Pionic deuterium

The strong-interaction shift epsilon(pi D)(1s) and broadening Gamma(pi D)(1s) in pionic deuterium have been determined in a high statistics study of the pi D(3p-1s) X-ray transition using a high-resolution crystal spectrometer. The pionic deuterium shift will provide constraints for the pion-nucleon isospin scattering lengths extracted from measurements of shift and broadening in pionic hydrogen. The hadronic broadening is related to pion absorption and production at threshold. The results are epsilon(pi D)(1s) = (-2356 +/- 31) meV (repulsive) and Gamma(pi D)(1s) = (1171(-49)(+23)) meV yielding for the complex pi D scattering length apD = [-(24.99 +/- 0.33)+ i(6.22(-0.26)(+0.1)2)] x 10(-3) m(pi)(-1). From the imaginary part, the threshold parameter for pion production is obtained to be alpha = (251(-11)(+5))mu b. This allows, in addition, and by using results from pion absorption in He-3 at threshold, the determination of the effective couplings g(0) and g(1) for s-wave pion absorption on isoscalar and isovector NN pairs.