  A new parametrization of the multi-channel S-matrix is used to fit scattering
data and then to locate the resonances as its poles. The S-matrix is written in
terms of the corresponding "in" and "out" Jost matrices which are expanded in
the Taylor series of the collision energy E around an appropriately chosen
energy E0. In order to do this, the Jost matrices are written in a
semi-analytic form where all the factors (involving the channel momenta and
Sommerfeld parameters) responsible for their "bad behaviour" (i.e. responsible
for the multi-valuedness of the Jost matrices and for branching of the Riemann
surface of the energy) are given explicitly. The remaining unknown factors in
the Jost matrices are analytic and single-valued functions of the variable E
and are defined on a simple energy plane. The expansion is done for these
analytic functions and the expansion coefficients are used as the fitting
parameters. The method is tested on a two-channel model, using a set of
artificially generated data points with typical error bars and a typical random
noise in the positions of the points.

Nuclear Theory;Nuclear Experiment