Varying the chiral magnetic effect relative to flow in a single nucleus-nucleus collision**Supported by National Natural Science Foundation of China (11647306, 11747312, U1732138, 11505056, 11605054, 11628508) and US Department of Energy (DE-SC0012910)

Abstract

We propose a novel method to search for the chiral magnetic effect (cme) in heavy ion collisions. We argue that the relative strength of the magnetic field (mainly from spectator protons and responsible for the cme) with respect to the reaction plane and the participant plane is opposite to that of the elliptic flow background arising from the fluctuating participant geometry. This opposite behavior in a single collision system, hence with small systematic uncertainties, can be exploited to extract the possible cme signal from the flow background. The method is applied to existing data from rhic, and the outcome discussed.