is still dominated by S-wave production at this excess energy, however higher partial waves clearly contribute. A comparison of the measured angular distributions for ω production to published distributions for ϕ production at 83 MeV shows that the data are consistent with an identical production mechanism for both vector mesons.
Highlights
Near-threshold production of the isoscalar vector mesons, ω and φ, in protonproton interactions remained largely unstudied until the late 1990s
Where c parametrizes the strength of the OZI-violation and ∆θV = 3.7◦ is the deviation from the ideal mixing angle
The cross sections presented in this paper extend and improve the experimental data base for the reaction pp → ppω at ǫ = 93 MeV
Summary
Near-threshold production of the isoscalar vector mesons, ω and φ, in protonproton interactions remained largely unstudied until the late 1990s. A considerable interest from theory arose [4,5,6,7,8,9], addressing the question of reaction dynamics, of possible proton-vector meson resonances, and of in-medium effects of vector meson properties Another important question is a possible ss content of the nucleon wave function, which may be determined through the ratio of the total cross sections of ω and φ mesons in proton-proton collisions at identical excess energies (Rφ/ω = σpp→ppφ/σpp→ppω). It is in agreement with our result of (7.5 ± 1.5 ± 1.9) μb published in Ref. [2], with improved accuracy
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