SPI observations of positron annihilation radiation from the 4th   galactic quadrant: sky distribution
  During its first year in orbit the INTEGRAL observatory performed deep exposures of the Galactic Center region and scanning observations of the Galactic plane. We report on the status of our analysis of the positron annihilation radiation from the 4th Galactic quadrant with the spectrometer SPI, focusing on the sky distribution of the 511 keV line emission. The analysis methods are described; current constraints and limits on the Galactic bulge emission and the bulge-to-disk ratio are presented. 
G. Weidenspointner, V. Lonjou, J. Knoedlseder, P. Jean, M. Allain, P.   von Ballmoos, M.J. Harris, G.K. Skinner, G. Vedrenne...