The charge asymmetry (A(ch)) dependence of the pi(-) and pi(+) elliptic flow difference, Delta v(2) (A(ch)), has been regarded as a sensitive observable for the possible chiral magnetic wave (CMW) in relativistic heavy ion collisions. In this work, we first demonstrate that, due to nonflow backgrounds, the flow measurements by the Q-cumulant method using all charged particles as reference introduce a trivial linear term to Delta v(2) (A(ch)). The trivial contribution to the slope of triangle flow difference Delta v(2) (A(ch)) can be negative if the nonflow is dominated by back-to-back pairs. After eliminating the trivial term, we find that the nonflow between like-sign pairs gives rise to an additional positive slope to Delta v(2) (A(ch)) because of the larger multiplicity dilution to pi(+) (pi(-)) at positive (negative) A(ch). We further find that the competition between different pi sources can introduce another nontrivial linear-A(ch) term due to their different multiplicity fluctuations and anisotropic flows. We then study the effect of neutral cluster (resonance) decays as a mechanism for local charge conservation on the slope parameter of Delta v(2) (A(ch)). We find that the slope parameter is sensitive to the kinematics of those neutral clusters. Light resonances give positive slopes while heavy resonances give negative slopes. Local charge conservation from continuum cluster mass distribution can give a positive slope parameter comparable to experimental data. Our studies indicate that many non-CMW physics mechanisms can give rise to a A(ch)-dependent Delta v(2) (A(ch)) and the interpretation of Delta v(2) (A(ch)) in terms of the CMW is delicate.
展开▼
