Patterns of deviation from the standard model

Abstract Effective lagrangians can be used to parametrize the effects of physics beyond the Standard Model. Assuming the complete theory is a gauge theory, we determine which effective operators may be generated at tree level, and which are only generated at loop level. The latter are suppressed by factors of 1 16 π 2 and will therefore be quite difficult to detect. In particular, all operators changing the Standard-Model structure of the triplegauge-vector couplings fall into this category. We also point out that in certain cases, dimension-eight operators may be more important than dimension-six operators. We discuss both the linear and non-linear representation of the Higgs sector.