The measurement of the pion-nucleon scattering lengths constitutes a
high-precision test of the methods of Chiral Pertubation Theory, which is the
low-energy approach of QCD. The pion-nucleon s-wave scattering lengths are
related to the strong-interaction shift and width of the s-states of the pionic
hydrogen atom. Shift and width are determined from the measured energies and
line widths of X-ray transitions to the 1s ground state when compared to the
calculated electromagnetic values. A new experiment, set up at the
Paul-Scherrer-Institut, has completed a first series of measurements.Comment: 4 pages, 2figures, conference Moriond XXXVIII, 2003(QCD and Hadronic
Interactions