The heterotic string yields natural supersymmetry
  The most promising MSSM candidates of the heterotic string reveal some distinctive properties. These include gauge-top unification, a specific solution to the mu-problem and mirage pattern for the gaugino masses. The location of the top- and the Higgs-multiplets in extra dimensions differs significantly from that of the other quarks and leptons leading to a characteristic signature of suppressed soft breaking terms, reminiscent of a scheme known as natural supersymmetry. 
Sven Krippendorf, Hans Peter Nilles, Michael Ratz, Martin Wolfgang   Winkler
hep-ph hep-th