SUSY Dark Matter: Closing The Parameter Space

Abstract

We consider here the constraints in SUGRA models on the SUSY parameter space due to current experimental bounds on the light Higgs mass m_h, the b-> s gamma decay, the amount of neutralino cold dark matter Omega h^2, and the muon magnetic moment. Models with universal soft breaking (mSUGRA) and non-universal gaugino or Higgs masses at M_G are examined. For mSUGRA, the m_h, b->s gamma and Omega h^2 constraints imply a lower bound on the gaugino mass of m_{1/2}>~300GeV implying the gluino and squarks have mass >~700GeV, and the neutralino >~120GeV. The current status of the Brookhaven muon g - 2 experiment is reviewed, and if the Standard Model (SM) contribution evaluated using the e^+ + e^- data is correct, a 2 sigma bound on the deviation of experiment from the SM produces an upper bound on m_{1/2} that eliminates the "focus point" regions of parameter space. Dark matter (DM) detection cross sections range from 5\times10^{-8} pb to 5\times10^{-10} pb which would be accessible to future planned detectors. The SUSY decay B_s->\mu^+ +\mu^- is seen to be accessible to the Tevatron Run 2B with 15 fb^{-1} luminosity for tanbeta >~30. The most favorable signals of SUSY for linear colliders are stau pair production and neutralino pair production, though it will require an 800GeV machine to cover the full parameter space. Non-universal models can modify some of the above results. Thus a non-universal (heavier) gluino mass at M_G can significantly reduce the lower bound constraints of b\to s gamma and m_h giving rise to a lighter SUSY spectrum. A heavier up Higgs mass can open an additional region with allowed relic density arising from annihilation via the s-channel Z diagram with an O(10) larger DM detector cross section.