On the role of magnetic field in photon excess in heavy ion collisions

TL;DR

This paper investigates how magnetic fields influence the excess of photons observed in heavy-ion collisions, attributing a significant part of the excess to synchrotron radiation and analyzing its anisotropic properties.

Contribution

It provides a detailed calculation of synchrotron photon spectra considering realistic magnetic field structures in heavy-ion collisions, highlighting their role in photon excess.

Findings

Synchrotron radiation accounts for a significant photon excess at 1-3 GeV.

The azimuthal anisotropy coefficients are v2=4/7 and v4=1/10, independent of photon momentum and centrality.

Magnetic field effects are crucial in understanding photon production in heavy-ion collisions.

Abstract

Synchrotron photon spectrum in heavy-ion collisions is computed taking into account the spatial and temporal structure of magnetic field. It is found that a significant fraction of photon excess in heavy-ion collisions in the region $k_\bot=1-3$GeV can be attributed to the synchrotron radiation. Azimuthal anisotropy of the synchrotron photon spectrum is characterized by the Fourier coefficients $v_2=4/7$ and $v_4=1/10$ that are independent of photon momentum and centrality.