FINAL RESULTS OF A MEASUREMENT OF ann FROM THE REACTION π−d → 2nγ

Abstract

Publisher Summary This chapter discusses the measurement of the neutron–neutron S-wave scattering length in the determination of the exact role of direct and indirect electromagnetic effects in breaking strong interaction symmetries. As free neutron–neutron scattering events are not available in useful quantities, the knowledge of ann comes from final-state interactions that involves two and more nucleons. The chapter discusses an experiment performed at the LBL 184” synchrocyclotron in which all three final-state particles were detected and the energy of the neutrons were measured by time-of-flight techniques. This allowed a three-constraint fit to the hypothesis of π–d → 2nγ with a reconstructed photon energy resolution of better than 50 MeV or 0.05%. The experiment was performed with negative pions captured at rest by deuterons; therefore, the lab and c–m system were the same, and there were two independent variables neglecting the orientation of and rotations in the 2nγ plane. In the result of the experiment, an average of the two Monte Carlo hypotheses was chosen.