High-statistics study of the reaction γp → p2π0

Abstract

The photoproduction of 2π0 mesons off protons was studied with the Crystal Barrel/TAPS experiment at the electron accelerator ELSA in Bonn. The energy of photons produced in a radiator was tagged in the energy range from 600 MeV to 2.5 GeV. Differential and total cross sections and pπ0π0 Dalitz plots are presented. Part of the data was taken with a diamond radiator producing linearly polarized photons, and beam asymmetries were derived. Properties of nucleon and Δ resonances contributing to the pπ0π0 final state were determined within the Bonn-Gatchina (BnGa) partial-wave analysis. The data presented here allow us to determine branching ratios of nucleon and Δ resonances for their decays into pπ0π0 via several intermediate states. Most prominent are decays proceeding via Δ(1232)π, N(1440)1/2+π, N(1520)3/2−π, N(1680)5/2+π, but also pf0(500), pf0(980), and pf2(1270) contribute to the reaction.