\pi^0 \pi^0 Production in Proton-Proton Collisions at Tp=1.4 GeV
  The reaction pp->pppi0pi0 has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324 +- 21_systematic +- 58_normalization) mub. In order to to study the production mechanism, differential kinematical distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate Delta(1232) resonances, each decaying into a proton and a single pion, thereby producing the pion pair in the final state. No significant contribution of the Roper resonance N*(1440) via its decay into a proton and two pions is found 
P. Adlarson, C. Adolph, W. Augustyniak, M. Bashkanov, T. Bednarski,   F.S. Bergmann, M. Ber{\l}owski, H. Bhatt, K.--T. Brink...
hep-ex