Author/Authors :
F. H?rter، نويسنده , , J. Ahrens، نويسنده , , R. Beck، نويسنده , , B. Krusche and S. Schadmand، نويسنده , , V. Metag، نويسنده , , M. Schmitz، نويسنده , , H. Stroher، نويسنده , , Th. Walcher، نويسنده , , M. Wolf، نويسنده ,
Abstract :
The photoproduction of two neutral pions off the proton has been studied for incident photon energies between Eγ = 309 MeV (threshold) and 792 MeV with the TAPS photon spectrometer at the Mainz Microtron MAMI. Both 3γ- and 4γ-events have been analysed in order to deduce the total p(γ, 2π0)p cross section. The total cross section is less than 300 nb between threshold and ⋍ 460 MeV, beyond which it starts to rise to a maximum value of about 11 μb at around 750 MeV. For the highest energies it starts to decrease again. The 4γ-sample has been used to reconstruct 2 neutral pions from the above reaction channel by an invariant mass and a missing mass analysis. After reconstruction of the unobserved proton, a Dalitz-plot of mπ0π02vs. mpπ02 has been obtained, which indicates that the decay chain includes the Δ(1232)-resonance as an intermediate state.
