The quasi-free pn->dphi reaction has been studied at the Cooler Synchrotron COSY-Juelich, using the internal proton beam incident on a deuterium cluster-jet target and detecting a fast deuteron in coincidence with the K+K- decay of the phi-meson. The energy dependence of the total and differential cross sections are extracted for excess energies up to 80 MeV by determining the Fermi momentum of the target neutron on an event-by-event basis. Though these cross sections are consistent with s-wave production, the kaon angular distributions show the presence of p waves at quite low energy. Production on the neutron is found to be stronger than on the proton but not by as much as for the eta-meson.
Differential cross section dependence on the angle of the K+ from the PHI decay in the PHI rest frame.
Differential cross section dependence on the polar angle of the PHI in the overall rest frame.
Total cross section as a function of the excess energy.
The pp->pp phi reaction has been studied at the Cooler Synchrotron COSY-Juelich, using the internal beam and ANKE facility. Total cross sections have been determined at three excess energies epsilon near the production threshold. The differential cross section closest to threshold at epsilon=18.5 MeV exhibits a clear S-wave dominance as well as a noticeable effect due to the proton-proton final state interaction. Taken together with data for pp omega-production, a significant enhancement of the phi/omega ratio of a factor 8 is found compared to predictions based on the Okubo-Zweig-Iizuka rule.
K+ K- invariant mass distribution.
Total cross sections.
Differential decay distribution of the K+ in the rest frame of the PHI-meson w.r.t. the beam.
The reaction pp->d K+ Kbar0 has been investigated at an excess energy of Q=46 MeV above the (K+ Kbar0) threshold with ANKE at COSY-Juelich. From the detected coincident dK+ pairs about 1000 events with a missing Kbar0 were identified, corresponding to a total cross section of sigma(pp->d K+ Kbar0)=(38 +/- 2(stat) +/- 14(syst)) nb. Invariant-mass and angular distributions have been jointly analyzed and reveal s-wave dominance between the two kaons, accompanied by a p-wave between the deuteron and the kaon system. This is interpreted in terms of a0+(980)-resonance production.
Total cross section for P P --> DEUT K+ KBAR0.
Centre of mass angular distribution of the deuteron with respect to the direction of the incoming proton.
Centre of mass angular distribution of the vector joining the K+ and KBAR0 with respect to the direction of the incoming proton.
Excitation functions of proton-proton elastic scattering cross sections have been measured in narrow steps for projectile momenta pp (energies Tp) from 1100 to 3300MeV/c (500 to 2500 MeV) in the angular range 35°≤Θc.m.≤90° with a detector providing ΔΘc.m.≈1.4° resolution. Measurements have been performed continuously during projectile acceleration in the cooler synchrotron COSY with an internal CH2 fiber target, taking particular care to monitor luminosity as a function of Tp. The advantages of this experimental technique are demonstrated, and the excitation functions obtained are compared to existing cross section data. No evidence for narrow structures was found.
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π−-photoproduction cross sections from neutrons have been measured with a deuterium target at effective γ-energies from 900 to 1,800 MeV and pion centre-of-mass angles 65 to 125°. The outgoing pion and proton were detected in coincidence, the pion with a magnetic spectrometer and the proton with a time-of-flight system. To test the reliability of the analysis method, a comparison of π+-photoproduction from protons and deuterons was made with a slightly modified apparatus. It was found adequate to use the spectator model with a Huthèn wave function.
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Quasielastic e-d scattering measurements were performed up to q 2 = 100 fm −2 . Only the electron was detected. The ratio R= ( d 2 ω d Ω d E′) ed d ω d Ω) ep was measured at the quasielastic peak; the magnetic form factor G M N of the neutron was deduced using the assumption G E N = 0.
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CONST(NAME=MU) is the magnetic moment. The magnetic formfarctor (GM) is evaluated ander assumption of GE=0.
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The reaction γ+p→π++n has been investigated for photon energies between 1.2 and 3 GeV and pion c.m. angles from 2.5 to 15°. The cross section is strongly peaked in the forward direction and shows resonance structure in the region of the N32*(1920) and N12*(2190).
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Differential cross sections for the reaction γ+p→n+π+ are presented for incident photon energies between 1.2 and 3 GeV and pion center-of-mass production angles of 15 to 50 deg.
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