Probing supergravity grand unification in the Brookhaven g-2 experiment

A quantitative analysis of ${\mathit{a}}_{\mathrm{\mu }}$≡1/2(g-2${)}_{\mathrm{\mu }}$ within the framework of supergravity grand unification and radiative breaking of the electroweak symmetry is given. It is found that ${\mathit{a}}_{\mathrm{\mu }}^{\mathrm{SUSY}}$ is dominated by the chiral interference term from the light chargino exchange, and that this term carries a signature which correlates strongly with the sign of μ. Thus as a rule ${\mathit{a}}_{\mathrm{\mu }}^{\mathrm{SUSY}}$>0 for μ>0 and ${\mathit{a}}_{\mathrm{\mu }}^{\mathrm{SUSY}}$<0 for μ<0 with very few exceptions when tanβ∼1. At the quantitative level it is shown that if the E821 BNL experiment can reach the expected sensitivity of 4×${10}^{\mathrm{-}10}$ and there is a reduction in the hadronic error by a factor of 4 or more, then the experiment will explore a majority of the parameter space in the ${\mathit{m}}_0$-${\mathit{m}}_{\mathit{g}\mathrm{̃}}$ plane in the region ${\mathit{m}}_0$≲400 GeV, ${\mathit{m}}_{\mathit{g}\mathrm{̃}}$≲700 GeV for tanβ≳10 assuming the experiment will not discard the standard model result within its 2σ uncertainty limit. For smaller tanβ, the SUSY reach of E821 will still be considerable. Further, if no effect within the 2σ limit of the standard model value is seen, then large tanβ scenarios will be severely constrained within the current naturalness criterion, i.e., ${\mathit{m}}_0$,${\mathit{m}}_{\mathit{g}\mathrm{̃}}$≲1 TeV. © 1996 The American Physical Society.