We present the results of the charge ratio ($R$) and polarization ($P^{ \mu}_{ 0}$) 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 $R=1.32 \pm 0.02$ $(\mathrm{ stat.}{ +}\mathrm{ syst.})$ at $E_{ \mu}\cos \theta_{ \mathrm{ Zenith}}=0.7^{ +0.3}_{ -0.2}$ $\mathrm{ TeV}$, where $E_{ \mu}$ is the muon energy and $\theta_{ \mathrm{ Zenith}}$ 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 $\pi K$ model of $1.9\sigma$. We also measured the muon polarization at the production location to be $P^{ \mu}_{ 0}=0.52 \pm 0.02$ $(\mathrm{ stat.}{ +}\mathrm{ syst.})$ at the muon momentum of $0.9^{ +0.6}_{ -0.1}$ $\mathrm{ TeV}/c$ at the surface of the mountain; this also suggests a tension with the Honda flux model of $1.5\sigma$. This is the most precise measurement ever to experimentally determine the cosmic-ray muon polarization near $1~\mathrm{ TeV}/c$. These measurement results are useful to improve the atmospheric neutrino simulations.
Categories: hep-ex astro-ph.HE