Wednesday, March 16, 2011

The Desert (in Particle Physics)

This is not the kind of Desert we're talking about.

In particle physics, the desert refers to a theorized gap in energy scales between the TeV scale and the GUT scale in which no new physics appears. The idea of the desert was motivated by the observation of approximate, order of magnitude, gauge coupling unification at the GUT scale. Adding additional new physics at an intermediate scale generically disrupts the gauge coupling unification. With the Minimal Supersymmetric Standard Model particle content, adjustment of parameters can make this unification exact. This unification is not unique, since alternative scenarios like the Katoptron model can also lead to exact unification after a similar energetic desert. If neutrino masses are due to a seesaw mechanism, the seesaw scale should lie within the desert.

The attraction of a desert is that, in such a scenario, measurements of TeV scale physics at the near-future colliders LHC and ILC will allow extrapolation all the way up to the GUT scale. An alternative to a desert is a series of new physical theories unfolding with every few orders of magnitude increase in energy scale.

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