We predict the $\eta /{\pi }^0$ ratio at low $p_T$ ($p_T\lesssim 3\mathrm{GeV}/c$) using the measured charged $K/\pi$ ratio and model input from a blast-wave framework with feed-down contributions. This approach can provide improved, data-constrained background estimates for direct-photon and dilepton measurements in heavy-ion collisions. In this approach, the explicit modeling of radial flow and hadronic feed down enables an uncertainty estimate for the low-$p_T$ extrapolation of the $\eta /{\pi }^0$ ratio. Using central Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV as an example, we find that the $\eta$-related decay-photon uncertainty at $p_T\approx 1\mathrm{GeV}/c$ is of order 10% of the expected direct-photon signal.

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• Particle & resonance production
• Photon, lepton & quark production
• Relativistic heavy-ion collisions