Promp photon yield and υ2 coefficent from gluon fusion induced by magnetic field in heavy-ion collisions

Jorge David Castaño-Yepes,Alejandro Ayala,L A Hernández,María Elena Tejeda-Yeomans,Saúl Hernández-Ortíz,C A Dominguez

doi:10.1051/epjconf/201817208004

Abstract

We compute the production of prompt photons and the υ2 harmonic coefficient in relativistic heavy-ion collisions induced by gluon fusion in the presence of an intense magnetic field, during the early stages of the reaction. The calculations take into account several parameters which are relevant to the description of the experimental transverse momentum distribution, and elliptic flow for RHIC and LHC energies. The main imput is the strenght of the magnetic field which varies in magnitude from 1 to 3 times the pion mass squared, and allows the gluon fusion that otherwise is forbidden in the absence of the field. The high gluon occupation number and the value of the saturation scale also play an important role in our calculation, as well as a flow velocity and geometrical factors. Our results support the idea that the origin of at least some of the photon excess observed in heavy-ion experiments may arise from magnetic field induced processes, and gives a good description of the experimental data.

Highlights

It is well established that in heavy-ion experiments carried out at the CERN Large Hadron Collider and at the BNL Relativistic Heavy-Ion Col-Preprint submitted to Web of Conferences Journal lider, magnetic fields with intensities of several times the pion mass squared are produced, both in central and peripheral collisions [1, 2]
The presence of a magnetic fields in a medium with high gluon occupation number [3] allows processes in which the photon production by gluon fusion can be achieved [4, 5]. This photon production mechanism together with the common sources calculated for syncroton radiation, bremsstrahlung, pair annihilation [6, 7] and modeled by hydrodynamical and transport calculations [8, 9, 10] could explain the experimentally measured photon excess at low momentum in the invariant momentum distribution [11, 12, 13]
In this work we compute the photon production and v2 harmonic coefficient from the fusion of low momentum gluons in the presence of a magnetic field

Summary

Introduction

It is well established that in heavy-ion experiments carried out at the CERN Large Hadron Collider and at the BNL Relativistic Heavy-Ion Col-Preprint submitted to Web of Conferences Journal lider, magnetic fields with intensities of several times the pion mass squared are produced, both in central and peripheral collisions [1, 2]. Preprint submitted to Web of Conferences Journal lider, magnetic fields with intensities of several times the pion mass squared are produced, both in central and peripheral collisions [1, 2]. Studies on the centrality-dependence of these short-lived magnetic fields, show that their intensity along the reaction plane is small compared with the intensity along the normal to the reaction plane.

Results

Conclusion