Interaction of eta Meson with Protons

P.Moskal für die COSY-11-Collaboration
Institute of Physics, Jagellonian University, ul. Reymonta 4, 30-059 Cracow, Poland

High statistics measurements of the pp->pp eta reaction at an excess energy of Q = 16 MeV have been performed at the internal facility COSY-11 installed at the cooler synchrotron COSY in Jülich. The measurement of four-momentum vectors for both outgoing protons of each registered event permits the full determination of all kinematical variables in the exit channel. The complete information of the eta pp-system allows to study the eta-proton interaction. The attractive interaction between eta-proton and proton-proton pairs suggests that a quasi-bound state may be formed in this three body system. The formation probability of such systems depends on a still not well established value of the eta-proton scattering length. The analysis of the data aims at determining both the real and imaginary part of this quantity.

First results of the elaboration of 15000 events will be presented and compared to the similar measurement performed parallel at the TOF spectrometer at COSY.