Photon decay in a strong magnetic field in heavy-ion collisions

We calculate the photon pair production rate in a strong magnetic field created in off-central heavy-ion collisions. Photon decay leads to depletion of the photon yield by a few percent at RHIC and by as much as 20% at the LHC. It also generates a substantial azimuthal asymmetry (elliptic flow) of the final photon distribution. We estimate upsilon(2) approximate to 2% at RHIC and upsilon(2) approximate to 14% at LHC. Photon decay measurements is an important tool for studying the magnetic fields in early stages of heavy-ion collisions.