Elastic $\pi \pi$ scattering to two loops

Abstract

We evaluate analytically the elastic $\pi \pi$ scattering amplitude to two loops in chiral perturbation theory and give numerical values for the two $S$--wave scattering lengths and for the phase shift difference ${\delta }_0^0-{\delta }_1^1$.

Comments: 10 pages, LaTeX, uses epsfig.sty, one postscript picture included. Full postscript file available at http/www.nordita.dk/locinfo/preprints/95077.ps.gz