A possible interpretation of baryon spectrum with pentaquark components

The Lambda baryon spectrum is studied within the SU(3) flavor symmetry in a constituent quark model. We found that it is rather difficult to accommodate some negative-parity Lambda resonances as single q(2)s (q= u, d quarks) states in the conventional three-quark picture. The ground q(3)s (q) over bar pentaquark mass spectrum is evaluated and a possible interpretation is proposed in the work: the observed Lambda(1405)1/2(-), Lambda(1670)1/2(-) and Lambda(1800)1/2(-) are three-state mixtures of two p-wave q(2)s states and one ground q(3)s (q) over bar pentaquark state, so are the Lambda(1520)3/2(-), Lambda(1690)3/2(-) and Lambda(2050)3/2(-) resonances. Both Lambda(1405)1/2(-) and Lambda(1520)3/2(-) contain considerable q(3)s (q) over bar pentaquark components.