New Upper Limit on the Axion-Photon Coupling with an Extended CAST Run with a Xe-Based Micromegas Detector
K. Altenmüller, V. Anastassopoulos, S. Arguedas-Cuendis, S. Aune, J. Baier, K. Barth, H. Bräuninger, G. Cantatore, F. Caspers, J. Castel, S. A. Çetin, Finn E. Christensen, C. Cogollos, T. Dafní, M. Davenport, Todd A. Decker, K. Desch, D. Díez-Ibáñez, Babette Döbrich, E. Ferrer-Ribas, H. Fischer, W. Funk, J. Galán, José Miguel Alonso Garcia, A. Gardikiotis, I. Giomataris, J. Golm, Charles J. Hailey, M. D. Hasinoff, D. H. H. Hoffmann, I.G. Irastorza, J. Jacoby, Anders C. Jakobsen, K. Jakovčić, J. Kamiński, M. Karuza, S. Kostoglou, C. Krieger, B. Lakić, Jean‐Paul Laurent, G. Luzón, C. Malbrunot, C. Margalejo, Marios Maroudas, L. Miceli, H. Mirallas, P. Navarro, L. Obis, A. Özbey, K. Özbozduman, T. Papaevangelou, Óscar Cano Pérez, M. J. Pivovaroff, M. Rosu, Elisa Ruiz-Chóliz, J. Ruz, Sebastian Schmidt, M. Schümann, Yannis K. Semertzidis, S. K. Solanki, L. Stewart, T. Vafeiadis, J. K. Vogel, K. Zioutas
Abstract
Hypothetical axions provide a compelling explanation for dark matter and could be emitted from the hot solar interior. The CERN Axion Solar Telescope has been searching for solar axions via their back conversion to x-ray photons in a 9-T 10-m long magnet directed toward the Sun. We report on an extended run with the International Axion Observatory pathfinder detector, doubling the previous exposure time. The detector was operated with a xenon-based gas mixture for part of the new run, providing technical insights for future configurations. No counts were detected in the 95% signal-encircling region during the new run, while 0.75 were expected. The new data improve the axion-photon coupling limit to 5.8×10^{-11} GeV^{-1} at 95% CL (for m_{a}≲0.02 eV), the most restrictive experimental limit to date.