194 research outputs found

    Elliptic flow of thermal photons and formation time of quark gluon plasma at RHIC

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    We calculate the elliptic flow of thermal photons from Au+Au collisions at RHIC energies for a range of values for the formation time τ0\tau_0 but fixed entropy (or particle rapidity density). The results are found to be quite sensitive to τ0\tau_0. The v2v_2 for photons decreases as τ0\tau_0 decreases and admits a larger contribution from the QGP phase which has a smaller v2v_2. The elliptic flow coefficient for hadrons, on the other hand, is only marginally dependent on τ0\tau_0.Comment: 2 extra figures and discussion added. To appear in Physical Review C (Rapid Communication

    Azimuthal flow of decay photons in relativistic nuclear collisions

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    An overwhelming fraction of photons from relativistic heavy ion collisions has its origin in the decay of π0\pi^0 and η\eta mesons. We calculate the azimuthal asymmetry of the decay photons for several azimuthally asymmetric pion distributions. We find that the kTk_T dependence of the elliptic flow parameterv2v_2 for the decay photons closely follows the elliptic flow parameter v2π0v_2^{\pi^0} evaluated at pTkT+δp_T \approx k_T+\delta, where δ\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-γ\gamma decay of η\eta mesons. Assuming that the flow of π0\pi^0 is similar to those for π+\pi^+ and π\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 v2v_2 of the parton distributions in terms of azimuthal asymmetry of the decay photons at large kTk_T.Comment: 6 pages, figures added, references added, with more elaborate discussion