Two-photon production of final states with ap $\bar p$ pair

Abstract

Two-photon production of the exclusive final statesp $\bar p$+nπ (n=0, 1, 2, and 3) has been investigated using the ARGUS detector at thee ⁺ e ⁻ storage ring DORIS II at DESY. The reactionsγγ→p $\bar p$ π andγγ→p $\bar p$ π ⁺ π ⁻ π ⁰ have been observed for the first time, as have theΔ ⁺⁺ and$\overline {\Delta ^{ + + } }$ baryons in the final statep $\bar p$ π ⁺ π ⁻. No evidence was found forΔ ⁺⁺ $\overline {\Delta ^{ + + } }$ production. Topological cross sections for two-photon production ofp $\bar p$,p $\bar p$ π ⁰,p $\bar p$ π ⁺ π ⁻ andp $\bar p$ π ⁺ π ⁻ π ⁰, as well as the crosssection forγγ→Δ ⁺⁺ $\bar p$ π ⁺ π ⁻+c.c., have been measured. Upper limits are given for the cross section forγγ→Δ ⁰ $\overline {\Delta ^0 }$,γγ→Δ ⁺⁺ $\overline {\Delta ^{ + + } }$ andγγ→Λ $\bar \Lambda$.