  Topological gluon configurations in quantum chromodynamics induce quark
chirality imbalance in local domains, which can result in the chiral magnetic
effect (CME)--an electric charge separation along a strong magnetic field.
Experimental searches for the CME in relativistic heavy ion collisions via the
charge-dependent azimuthal correlator ($\Delta\gamma$) suffer from large
backgrounds arising from particle correlations (e.g. due to resonance decays)
coupled with the elliptic anisotropy. We propose differential measurements of
the $\Delta\gamma$ as a function of the pair invariant mass ($m_{\rm inv}$), by
restricting to high $m_{\rm inv}$ thus relatively background free, and by
studying the $m_{\rm inv}$ dependence to separate the possible CME signal from
backgrounds. We demonstrate by model studies the feasibility and effectiveness
of such measurements for the CME search.
