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arXiv · 2512.01638

Searching for EeV photons with Telescope Array Surface Detector and neural networks

Telescope Array Collaboration·R. U. Abbasi·T. Abu-Zayyad·M. Allen·J. W. Belz·D. R. Bergman·F. Bradfield·I. Buckland·W. Campbell·B. G. Cheon·K. Endo·A. Fedynitch·T. Fujii·K. Fujisue·K. Fujita·M. Fukushima·G. Furlich·A. Galvez Urena·Z. Gerber·N. Globus·T. Hanaoka·W. Hanlon·N. Hayashida·H. He·K. Hibino·R. Higuchi·D. Ikeda·D. Ivanov·S. Jeong·C. C. H. Jui·K. Kadota·F. Kakimoto·O. Kalashev·K. Kasahara·Y. Kawachi·K. Kawata·I. Kharuk·E. Kido·H. B. Kim·J. H. Kim·S. W. Kim·R. Kobo·I. Komae·K. Komatsu·K. Komori·A. Korochkin·C. Koyama·M. Kudenko·M. Kuroiwa·Y. Kusumori·M. Kuznetsov·Y. J. Kwon·K. H. Lee·M. J. Lee·B. Lubsandorzhiev·J. P. Lundquist·H. Matsushita·A. Matsuzawa·J. A. Matthews·J. N. Matthews·K. Mizuno·M. Mori·S. Nagataki·K. Nakagawa·M. Nakahara·H. Nakamura·T. Nakamura·T. Nakayama·Y. Nakayama·K. Nakazawa·T. Nonaka·S. Ogio·H. Ohoka·N. Okazaki·M. Onishi·A. Oshima·H. Oshima·S. Ozawa·I. H. Park·K. Y. Park·M. Potts·M. Przybylak·M. S. Pshirkov·J. Remington·C. Rott·G. I. Rubtsov·D. Ryu·H. Sagawa·N. Sakaki·R. Sakamoto·T. Sako·N. Sakurai·S. Sakurai·D. Sato·K. Sekino·T. Shibata·J. Shikita·H. Shimodaira·H. S. Shin·K. Shinozaki
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Abstract

Ultra-high-energy photons play an important role in probing astrophysical models and beyond-Standard-Model scenarios. We report updated limits on the diffuse photon flux using Telescope Array's Surface Detector data collected over 14 years of operation. Our method employs a neural network classifier to effectively distinguish between proton-induced and photon-induced events. The input data include both reconstructed composition-sensitive parameters and raw time-resolved signals registered by the Surface Detector stations. To mitigate biases from Monte Carlo simulations, we fine-tune the network with a subset of experimental data. The number of observed photon candidates is found to be consistent with the expected hadronic background, yielding upper limits on photon flux $\Phi_\gamma(E_\gamma > 10^{19} \text{eV}) < 2.3 \cdot 10^{-3} $, and $\Phi_\gamma(E_\gamma > 10^{20} \text{eV}) < 3.0 \cdot 10^{-4} $ $ (\text{km}^2 \cdot \text{sr} \cdot \text{yr})^{-1} $.

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Telescope Array Collaboration, R. U. Abbasi, T. Abu-Zayyad, M. Allen, J. W. Belz, D. R. Bergman, F. Bradfield, I. Buckland, W. Campbell, B. G. Cheon, K. Endo, A. Fedynitch, T. Fujii, K. Fujisue, K. Fujita, M. Fukushima, G. Furlich, A. Galvez Urena, Z. Gerber, N. Globus, T. Hanaoka, W. Hanlon, N. Hayashida, H. He, K. Hibino, R. Higuchi, D. Ikeda, D. Ivanov, S. Jeong, C. C. H. Jui, K. Kadota, F. Kakimoto, O. Kalashev, K. Kasahara, Y. Kawachi, K. Kawata, I. Kharuk, E. Kido, H. B. Kim, J. H. Kim, S. W. Kim, R. Kobo, I. Komae, K. Komatsu, K. Komori, A. Korochkin, C. Koyama, M. Kudenko, M. Kuroiwa, Y. Kusumori, M. Kuznetsov, Y. J. Kwon, K. H. Lee, M. J. Lee, B. Lubsandorzhiev, J. P. Lundquist, H. Matsushita, A. Matsuzawa, J. A. Matthews, J. N. Matthews, K. Mizuno, M. Mori, S. Nagataki, K. Nakagawa, M. Nakahara, H. Nakamura, T. Nakamura, T. Nakayama, Y. Nakayama, K. Nakazawa, T. Nonaka, S. Ogio, H. Ohoka, N. Okazaki, M. Onishi, A. Oshima, H. Oshima, S. Ozawa, I. H. Park, K. Y. Park, M. Potts, M. Przybylak, M. S. Pshirkov, J. Remington, C. Rott, G. I. Rubtsov, D. Ryu, H. Sagawa, N. Sakaki, R. Sakamoto, T. Sako, N. Sakurai, S. Sakurai, D. Sato, K. Sekino, T. Shibata, J. Shikita, H. Shimodaira, H. S. Shin, K. Shinozaki. 2025-12-01. Searching for EeV photons with Telescope Array Surface Detector and neural networks. https://arxiv.org/abs/2512.01638

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