Chiral perturbation theory for pentaquark baryons and its applications

Abstract We construct a chiral Lagrangian for pentaquark baryons assuming that the recently found Θ + ( 1540 ) state belongs to an antidecuplet of SU ( 3 ) flavor symmetry with J P = 1 2 ± . We derive the Gell-Mann–Okubo formulae for the antidecuplet baryon masses, and a possible mixing between the antidecuplet and the pentaquark octet. Then we calculate the cross sections for π − p → K − Θ + and γ n → K − Θ + using our chiral Lagrangian. The resulting amplitudes respect the underlying chiral symmetry of QCD correctly. We also describe how to include the light vector mesons in the chiral Lagrangian.