Wednesday, July 29, 2009

Positron excess in cosmic rays is not being possible to explain with existing numerial packages...:(

I was looking for numerical packages available for calculating dark matter relic density like micrOMEGA, DarkSUSY etc. It seems to me that these packages won't be useful for calculating positron fraction which can fit with the observed PAMELA, FERMI data. One main reason is that the cross section of dark matter annihilation should be very high (than allowed from the thermal dark matter relic density argument). We need a boost of the order of ~100 so as to fit the positron excess with the observed data. Thus having a particle physics model where the proposed dark matter particle annihilates only to leptons in the tree level is not enough, we also need to look for some boost factor. I don't think the existing packages include such boost factor at all. What I am thinking of doing is that calculate the relic density (approximate) from the standard formula, find out the cross section of dark matter annihilation to all possible particles at tree level and then find out the positron fraction coming from it including the boost factor. I have no idea whether this approach will be good or not but have no other option than to do it.

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