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 parameterisedin terms of Goldstino angles, which automatically gives rise to non-universalsoft third sfamily and gaugino masses. We study the fine-tuning sensitivitiesfor dark matter and electroweak symmetry breaking across the parameter space ofthe type I string model, and compare the results to a similar analysis in thenon-universal MSSM. Within the type I string model we find that neutralino darkmatter can be naturally implemented in the $\stau$ bulk region, the $Z^0$resonance region and the maximally tempered Bino/Wino/Higgsino region, inagreement with the results of the non-universal MSSM analysis. We also findthat in the type I string model the ``well-tempered'' Bino/Wino region is lessfine-tuned than in the MSSM, whereas the $\stau$ co-annihilation regionexhibits a significantly higher degree of fine-tuning than in the MSSM.Comment: 22 pages, 5 figure