Lineshape of the Λ(1405) hyperon measured through its Σ0π0 decay

The differential and total cross sections for the dp{yields}{sup 3}He{eta} reaction have been measured in a high precision high statistics COSY-ANKE experiment near threshold using a continuous beam energy ramp up to an excess energy Q of 11.3 MeV with essentially 100% acceptance. The kinematics allowed the mean value of Q to be determined to about 9 keV. Evidence is found for the effects of higher partial waves for Q > or approx. 4 MeV. The very rapid rise of the total cross section to its maximum value within 0.5 MeV of threshold implies a very large {eta}{sup 3}He scattering length and hence the presence of a quasibound state extremely close to threshold.

https://arxiv.org/pdf/nucl-ex/0701072.pdf

Precision study of the eta He-3 system using the dp ---> He-3 eta reaction

Measurement of the in-medium ϕ-meson width in proton–nucleus collisions

The differential and total cross sections for kaon pair production in the pp -> ppK(+)K(-) reaction have been measured at three beam energies of 2.65, 2.70, and 2.83 GeV using the ANKE magnetic spectrometer at the COSY-Julich accelerator. These near-threshold data are separated into pairs arising from the decay of the phi-meson and the remainder. For the non-phi selection, the ratio of the differential cross sections in terms of the K(-)p and K(+)p invariant masses is strongly peaked toward low masses. This effect can be described quantitatively by using a simple ansatz for the K(-)p final state interaction, where it is seen that the data are sensitive to the magnitude of an effective K(-)p scattering length. When allowance is made for a small number of phi events where the K- rescatters from the proton, the phi region is equally well described at all three energies. A very similar phenomenon is discovered in the ratio of the cross sections as functions of the K(-)pp and K(+)pp invariant masses and the identical final state interaction model is also very successful here. The world data on the energy dependence of the non-phi total cross section is also reproduced, except possibly for the results closest to threshold.

/pdf/kaon-pair-production-in-proton-proton-collisions-59o4bhuqqq.pdf

Kaon Pair Production in Proton-Proton Collisions

The pp ! ppreaction has been studied at the Cooler Synchrotron COSY-Julich, using the internal beam and ANKE facility. Total cross sections have been determined at three excess energiesnear the production threshold. The differential cross section closest to threshold at � � 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! production, a significant enhancement of the �=! ratio of a factor 8 is found compared to predictions based on the Okubo-Zweig-Iizuka rule.

Near-threshold production of phi mesons in pp collisions.

ANKE is a new experimental facility for the spectroscopy of products from proton-induced reactions on internal targets. It has recently been implemented in the accelerator ring of the cooler synchrotron COSY of the Forschungszentrum Julich (FZ-Julich), Germany. The device consists of three dipole magnets, various target installations and dedicated detection systems. It will enable a variety of hadron-physics experiments like meson production in elementary proton–nucleon processes and studies of medium modifications in proton–nucleus interactions.

A Selikov

Papers

ANKE, a new facility for medium energy hadron physics at COSY-Jülich