Karplus, R.; Ruderman, M.A.; Applications of Causality to Scattering
Phys. Rev. 98 (1955) 771;
The optical dispersion relations are extended to the scattering of massive particles and are applied to the nuclear interaction of the pion-nucleon system. The sign of the forward scattering amplitude is unambiguously inferred from measured total cross sections and found to agree with that determined from Coulomb interference.
Related references See also W. Heisenberg, Z. Phys. 120 (1943) 513;
W. Heisenberg, Z. Phys. 120 (1943) 673;
R. de L. Kronig, J. Opt. Soc. Am. 12 (1926) 547, Physica 12 (1946) 543;
H. A. Kramers, Atti. Congr. Intern. Fisici, Como. 2 (1927) 545;
N. G. van Kampen, Phys. Rev. 89 (1953) 1072;
N. G. van Kampen, Phys. Rev. 91 (1953) 1267;
M. Gell-Mann, M. L. Goldberger, and W. E. Thirring, Phys. Rev. 95 (1954) 1612;
W. Schutzer and J. Tiomno, Phys. Rev. 83 (1951) 249;
Forward dispersion relations for massive particles.