Effective Lagrangian approach to precision measurements.

Abstract

We investigate the use of effective Lagrangians to describe the effects on high-precision observables of physics beyond the Standard Model. Using the anomalous magnetic moment of the muon as an example, we detail the use of effective vertices in loop calculations. It is shown that the classical equations of motion may be used to simplify the effective Lagrangian, even when quantum loops are to be considered. Estimates are then provided of the sensitivity of new experiments measuring the muon's $ g - 2$ to the scale of physics underlying the Standard Model. This requires an estimate of the strength of the effective couplings involved. The possible coupling strengths are considered, showing that the trilinear gauge vertices can only come in at tree level if they are suppressed by 1/$\Lambda\sp4$, and so effects are minimal at all but the lowest energies.