  The high statistics data from the pp -> ppeta reaction measurement, delivered
by the COSY-11 collaboration, are now being evaluated using the correlation
femtoscopy technique. This method is based on the relative momentum
correlations of two emitted protons and may permit determination of the size of
the reaction volume. For the very first time, we apply an intensity
interferometry technique to study the mechanism of the meson production via the
nucleon-nucleon interaction close to the kinematical threshold. We invented a
method to determine correlation function for the ppeta system free from the
physical multi-pion production background. We show the comparison of
experimental results with theoretical predictions and appraise the accuracy
achieved for the determination of the size of the emission source.
