Dynamics of 1S0 diproton formation in the reactions pp-> (pp)_s+pi0$ and pp-> (pp)_s+gamma in the GeV region

Abstract

COSY-ANKE data on the cross section of the reactions $pp\to \{pp{\}}_s{\pi }^0$ and $pp\to \{pp{\}}_s\gamma$, where $\{pp{\}}_s$ is the proton pair in the ${}^1{S}_0$ state at small excitation energy $E_{pp}<3$ MeV, are analyzed at beam energies $0.5-2.0$ GeV within the one-pion exchange model. The model includes the subprocesses ${\pi }^{0}p\to {\pi }^{0}p$ and ${\pi }^{0}p\to \gamma p$ for the pion- and photo-production, respectively, and accounts for the final state pp-interaction. A broad maximum in the energy dependence of the ${\pi }^0$ production at $\sim 0.5-0.6$ GeV and fast increase of the $\gamma$-production cross section at $0.3-0.55$ GeV observed in the data are explained by the $\Delta$-isobar contribution. An analogy with the dynamics of the deuteron breakup reaction $pd\to \{pp{\}}_{s}n$ in the $\Delta$-region is outlined.

Comments: 6 pages, 4 figures, Talk given at XIX International Baldin Seminar on High Enegy Physics Problems (Dubna, 29 September-4 October, 2008)