Flows and polarization of early photons with magnetic field at strong coupling

TL;DR

This paper investigates how magnetic fields influence early photon emission and polarization asymmetries in strongly coupled plasmas, revealing significant effects of the chiral anomaly at low frequencies, relevant to heavy-ion collision experiments.

Contribution

It introduces a gauge/gravity framework to compute azimuthal and polarization asymmetries of photon emission in magnetic fields, highlighting the impact of the chiral anomaly.

Findings

Azimuthal asymmetry of photon emission is significantly affected by magnetic fields.

Polarization asymmetry shows strong dependence on the triangle anomaly.

Chiral anomaly effects are prominent below 1 GeV frequency regime.

Abstract

Recent experimental results from RHIC and LHC on hard photon emission rates in heavy-ion collisions indicate a large azimuthal asymmetry of photon emission rate parameterized by the elliptic flow v_2. Motivated by a recent proposal that the early magnetic field created by two colliding heavy-ions may be responsible for this large azimuthal asymmetry of photon emission rate, we compute the azimuthal dependence of the photon emission rate from a strongly coupled finite temperature plasma with magnetic field in the framework of gauge/gravity correspondence. We also propose and compute a new observable, "in/out-plane polarization asymmetry", constructed from the polarization dependence of the photon emission rates. We observe that both the azimuthal and polarization asymmetry of photon emissions are strongly affected by the triangle anomaly (chiral anomaly) for low frequency regime below 1 GeV.