Dark Matter in Supergravity

Abstract

We consider neutralino-proton cross sections for halo dark matter neutralinos $\left( {\tilde{\chi }_{1}^{0}} \right)$ within the framework of supergravity models with R-parity invariance for models with universal soft breaking (mSUGRA) and models with nonuniversal soft breaking. The analysis includes the necessary corrections to treat the large tanβ region (i.e. L-R mixing in the squark and slepton mass matrices, loop corrections to the b and τ masses,etc) and includes all coannihilation phenomena. For mSUGRA, dark matter detectors with current sensitivity are seen to be probing the region where tanβ ≳25, ${{\Omega }_{{\tilde{\chi }_{1}^{0}}}}{{h}^{2}} < 0.1,{{m}_{{\tilde{\chi }_{1}^{0}}}} \lesssim 90GeV$, and for the light Higgs, m _h ≲ 120 GeV. Nonuniversal models can have a much larger cross section, and current detectors can probe part of the parameter space where tanß ≳ 4. Minimum cross sections are generally greater than 10^–9 pb to 10^–10 pb for m _1/2 = 600 GeV, (and hence accessible to planned future detectors), with the exception of a region when µ < 0 where for m _1/2 ≳ 450 GeV, 4 ≲ tanβ ≲ 20, the cross section drops to a minimum of about 1 × 10^–12 pb at m _1/2 = 600 GeV, tanβ ⋍ 10. In this region, the gluino and squarks lie above 1 TeV, but should still be accessible to the LHC.