Photon decay in strong magnetic field in heavy-ion collisions

TL;DR

This paper calculates photon pair production in strong magnetic fields during heavy-ion collisions, revealing significant yield depletion and azimuthal asymmetry, which can help probe early magnetic fields in such collisions.

Contribution

It provides the first quantitative estimates of photon decay effects and azimuthal asymmetry due to magnetic fields in heavy-ion collisions.

Findings

Photon yield decreases by a few percent at RHIC and up to 20% at LHC.

Azimuthal asymmetry (v_2) of photons is estimated at 2% for RHIC and 14% for LHC.

Photon decay can serve as a probe for magnetic fields in early collision stages.

Abstract

We calculate the photon pair production rate in 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 v_2~2% at RHIC and v_2~14% at LHC. Photon decay measurements is an important tool for studying the magnetic fields in early stages of heavy-ion collisions.