Photoproduction of Low-Energy Charged Pions from Deuterium

Accurate measurements have been made of the $\frac{{\pi }^{-}}{{\pi }^{+}}$ photoproduction ratio on deuterium, in the gammaray energy range 165-210 MeV, for several angles: 155°, 125°, 90° (center-of-mass system) and along Baldin's kinematical line. These last data are new contributions: $\frac{{\pi }^{-}}{{\pi }^{+}}=1.20\mathrm{}\pm 0.03$ averaged between 165 and 180 MeV. The others are improvements of the accuracy of previous data. The comparison with Ball's theory, corrected for taking into account the $I=\frac{1}{2}$ phase shifts, gives for the coupling constant $\Lambda$ for $\gamma -\pi -p$ the value: $0.25<+\frac{\Lambda }{e}<0.75\mathrm{}$.