  It has been suggested that local parity violation in QCD would lead to charge
separation of quarks by the Chiral Magnetic Effect (CME) in heavy ion
collisions. Charge separation could yield a dynamical charge multiplicity
asymmetry with respect to the reaction plane. In this talk, we report results
on charge multiplicity asymmetry correlations in $\sqrt{s_{NN}}$ = 200 GeV
Au+Au and d+Au collisions by the STAR experiment, as well as from the RHIC beam
energy scan. We found that the correlation results could not be explained by
CME alone. To gain further insights, we study our results as a function of the
measured azimuthal angle range as well as the event-by-event anisotropy
parameter $v_2$. The results indicate that the charge separation effect appears
to be in-plane rather than out-of-plane. We found that the charge separation
effect is proportional to the event-by-event $v_2$ and consistent with zero in
events with $v_2 \approx 0$. Our studies suggest that the charge separation
effect, within the statistical error, may be a net effect of event anisotropy
and correlated particle production. Possible upper limit on the CME imposed by
our data will be discussed.
