0520026

We propose to continue and complete our program for observing the sky at intermediate Galactic latitudes above and below the Galactic bulge with the goal of establishing with INTEGRAL for the first time the large-scale spatial distribution of positron annihilation radiation and its spectral charateristics. This is crucial for identifying the origin(s) of the copious positrons in our Galaxy and for understanding their diffusion in the interstellar medium.We have published the first sky maps in the 511~keV line citep{Knoedlseder05} and in the positronium continuum citep{Weidenspointner_etal_06} which clearly showed that the positron annihilation radiation from our Galaxy is brightest around the Galactic center. Subsequent work showed that all but two scenarios remain for the Galactic distribution of positron annihilation radiation: ``bulge + thick disk or ``halo + thin disk citep{Weidenspointner07}. We propose to break the current degeneracy between viable scenarios byobserving at intermediate latitudes south of the Galactic bulge ($l = pm 20^circ$ $b=-20^circ$) for a total of 2~Ms. These observations will help to deepen and homogenize the exposure around the Galactic bulge a prerequisit for obtaining the best possible results on the intriguing annihilation emission observed from intermediate latitudes in the inner Galaxy. [truncated! Please see actual data for full text]