The interactions of π⁻-mesons with complex nuclei in the energy range (100–800) MeV. III. The interaction lengths and elastic scattering of 300 MeV π⁻-mesons in G5 emulsion

Abstract

Abstract A stack of pellicles has been exposed to the 300 MeV πminus;-meson beam of the 660 MeV proton synchrotron at C.E.R.N., Geneva. The interaction lengths for the production of inelastic interactions and elastic scatterings through projected angles greater than 5°, found by scanning along 140 m of track, are (37.9 ± 2.0) cm and (77.4 ± 5.8) cm respectively compared to the geometrical interaction length of 29.3 cm. By comparison with the optical model the absorption coefficient and change in wave number are (1.53 ± 0.15) 1012 cm−1 and ± (1.35 ± 0.12)1012 cm−1, corresponding to a nuclear potential with a real component of (25 ± 1) MeV (of which the sign is not known), an imaginary component, −(14.1 ± 1.4) MeV and a mean free path for interaction in nuclear matter of (6.5 ± 0.7) 10−13 cm. The differences from the expected values are consistent with a considerable reduction within the nucleus of the cross section for elastic scattering of π-mesons by nucleons.