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HK: Hadronen und Kerne

HK 49: Hadronic Probes V, Particle Production

HK 49.2: Group Report

Wednesday, March 18, 1998, 14:30–15:00, C

Near Threshold φ and ω Meson Production and the Strangeness Content of the Nucleon — •J. Ritman — II. Physikalisches Institut, Heinrich-Buff-Ring 16, Universität Gießen, D-35392 Gießen

Recently a very sharp rise in the relative yield of the φ meson compared to the ω meson has been observed in pp annihilation at rest in channels with large S-wave contributions. A widely discussed explanation of this enhancement over predictions based on the Okubo-Zweig-Iizuka (OZI) rule requires a significant contribution of strange quarks to the proton’s wave function. Indeed studies of the proton’s spin structure via deep inelastic scattering indicate around 10-20% ss contribution to the proton (albeit at a different value of q²). Based on symmetry arguments it is important to determine if a similar enhancement is observed in near threshold proton-proton reactions where the S-wave also dominates. Therefore the DISTO spectrometer at Saclay has been used to measure the φ/ω ratio in kinematically complete exclusive reactions of the type pp → ppφ → ppK⁺K⁻ and pp → ppω → pp π⁺ π⁻ (π^∘ missing) produced by a polarized proton beam at 2.85 GeV. The φ/ω ratio determined here will be presented and discussed in the context of the nucleon’s strangeness content.
This work is in part supported by GSI and IN2P3