Pentaquark Θ+ production from photon-nucleon reactions

Pentaquark Theta(+) 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 KNTheta and K*NTheta couplings. Taking g(KNTheta) = 3.0 corresponding to a Theta(+) width of 9 MeV, g(K*NTheta) = g(KNTheta), and a cutoff parameter Lambda = 1.2 GeV in form factors, both the Theta(+) total production cross section and angular distribution are evaluated. For the reaction yp --> (K) over bar (0)Theta(+), the total cross section for producing a positive parity Theta(+) is about 300 nb at photon energy E-gamma = 3 GeV, comparable to the quoted cross section from the SAPHIR experiment at Bonn Electron Stretcher Accelerator. The cross sections for the other reactions gamman --> K(-)Theta(+), gammap --> (K) over bar*(0)Theta(+), and gamman --> K*(-)Theta(+) at E-gamma = 3 GeV are about 250 nb, 125 nb, and 1350 nb, respectively, if the parity of Theta(+) is positive. The angular distributions of produced Theta(+) in these reactions all peak at forward angles. For negative parity Theta(+), the total cross sections for these reactions are reduced by more than an order of magnitude, while their angular distributions remain forward peaked. (C) 2004 Elsevier B.V. All rights reserved.