Constraining the Low-p_T η/π^0 Ratio for Direct-Photon Analyses with Blast-Wave Fits to π, K, and p Spectra

Abstract:

We predict the η/π0 ratio at low pT (pT≲3 GeV/c) using the measured charged K/π ratio and model input from a blast-wave framework with feeddown 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 feeddown enables an uncertainty estimate for the low-pT extrapolation of the η/π0 ratio. Using central Pb-Pb collisions at sNN−−−−√=2.76 TeV as an example, we find that the η-related decay-photon uncertainty at pT≈1 GeV/c is of order 10\% of the expected direct-photon signal.

K. Reygers, A. Kirchner, A. Mazeliauskas, „Constraining the Low-pT η/π0 Ratio for Direct-
Photon Analyses with Blast-Wave Fits to π, K, and p Spectra“, 10. Juni 2026, arXiv:2606.12619 (2026).

https://arxiv.org/abs/2606.12619

Related to Project A01