Since the existence of supersymmetry partner virtual particles seemingly solves the heirarchy problem, it follows that it must also solve the
vacuum energy problem. The vacuum energy problem is that all calculations using only non-symmetric virtual particles results in an energy that is 120 orders of magnitude too large compared to estimates of the cosmological constant derived from astronomicaL OBSERVATIONS OF DISTANT QUASARS. Opps, forgive the caps.
As above the weak scale is 16 orders of magnitude smaller the Planck scale because superpartners have the same properties as the virtual particles and the effect of the virtual particles are cancelled by the superpartner virtual particles except for spin and CP violation. Otherwise the weak scale should equal the Planck scale.
Well exactly the same cancelation should apply to the virtual particles in vacuum. If the supersymmetric cancellation were exact, the vacuum energy would equal zero. The evidence that vacuum energy is not quite zero in comparison to the 120 order of magnitude calculation suggests that the cancellation is not exact.
Now in quantum mechanics whenever the results of a measurable process is calculated, every possible quantum path must be used, ensuring that supersymmetric cancellation is exact if superpartner properties are the same as ordinary virtual particles. The Casmir force between two plates in vacuum is in a sense a measure of vacuum energy, and calculations using only non-symmetric virtual particles agree with experiment.
So one possible conclusion is that supersymmetry does not exist in nature. The only solution to the Higgs heirarchy problem is then the multiple brane models that Randal-Sundance have proposed.
Without supersymmetry, 10-d superstring theory is also incorrect. It may be that no string theory is correct, but that the so-called multiverse consists of many 3-d universes on 4-d spacetime branes. But my take is that 26-d string theory with two timelike dimensions that inflate to 4-d spacetime universes embedded in a 4-d spacetime multiverse is still a possibility. The tachyon in 26-d theory then would explain the nearly instantaneous collapse of wavefunctions that exist in the bulk just of the brane of each 4-d universe.