9 research outputs found
Study of the 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 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
Experimental study of pp eta dynamics in the pp -> pp eta reaction
A high statistics measurement of the pp-->ppeta reaction at an excess energy of Q=15.5 MeV has been performed at the internal beam facility COSY-11. The stochastically cooled proton beam and the used detection system allowed to determine the momenta of the outgoing protons with a precision of 4 MeV/c (sigma) in the center-of-mass frame. The determination of the four-momentum vectors of both outgoing protons allowed to derive the complete kinematical information of the etapp system. An unexpectedly large enhancement of the occupation density in the kinematical regions of low proton-eta relative momenta is observed. A description taking the proton-proton and the eta-proton interaction into account and assuming an on-shell incoherent pair-wise interaction among the produced particles fails to explain this strong effect. Its understanding will require a rigorous three-body approach to the ppeta system and the precise determination of contributions from higher partial waves. We also present an invariant mass spectrum of the proton-proton system determined at Q=4.5 MeV. Interestingly, the enhancement at large relative momenta between protons is visible also at such a small excess energy. In contrast to all other determined angular distributions, the orientation of the emission plane with respect to the beam direction is extracted to be anisotropic