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 (σ) 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 η pp system. An unexpectedly large enhancement of the …