  Axial charge in a QCD plasma is P- and CP-odd. We propose and study P- and
CP-odd observables in photon and di-lepton emissions from an axially charged
QCD plasma, which may provide possible experimental evidences of axial charge
fluctuation and triangle anomaly in the plasma created in heavy-ion collisions.
Our observables measure spin alignments of the emitted photons and di-leptons,
and are shown to be related to the imaginary part of chiral magnetic
conductivity at finite frequency-momentum, which ultimately arises from the
underlying triangle anomaly of the QCD plasma with a finite axial charge
density. We present an exemplar computation of these observables in strongly
coupled regime using AdS/CFT correspondence.
