We present a search for solar axions produced through the axion-electron coupling $(g_{ae})$ using data from a novel 7-GridPix detector installed at the CERN Axion Solar Telescope (CAST). The detector, featuring ultra-thin silicon nitride windows and multiple veto systems, collected approximately 160 hours of solar tracking data between 2017-2018. Using machine learning techniques and the veto systems, we achieved a background rate of $1.06\times 10^{-5}\,\text{keV}^{-1}\text{cm}^{-2}\text{s}^{-1}$ at a signal efficiency of about $80\,\%$ in the $0.2$-$8\,\text{keV}$ range. Analysis of the data yielded no significant excess above background, allowing us to set a new upper limit on the product of the axion-electron and axion-photon couplings of $g_{ae}\cdot g_{aγ} < 7.35\times 10^{-23}\,\text{GeV}^{-1}$ at $95\,\%$ confidence level. This result improves upon the previous best helioscope limit and demonstrates the potential of GridPix technology for rare event searches. Additionally, we derived a limit on the axion-photon coupling of $g_{aγ} < 9.0\times 10^{-11}\,\text{GeV}^{-1}$ at $95\,\%$ CL, which, while not surpassing CAST's best limit, provides complementary constraints on axion models.
Search for solar axions produced through the axion-electron coupling $g_{ae}$ using a new GridPix detector at CAST / Altenmüller, K.; Anastassopoulos, V.; Arguedas-Cuendis, S.; Aune, S.; Baier, J.; Barth, K.; Bräuninger, H.; Cantatore, G.; Caspers, F.; Castel, J. F.; Çetin, S. A.; Christensen, F.; Cogollos, C.; Dafni, T.; Davenport, M.; Decker, T. A.; Desch, K.; Díez-Ibáñez, D.; Döbrich, B.; Ferrer-Ribas, E.; Fischer, H.; Funk, W.; Galán, J.; García, J. A.; Gardikiotis, A.; Giomataris, I.; Golm, J.; Hailey, C. H.; Hasinoff, M. D.; Hoffmann, D. H. H.; Irastorza, I. G.; Jacoby, J.; Jakobsen, A. C.; Jakovčić, K.; Kaminski, J.; Karuza, M.; Kostoglou, S.; Krieger, C.; Laurent, J. M.; Luzón, G.; Malbrunot, C.; Margalejo, C.; Maroudas, M.; Miceli, L.; Mirallas, H.; Navarro, P.; Obis, L.; Özbey, A.; Özbozduman, K.; Papaevangelou, T.; Pérez, O.; Pivovaroff, M. J.; Rosu, M.; Ruiz-Chóliz, E.; Ruz, J.; Schiffer, T.; Schmidt, S.; Schumann, M.; Semertzidis, Y. K.; Solanki, S. K.; Stewart, L.; Vafeiadis, T.; Vogel, J. K.; Zioutas, K.. - ELETTRONICO. - (2025 Aug 19), pp. ---.
Search for solar axions produced through the axion-electron coupling $g_{ae}$ using a new GridPix detector at CAST
G. Cantatore;
2025-08-19
Abstract
We present a search for solar axions produced through the axion-electron coupling $(g_{ae})$ using data from a novel 7-GridPix detector installed at the CERN Axion Solar Telescope (CAST). The detector, featuring ultra-thin silicon nitride windows and multiple veto systems, collected approximately 160 hours of solar tracking data between 2017-2018. Using machine learning techniques and the veto systems, we achieved a background rate of $1.06\times 10^{-5}\,\text{keV}^{-1}\text{cm}^{-2}\text{s}^{-1}$ at a signal efficiency of about $80\,\%$ in the $0.2$-$8\,\text{keV}$ range. Analysis of the data yielded no significant excess above background, allowing us to set a new upper limit on the product of the axion-electron and axion-photon couplings of $g_{ae}\cdot g_{aγ} < 7.35\times 10^{-23}\,\text{GeV}^{-1}$ at $95\,\%$ confidence level. This result improves upon the previous best helioscope limit and demonstrates the potential of GridPix technology for rare event searches. Additionally, we derived a limit on the axion-photon coupling of $g_{aγ} < 9.0\times 10^{-11}\,\text{GeV}^{-1}$ at $95\,\%$ CL, which, while not surpassing CAST's best limit, provides complementary constraints on axion models.Pubblicazioni consigliate
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