Probing the quark condensate by means of pi-pi scattering

Abstract

The available experimental information is consistent with the Weinberg predictions for the threshold parameters of pi-pi-scattering. The data, however, only test those relations that are insensitive to the quark masses m_u and m_d. Recent theoretical progress leads to remarkably sharp predictions for the behaviour of the S- and P-wave phase shifts in the elastic region -- one of the very few low energy phenomena in QCD, where theory is ahead of experiment and where new precision data would subject the theory to a crucial test (Talk given at the DAFCE workshop, Frascati, November 1996).