Probing supergravity grand unification in the Brookhaven g-2 experiment.

Abstract

A quantitative analysis of ${\mathit{a}}_{\mathrm{\ensuremath{\mu}}}$\ensuremath{\equiv}1/2(g-2${)}_{\mathrm{\ensuremath{\mu}}}$ within the framework of supergravity grand unification and radiative breaking of the electroweak symmetry is given. It is found that ${\mathit{a}}_{\mathrm{\ensuremath{\mu}}}^{\mathrm{SUSY}}$ 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 \ensuremath{\mu}. Thus as a rule ${\mathit{a}}_{\mathrm{\ensuremath{\mu}}}^{\mathrm{SUSY}}$>0 for \ensuremath{\mu}>0 and ${\mathit{a}}_{\mathrm{\ensuremath{\mu}}}^{\mathrm{SUSY}}$0 for \ensuremath{\mu}0 with very few exceptions when tan\ensuremath{\beta}\ensuremath{\sim}1. At the quantitative level it is shown that if the E821 BNL experiment can reach the expected sensitivity of 4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}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 ${\mathit{m}}_{0}$-${\mathit{m}}_{\mathit{g}\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}$ plane in the region ${\mathit{m}}_{0}$\ensuremath{\lesssim}400 GeV, ${\mathit{m}}_{\mathit{g}\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}$\ensuremath{\lesssim}700 GeV for tan\ensuremath{\beta}\ensuremath{\gtrsim}10 assuming the experiment will not discard the standard model result within its 2\ensuremath{\sigma} uncertainty limit. For smaller tan\ensuremath{\beta}, the SUSY reach of E821 will still be considerable. Further, if no effect within the 2\ensuremath{\sigma} limit of the standard model value is seen, then large tan\ensuremath{\beta} scenarios will be severely constrained within the current naturalness criterion, i.e., ${\mathit{m}}_{0}$,${\mathit{m}}_{\mathit{g}\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}$\ensuremath{\lesssim}1 TeV. \textcopyright{} 1996 The American Physical Society.