Dispersion relations and analyticity constraints in (K)over-barN coupled channel analyses

We investigate the effects of introducing analyticity constraints in couple d channel analyses for the low-energy (K) over bar N sector. This is done b y studying amplitudes compatible, within the error bounds, with the solutio n from an existent effective-range M-matrix parametrization which covers da ta from the (K) over bar N threshold up to q = 550 MeV/c, and determining i f the values of the parameters of M, the coupling constants G(pi Lambda Sig ma)(2) and G(pi Sigma Sigma)(2) and the product G(pi Lambda Sigma)G(pi Sigm a Sigma) - extracted using un-subtracted fixed-t forward DR - differ for th ose amplitudes which fulfill the proposed analyticity constraints and those which are rejected by the same criteria. We also investigate the effects o f introducing constraints on the mass and width of the Lambda(1405) and Sig ma(1385) resonances and the stability of the parametrization.