  Over almost all of minimal supergravity (mSUGRA or CMSSM) model parameter
space, there is a large overabundance of neutralino cold dark matter (CDM). We
find that the allowed regions of mSUGRA parameter space which match the
measured abundance of CDM in the universe are highly fine-tuned. If instead we
invoke the Peccei-Quinn-Weinberg-Wilczek solution to the strong CP problem,
then the SUSY CDM may consist of an axion/axino admixture with an axino mass of
order the MeV scale, and where mixed axion/axino or mainly axion CDM seems
preferred. In this case, fine-tuning of the relic density is typically much
lower, showing that axion/axino CDM (a\tilde{a}CDM) is to be preferred in the
paradigm model for SUSY phenomenology. For mSUGRA with a\tilde{a}CDM, quite
different regions of parameter space are now DM-favored as compared to the case
of neutralino DM. Thus, rather different SUSY signatures are expected at the
LHC in the case of mSUGRA with a\tilde{a}CDM, as compared to mSUGRA with
neutralino CDM.
