R-parity breaking via type II seesaw, decaying gravitino dark matter and PAMELA positron excess

We propose a new class of R-parity violating extension of MSSM with type 11 seesaw mechanism for neutrino masses where an unstable gravitino is the dark matter of the Universe. It decays predominantly into three leptons final states, thereby providing a natural explanation of the positron excess but no antiproton excess in the PAMELA experiment. The model can explain neutrino masses without invoking any high scale physics while keeping the pre-existing baryon asymmetry of the universe in tact. (C) 2009 Elsevier B.V. All rights reserved.