CHAPTER 5 - THE EXPERIMENTS OF BLEULER AND BRADT, WU AND SHAKNOV, OF LANGHOFF, AND OF KASDAY, ULLMANN, AND WU

Abstract

This chapter discusses the experiments in which polarization correlations are observed for pairs of photons traveling in opposite directions, where this time the source of the photon pair is an annihilating positronium atom at rest. Because no effective polarization filters are available for photons as hard as annihilation radiation, the polarization is measured indirectly through the effectiveness of Compton scattering at chosen angles. The annihilation of positronium might be described crudely as a transition of a positive-energy electron at rest into a hole in the negative-energy states at rest. The initial state of the positronium is assumedly the ground level S-state, so that the total angular momentum is j = 1 or 0 depending upon whether the spins of the positon and the negaton line up or not. The final state has all of this angular momentum, so that the odd final photon state has j = 0 if it arises from annihilation of positronium in the singlet state, and has j = 1 when it arises from annihilation of positronium in the triplet state.