Strong and weak interactions in B→π+π−K decays

To describe the weak three-body decays B→π+π−K, we recently derived amplitudes based on two-body QCD factorization followed by π+π− final state interactions in isoscalar S- and isovector P -waves. We study here the sensitivity of the results to the values of the B to f0(980) transition form factor and to the effective decay constant of the f0(980).