On the evaluation of the real parts of forward pp amplitudes from the data at small t

Abstract

We discuss the problem of the evaluation of the real parts of forward pp amplitudes directly from the data at small t. The expressions for daldt and for a number of polarisation parameters are derived in the limit of small t by means of an expansion of the non-singular parts of the amplitudes in powers of t. The analysis of the data at small t available in the energy range 330-800 MeV is performed, and the real parts of forward mixed amplitudes are determined. A method suitable for calculation of the Bethe phases at low and medium energies is proposed, and the real parts of forward hadronic amplitudes are calculated. Comparison of these 'measured' real parts with those predicted by the forward dispersion relations reveals a rather satisfactory agreement for the real parts of all three forward hadronic amplitudes.