Centrality dependence of photon yield and elliptic flow from gluon fusion and splitting induced by magnetic fields in relativistic heavy-ion collisions

Abstract

We compute the photon yield and elliptic flow coefficient in relativistic heavy-ion collisions from gluon fusion and splitting processes induced by a magnetic field for different centralities. The calculation accounts for the intense magnetic field and the high gluon occupation number at early times. The photon production induced by these process represents an excess contribution over calculations without magnetic field effects. We compare this excess to the difference between PHENIX data and recent hydrodynamic calculations for the photon transverse momentum distribution and elliptic flow coefficient $v_2$. The time evolution of the field strength and reaction volume is computed using UrQMD. We show that with reasonable values for the saturation scale, the calculation helps to better describe the experimental results obtained at RHIC energies for the lowest part of the transverse photon momentum at different centralities.

Expanded discussion. Version to appear in The European Physical Journal A

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• Direct Photons in Hydrodynamic Modeling of Relativistic Nuclear Collisions
• Photons production in heavy-ion collisions as a signal of deconfinement phase
• Strongly interacting matter in extreme magnetic fields
• Influence of magnetic field-induced anisotropic gluon pressure during pre-equilibrium in heavy-ion collisions: A faster road towards isotropization
• Two-gluon one-photon vertex in a magnetic field and its explicit one-loop approximation in the intermediate field strength regime
• Interaction field strength between a scalar particle and two massless vector bosons in presence of an external magnetic field
• Hydrodynamic model of heavy-ion collisions with low momentum components