Measurements of the Charge Ratio and Polarization of Cosmic-Ray Muons with the Super-Kamiokande Detector

We present the results of the charge ratio (R) and polarization (P^μ_0) measurements using the decay electron events collected from 2008 September to 2022 June by the Super-Kamiokande detector. Because of its underground location and long operation, we performed 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_μcosθ_Zenith=0.7^+0.3_-0.2 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 this suggests a tension with the π K model of 1.9σ. We also measured the muon polarization at the production location to be P^μ_0=0.52 ± 0.02 (stat.+syst.) at the muon momentum of 0.9^+0.6_-0.1 TeV/c at the surface of the mountain; this also suggests a tension with the Honda flux model of 1.5σ. 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 the atmospheric neutrino simulations.