Electric fields and chiral magnetic effect in Cu + Au collisions

The non-central Cu+Au collisions can create strong out-of-plane magnetic fields and in-plane electric fields. By using the HIJING model, we study the general properties of the electromagnetic fields in Cu+Au collisions at 200GeV and their impacts on the charge-dependent two-particle correlator γq1q2=〈cos⁡(ϕ1+ϕ2−2ψRP)〉 (see main text for definition) which was used for the detection of the chiral magnetic effect (CME). Compared with Au+Au collisions, we find that the in-plane electric fields in Cu+Au collisions can strongly suppress the two-particle correlator or even reverse its sign if the lifetime of the electric fields is long. Combining with the expectation that if γq1q2 is induced by elliptic-flow driven effects we would not see such strong suppression or reversion, our results suggest to use Cu+Au collisions to test CME and understand the mechanisms that underlie γq1q2.