We recently started testing Chao’s proposed new matrix formalism for describing the spin dynamics due to a single spin resonance. The Chao formalism is probably the first fundamental improvement of the Froissart-Stora equation in that it allows analytic calculations of the beam polarization’s behavior inside a resonance. We tested the Chao formalism using a $1.85\mathrm{GeV}/c$ polarized deuteron beam stored in COSY, by sweeping an rf dipole’s frequency through 200 Hz, while varying the distance from the sweep’s end frequency to an rf-induced spin resonance’s central frequency. Since the Froissart-Stora equation itself can make no prediction inside a resonance, we compared our experimental data with the predictions of the Chao formalism and those of an empirical two-fluid model based on the Froissart-Stora equation. The data strongly favor the Chao formalism.

• Received 8 February 2007

DOI:https://doi.org/10.1103/PhysRevSTAB.10.041001

This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.