Abstrakt
We report on the investigation of Δ(1232) production and decay in proton-proton collisions at a kinetic energy of 1.25 GeV measured with HADES. Exclusive dilepton decay channels ppe+eMINUS SIGN and ppe+eMINUS SIGN γ have been studied and compared with the partial-wave analysis of the hadronic ppπ0 channel.
They allow to access both Δ+RIGHTWARDS ARROWpπ0(e+eMINUS SIGN γ) and Δ+RIGHTWARDS ARROWpe+eMINUS SIGN Dalitz decay channels. The perfect reconstruction of the well-known π0 Dalitz decay serves as a proof of the consistency of the analysis.
The Δ Dalitz decay is identified for the first time and the sensitivity to N-Δ transition form factors is tested. The Δ(1232) Dalitz decay branching ratio is also determined for the first time; our result is (4.19 +- 0.62 syst. +- 0.34 stat.) x10MINUS SIGN 5, albeit with some model dependence.