Its surprising to see PAMELA data explanation within the framework of NMSSM...

After PAMELA (A Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) data have come out its very common to find at least one paper on arXiv which carries an explanation for the observed positron excess observed by PAMELA. These positrons carry much more energy than usual ones coming from pulsars or other astrophysical sources. Thus the most promising explanation for their source is cold dark matter annihilation in the galactic halo. This however became a problem for particle physicists to explain in the context of most popular dark matter models like supersymmetric extension of standard model. In these models generally the Lightest Super-particle (LSP) protected by R-parity is the most favourite dark matter candidate. The trouble was that the LSP is generally the neutralino (combination of neutral gauginos and higgsinos) which is a majorana fermion and hence its annihilation to fermions will be helicity suppressed. Thus we expect dominance of heavier quarks as the final product after their annihilation rather than positrons as observed by PAMELA. That's why people started talking about various new models containing some hidden sector, dark force etc with a light gauge boson (~GeV) whose decay to heavy quarks is kinematically not favoured. I wont go on talking about them now. The standard reference is the paper by Arkani-Hmaed et al.(http://arxiv.org/abs/0810.0713).
Today morning I was however surprised to see a paper by Bai, Carena and Lykken (Fermilab) (http://arxiv.org/abs/0905.2964) where they have come out with an explanation of PAMELA data within the NMSSM(Next to MSSM) framework. This looks more natural to me than those papers which talk about dark forces , hidden sectors etc. If we have an explanation within our own sector there is no point in bringing more complications by talking about one more force. In this paper they have proposed that the neutralinos(which is the LSP) annihilate most dominantly to the lightest CP-even scalar h_1 plus the lightest CP-odd scalar a_1. The annihilation takes place via resonance CP-odd scalar a_2. For LSP mass less than top quark mass a_2 will dominantly go to a_1 and h_1 and a_1 being light (~GeV) will go to \tau^+ \tau^- or \mu^+ \mu^- depending on its exact mass. Their parameter space is also in agreement with the null searches for light bosons like a_1. This paper is damn long. So far I am pretty convinced with their arguments and results. The good thing for me was the idea of resonance production. This is the first time I have seen this idea being implemented like this. If I get enough resources and time(and help from advisor as well as colleagues), will definitely try to use it in the context of other models as well.