LITTLE HIGGS GOES TO TASI

Abstract

A few years before the start of the LHC program, electroweak symmetry breaking remains poorly understood. The detailed quantitative fit of Standard Model predictions to precision experiments at the weak scale strongly suggests that electroweak symmetry is broken by one or more weakly coupled Higgs doublets. However, fundamental scalar particles suffer from a radiative instability to their masses, leading us to expect additional structure (such as compositeness, supersymmetry, little Higgs, ...) near the weak scale. Interestingly, we can turn this problem into a prediction for the LHC. The argument goes as follows: Let us assume that precision electroweak data are indeed telling us that there are no new particles beyond the Standard Model (with the exception of possible additional Higgs doublets) with masses at or below the weak scale. Then physics at the weak scale may be described by an “effective Standard Model” which has the particle content of the Standard Model and in which possible new physics is parametrized by higher dimensional operators suppressed by the new physics scale Λ > ∼ TeV. All renormalizable couplings are as in the Standard Model. If there are additional Higgs fields then more complicated Higgs self-couplings as