Measurements of the charge ratio and polarization of cosmic-ray muons with the Super-Kamiokande detector

• Published in: Physical review. D 2024-10, Vol.110 (8), Article 082008
• Main Authors: Kitagawa, H., Tada, T., Abe, K., Bronner, C., Hayato, Y., Hiraide, K., Hosokawa, K., Ieki, K., Ikeda, M., Kameda, J., Kanemura, Y., Kaneshima, R., Kashiwagi, Y., Kataoka, Y., Miki, S., Mine, S., Miura, M., Moriyama, S., Nakahata, M., Nakano, Y., Nakayama, S., Noguchi, Y., Okamoto, K., Sato, K., Sekiya, H., Shiba, H., Shimizu, K., Shiozawa, M., Sonoda, Y., Suzuki, Y., Takeda, A., Takemoto, Y., Takenaka, A., Tanaka, H., Watanabe, S., Yano, T., Han, S., Kajita, T., Okumura, K., Tashiro, T., Tomiya, T., Wang, X., Yoshida, S., Megias, G. D., Fernandez, P., Labarga, L., Ospina, N., Zaldivar, B., Kearns, E., Raaf, J. L., Wan, L., Wester, T., Pointon, B. W., Bian, J., Griskevich, N. J., Locke, S., Smy, M. B., Sobel, H. W., Takhistov, V., Yankelevich, A., Hill, J., Jang, M. C., Lee, S. H., Moon, D. H., Park, R. G., Bodur, B., Scholberg, K., Walter, C. W., Beauchêne, A., Drapier, O., Giampaolo, A., Mueller, Th. A., Paganini, P., Quilain, B., Rogly, R., Santos, A. D., Nakamura, T., Jang, J. S., Machado, L. N., Learned, J. G., Choi, K., Iovine, N., Cao, S., Anthony, L. H. V., Marin, D., Prouse, N. W., Scott, M., Sztuc, A. A., Uchida, Y., Berardi, V., Calabria, N. F., Catanesi, M. G., Radicioni, E., Langella, A., De Rosa, G., Collazuol, G., Iacob, F., Lamoureux, M., Mattiazzi, M., Ludovici, L.
• Format: Article
• Language: English
• Subjects: Astrophysics; High Energy Physics - Experiment; Physics
• ISSN: 2470-0010; 2470-0029
• DOI: 10.1103/PhysRevD.110.082008

We present the results of the charge ratio ( R ) and polarization ( P 0 μ ) measurements using decay electron events collected between September 2008 and June 2022 with the Super-Kamiokande detector. Because of its underground location and long operation, we are able to perform high-precision measurements by accumulating cosmic-ray muons. We measured the muon charge ratio to be R = 1.32 ± 0.02 ( stat + syst ) at E μ cos θ Zenith = 0.7 − 0.2 + 0.3 TeV , where E μ is the muon energy and θ Zenith is the zenith angle of incoming cosmic-ray muons. This result is consistent with the Honda flux model while indicating a tension with the π K model of 1.9 σ . We also measured the muon polarization at the production location to be P 0 μ = 0.52 ± 0.02 ( stat + syst ) at the muon momentum of 0.9 − 0.1 + 0.6 TeV / c at the surface of the mountain; this also suggests a tension with the Honda flux model of 1.5 σ . This is the most precise measurement ever to experimentally determine the cosmic-ray muon polarization near 1 TeV / c . These measurement results are useful to improve atmospheric neutrino simulations.