s-wave pion nucleon scattering lengths from πN, pionic hydrogen, and deuteron data -: art. no. 045203

The isoscalar and isovector scattering lengths (b(0),b(1)) are determined using a unitarized coupled channel approach based on chiral Lagrangians. Using experimental values of pionic hydrogen and deuterium as well as low energy piN scattering data, the free parameters of the model are calculated. Isospin violation is incorporated to a certain extent by working with physical particle masses. For the deuterium scattering length a(pi)(-)d new significant corrections concerning real and imaginary parts are evaluated, putting new constraints from pi(-)d scattering on the values of (b(0),b(1)). In particular, dispersion corrections, the influence of the Delta(1232) resonance, crossed terms and multiple scattering in a Faddeev approach are considered.