Pion Correlations and Resonance Effects in ppbar Annihilation to 4pi0 at   Rest
  We study pi0pi0 correlations in the exclusive reaction ppbar -> 4pi0 at rest with complete reconstruction of the kinematics for each event. The inclusive distribution shows a dip at small invariant mass of the pion pair while a small enhancement in the double differential distribution is observed for small invariant masses of both pion pairs. Dynamical models with resonances in the final state are shown to be consistent with the data while the stochastic HBT mechanism is not supported by the present findings. 
O. Kortner, M.P. Locher, V.E. Markushin, P. Weber, O. Wigger