Azimuthal flow of decay photons in relativistic nuclear collisions

Abstract

An overwhelming fraction of photons from relativistic heavy ion collisions has its origin in the decay of ${\pi }^0$ and $\eta$ mesons. We calculate the azimuthal asymmetry of the decay photons for several azimuthally asymmetric pion distributions. We find that the $k_T$ dependence of the elliptic flow parameter$v_2$ for the decay photons closely follows the elliptic flow parameter $v_2^{{\pi }^0}$ evaluated at $p_T\approx k_T+\delta$, where $\delta \approx$ 0.1 -- 0.2 GeV, for typical pion distributions measured in nucleus-nucleus collisions at relativistic energies. Similar results are obtained for photons from the 2-$\gamma$ decay of $\eta$ mesons. Assuming that the flow of ${\pi }^0$ is similar to those for ${\pi }^{+}$ and ${\pi }^{-}$ for which independent measurements would be generally available, this ansatz can help in identifying additional sources for photons. Taken along with quark number scaling suggested by the recombination model, it may help to estimate $v_2$ of the parton distributions in terms of azimuthal asymmetry of the decay photons at large $k_T$.

arXiv comment6 pages, figures added, references added, with more elaborate discussions

References in corpus (20)

• Radial and elliptic flow at RHIC: further predictions
• Hadronization in heavy ion collisions: Recombination and fragmentation of partons
• Elliptic Flow of Identified Hadrons in Au+Au Collisions at sqrt(s_NN) = 200 GeV
• Parton coalescence and antiproton/pion anomaly at RHIC
• The Effect of Shear Viscosity on Spectra, Elliptic Flow, and HBT Radii
• Hadron production in heavy ion collisions: Fragmentation and recombination from a dense parton phase
• Elliptic flow at large transverse momenta from quark coalescence
• Identified Particle Elliptic Flow in Au+Au Collisions at $\sqrt{s_{{}_{NN}}}=130$ GeV}
• Elliptic flow and incomplete equilibration at RHIC
• Common Suppression Pattern of eta and pi^0 Mesons at High Transverse Momentum in Au+Au Collisions at sqrt(s_NN) = 200 GeV
• Azimuthal anisotropy and correlations in the hard scattering regime at RHIC
• Elliptic flow of thermal photons in relativistic nuclear collisions
• Azimuthal anisotropy of K0s and Lambda prduction at mid-rapidity from Au+Au collisions at root s = 130 GeV
• Elliptic flow of multi-strange particles: fragmentation, recombination and hydrodynamics
• Measurement of identified pi^0 and inclusive photon v_2 and implication to the direct photon production in sqrt(s_NN) = 200 GeV Au+Au collisions
• Identified charged particle azimuthal anisotropy in PHENIX at RHIC
• Photon and neutral pion production in Au+Au collisions at sqrt(s_{NN}) = 130 GeV
• Azimuthal Anisotropy of Photon and Charged Particle Emission in Pb+Pb Collisions at 158 A GeV/c
• Determination of Azimuthal Anisotropy of Neutral Pions from the Measured Anisotropy of Photons in Ultra-relativistic Nuclear Collisions
• Elliptic flow from partially thermalized heavy-ion collisions

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