Separation of flow from the chiral magnetic effect in U+U collisions using spectator asymmetry

We demonstrate that the prolate shape of the uranium nucleus generates anticorrelation between spectator asymmetry and initial-state ellipticity of the collision zone, providing a way to constrain the initial event shape in U $+$ U collisions. As an application, we show that this can be used to separate the background contribution due to flow from the signals of the chiral magnetic effect.