The Froissart–Stora equation describes the change in polarization which a high energy charged particle beam in a storage ring will undergoas it passes through a resonance in the spin tune. It is named after the French physicists Marcel Froissart and Raymond Stora.The polarization following passage through the resonance is given by where is the resonance strength and is the speed at which the resonance is crossed. is the initial polarization before resonance crossing. The Froissart–Stora equation has a direct analogy in condensed matter physics in the Landau-Zener effect.