Model-Independent Analysis of g_\mu-2

Abstract

Assuming that the scale of new physics exceeds the weak scale, we have considered all possible origins of deviations from the Standard Model in $\gmu2$. If the underlying theory can be treated perturbatively, then to account for an effect as large as has been recently reported\cite{BNL}, the only possibilities would be models that contain particles that yield direct contributions, of which SUSY models are prototypical, or models having unexpectedly light leptoquarks or having a rather exotic heavy vector boson that couples predominantly to muons. Other possibilities either are already excluded by existing experimental results or would have to be unnaturally large. If, on the contrary, the underlying new physics involves strong interactions, as in technicolor models, then the discrepancy could be accounted for by a variety of effective operators.