Pentaquark Theta(+) production from the reaction gamma p ->pi K-+(-)Theta(+)
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The cross section for theta(+) production from the reaction gammap-->pi(+)K(-)theta(+), which was observed in the CLAS experiment at the Jefferson National Laboratory, is evaluated in a hadronic model that includes couplings of theta(+) to both KN and K*N. With their coupling constants determined from the empirical piNN(1710) and rhoNN(1710) coupling constants using the SU(3) symmetry, the cross section for this reaction has been evaluated by taking theta(+) to have spin 1/2 and isospin 0 but either positive or negative parity. We find that if theta(+) has positive parity as predicted by the chiral soliton model and the correlated quark model, the cross section is 50-110 nb, depending on the value of the K*Ntheta coupling. The cross section is reduced by more than a factor of 10 if theta(+) has negative parity as given by lattice QCD studies and the uncorrelated quark model. For both parities, the differential cross section peaks at small negative four-momentum transfer when the reaction is dominated by the t-channel kaon-exchange diagram that involves only the coupling of theta(+) to KN. After decreasing with increasing negative four-momentum transfer, the differential cross section increases again when the u-channel contribution due to intermediate theta(+) propagation becomes important at large negative four-momentum transfer.
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