  Precision measurements of the anomalous magnetic moment of the muon depend on
the correct collective mode assignment of the coherent betatron oscillations in
the beam. Presently, there is a disagreement between experiment and theory for
the horizontal betatron frequency. The discrepancy is here resolved by our
computations of electrostatic beam focusing. The correct treatment of the
betatron effects renders less likely the need for non-standard model
corrections to the muon g-2.
