On the production of [FORMULA][FORMULA] pairs in pp collisions at 0.8 GeV

Data accumulated recently for the exclusive measurement of the pp[FORMULA]pp[FORMULA][FORMULA] reaction at a beam energy of 0.793GeV using the COSY-TOF spectrometer have been analyzed with respect to possible events from the pp[FORMULA]nn[FORMULA][FORMULA] reaction channel. The latter is expected to be the only [FORMULA][FORMULA] production channel, which contains no major contributions from resonance excitation close to threshold and hence should be a good testing ground for chiral dynamics in the [FORMULA][FORMULA] production process. No single event has been found, which meets all conditions for being a candidate for the pp[FORMULA]nn[FORMULA][FORMULA] reaction. This gives an upper limit for the cross-section of 0.16μb (90% C.L.), which is more than an order of magnitude smaller than the cross-sections of the other two-pion production channels at the same incident energy.