Natural Dark Matter from Type I String Theory

We study neutralino dark matter within a semi-realistic type I string model, where supersymmetry breaking arises from F-terms of moduli fields parameterised in terms of Goldstino angles, which automatically gives rise to non-universal soft third sfamily and gaugino masses. We study the fine-tuning sensitivities for dark matter and electroweak symmetry breaking across the parameter space of the type I string model, and compare the results to a similar analysis in the non-universal MSSM. Within the type I string model we find that neutralino dark matter can be naturally implemented in the $\stau$ bulk region, the $Z^0$ resonance region and the maximally tempered Bino/Wino/Higgsino region, in agreement with the results of the non-universal MSSM analysis. We also find that in the type I string model the ``well-tempered'' Bino/Wino region is less fine-tuned than in the MSSM, whereas the $\stau$ co-annihilation region exhibits a significantly higher degree of fine-tuning than in the MSSM.