before 1 PeV, leading to other new physics in the TeVs. The observed Higgs boson decay modes and rates are so far consistent with the Standard Model. Counter evidence So far there is no direct evidence of new fundamental particles with masses between the electroweak and GUT scale, consistent with the desert. However, there are some theories about why such particles might exist: The leading theoretical explanations of neutrino masses, the various seesaw models, all require new heavy neutrino states below the GUT scale. Both weakly interacting massive particles (WIMP) and axion models for dark matter require the new, long-lived particles to have masses far below the GUT scale. In the Standard Model, there is no physics which stabilizes the Higgs boson mass to its actual observed value. Since the actual value is far below the GUT scale, whatever new physics ultimately does stabilize it must become apparent at lower energies too. Precision measurements have produced several outstanding discrepancies with the Standard Model in recent years. These include anomalies in certain B meson decays and a discrepancy in the measured value of the Muon g-2 (anomalous magnetic moment). Depending on the results of currently ongoing experiments, these effects may already indicate the existence of unknown new particles below about 100 TeV. References External links Grand Unified Theory Physics beyond the Standard Model