Measurement of the Spin-Flip Probability in Photoproduction of Negative Pions from Deuterium

Abstract

Negative pions photoproduced from deuterium (i.e., from the neutron) by the bremsstrahlung of the Berkeley synchrotron have been investigated by observing pion-proton coincidences. A $(\mathrm{C}{\mathrm{D}}_{2})n\ensuremath{-}(\mathrm{C}{\mathrm{H}}_{2})n$ subtraction yields the neutron contribution. The purpose of the investigation is to determine how often the initial triplet spin state of the deuteron changes to a singlet spin state for the two final identical nucleons in the reaction $\ensuremath{\gamma}+d\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}+p+p$. LeLevier has calculated the pion-energy spectra under two assumptions: (a) the spin state always remains the same, and (b) the spin state always changes. The experimental measurements are integrals over meson energy from a lower limit upwards, and over the time of flight between the proton and the pion, within the resolution time of the coincidence system. Thus, when the theoretically predicted spectra are folded into the experimental resolution of the equipment and the bremsstrahlung spectrum, there results a number proportional to the experimental measurement. The ratios of various experimental measurements can be compared with the theoretically predicted ratios. Within the limitations of the theory and the accuracy of the experimental measurements, the results indicate an interaction that is intermediate between the spin state's always changing and the spin state's never changing.