Experimental proton-proton correlation function derived for the pp -> ppeta reaction

Based on the high statistics data from the pp -> ppX reaction measured by the COSY-11 collaboration [1] we have derived a two-proton correlation function for the production of the ppeta and pp+pions systems. The measured correlation function normalized to the value simulated for a point-like source was compared with a theoretical prediction in order to estimate the size of the reaction volume.Comment: Talk given at the Symposium on Meson Physics at COSY-11 and WASA-at-COSY Krakow, Poland, 17-22 June 200

Study of the 3He−η^{3}He-\eta system in d-p collisions

We have measured excitation functions for the dp -> He-3 X, (X = pi(0),eta) channels near the eta production threshold. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target. The excitation function for the reaction dp -> He-3 pi(0) does not show any structure which could originate from the decay of He-3 - eta bound state. We measured also the threshold excitation curve for the dp -> He-3 X process, however, contrary to the SATURNE results, we observe no cusp near the eta threshold

Study of the 3He−η^{3}He-\eta system in d-p collisions

We have measured excitation functions for the d+p->3He+X, (X=pi0, eta) channels near the eta production threshold. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target. The excitation function for the reaction d+p->3He+pi0 does not show any structure which could originate from the decay of 3He-eta bound state. We measured also the threshold excitation curve for the d+p->3He+X process, however, contrary to the SATURNE results, we observe no cusp near the eta threshold.Comment: Talk given at 18th International IUPAP Conference on Few-Body Problems in Physics, 21-26 August, 2006, Santos, Brazil, 4 pages, 6 figures, will be published in Nuclear Physics

Isospin decomposition of the basic double-pionic fusion in the region ofthe ABC effect

Exclusive and kinematically complete high-statistics measurements of the basic double-pionic fusion reactions $pn\rightarrow d\pi ^{0}\pi ^{0}, pn\rightarrow d\pi ^{+}\pi ^{-}$ and $pp\rightarrow d\pi ^{+}\pi ^{0}$ have been carried out simultaneously over the energy region of the ABC effect using the WASA detector setup at COSY. Whereas the isoscalar reaction part given by the $d\pi ^{0}\pi ^{0}$ channel exhibits the ABC effect, i.e. a low-mass enhancement in the $\pi \pi$ - invariant mass distribution, as well as the associated resonance structure in the total cross section, the isovector part given by the $d\pi ^{+}\pi ^{-}$ channel shows a smooth behavior consistent with the conventional t -channel $\Delta \Delta$ process. The $d\pi^{+}\pi ^{-}$ data are very well reproduced by combining the data for isovector and isoscalar contributions, if the kinematical consequences of the isospin violation due to different masses for charged and neutral pions are taken into account