Pentaquark image production from photon–nucleon reactions Original Research Article

Pentaquark Θ+ baryon production from photon–nucleon reactions is studied in a hadronic model that uses empirical hadron masses and coupling constants as well as includes both KNΘ and K*NΘ couplings. Taking gKNΘ=3.0 corresponding to a Θ+ width of 9 MeV, gK*NΘ=gKNΘ, and a cutoff parameter Λ=1.2 GeV in form factors, both the Θ+ total production cross section and angular distribution are evaluated. For the reaction View the MathML source, the total cross section for producing a positive parity Θ+ is about 300 nb at photon energy Eγ=3 GeV, comparable to the quoted cross section from the SAPHIR experiment at Bonn Electron Stretcher Accelerator. The cross sections for the other reactions γn→K−Θ+, View the MathML source, and γn→K*−Θ+ at Eγ=3 GeV are about 250 nb, 125 nb, and 1350 nb, respectively, if the parity of Θ+ is positive. The angular distributions of produced Θ+ in these reactions all peak at forward angles. For negative parity Θ+, the total cross sections for these reactions are reduced by more than an order of magnitude, while their angular distributions remain forward peaked.