Observation of Cosmic-Ray Anisotropy in the Southern Hemisphere with 12 yr of Data Collected by the IceCube Neutrino Observatory

TL;DR

This study presents a detailed analysis of cosmic-ray anisotropy in the Southern Hemisphere using 12 years of IceCube data, revealing energy-dependent changes in cosmic-ray arrival directions with high statistical precision.

Contribution

It provides the first comprehensive, high-precision measurement of cosmic-ray anisotropy in the Southern Hemisphere over a full solar cycle with improved systematic uncertainty control.

Findings

Confirmed change in anisotropy structure between 10 TeV and 1 PeV

Observed anisotropy variation in the 100-300 TeV energy range

Achieved unprecedented statistical accuracy in cosmic-ray arrival directions

Abstract

We analyzed the 7.92$\times 10^{11}$ cosmic-ray-induced muon events collected by the IceCube Neutrino Observatory from May 13, 2011, when the fully constructed experiment started to take data, to May 12, 2023. This dataset provides an up-to-date cosmic-ray arrival direction distribution in the Southern Hemisphere with unprecedented statistical accuracy covering more than a full period length of a solar cycle. Improvements in Monte Carlo event simulation and better handling of year-to-year differences in data processing significantly reduce systematic uncertainties below the level of statistical fluctuations compared to the previously published results. We confirm the observation of a change in the angular structure of the cosmic-ray anisotropy between 10 TeV and 1 PeV, more specifically in the 100-300 TeV energy range.