Muon g−2, dark matter detection and accelerator physics

Abstract

We examine the recently observed deviation of the muon g−2 from the Standard Model prediction within the framework of gravity mediated SUGRA models with R-parity invariance. Universal soft breaking (mSUGRA) models, and models with nonuniversal Higgs and third generation squark/slepton masses at M G are considered. All relic density constraints from stau–neutralino co-annihilation and large tan β NLO corrections for b→ sγ decay are included, and we consider two possibilities for the light Higgs: m h >114 GeV and m h >120 GeV. The combined m h , b→ sγ and a μ bounds give rise to lower bounds on tan β and m 1/2, while the lower bound on a μ gives rise to an upper bounds on m 1/2. These bounds are sensitive to A 0, e.g., for m h >114 GeV, the 95% C.L. is tan β>7(5) for A 0=0(−4 m 1/2), and for m h >120 GeV, tan β>15(10). The positive sign of the a μ deviation implies μ>0, eliminating the extreme cancellations in the dark matter neutralino–proton detection cross section so that almost all the SUSY parameter space should be accessible to future planned detectors. Most of the allowed parts of parameter space occur in the co-annihilation region where m 0 is strongly correlated with m 1/2. The lower bound on a μ then greatly reduces the allowed parameter space. Thus using 90% C.L. bounds on a μ we find for A 0=0 that tan β⩾10 and for tan β⩽40 that m 1/2=(290–550) GeV and m 0=(70–300) GeV. Then the tri-lepton signal and other SUSY signals would be beyond the Tevatron Run II (except for the light Higgs), only the τ ̃ 1 and h and (and for part of the parameter space) the e ̃ 1 will be accessible to a 500 GeV NLC, while the LHC would be able to see the full SUSY mass spectrum.