Testing the Pointing of IceCube using the Moon Shadow in Cosmic-Ray Induced Muons

TL;DR

This paper uses the moon shadow effect in cosmic-ray muons detected by IceCube to calibrate and verify the detector's pointing accuracy, employing improved analysis methods and new reconstruction algorithms.

Contribution

It introduces an enhanced moon shadow analysis with a larger detector, improved modeling, and verifies two new muon reconstruction algorithms for better directional accuracy.

Findings

Increased significance of moon shadow detection with improved methods

Validation of two new muon reconstruction algorithms

Effective calibration of IceCube's pointing accuracy

Abstract

The IceCube Neutrino Observatory is a cubic-kilometer-scaled detector located at the Geographic South Pole. The calibration of the directional reconstruction of neutrino-induced muons and the pointing accuracy of the detector have to be verified. For these purposes, the moon is used as a standard candle to not rely exclusively on simulated data: Cosmic rays get absorbed by the moon, which leads to a deficit of cosmic-ray-induced muons from the lunar direction that is measured with high statistics. The moon shadow analysis uses an unbinned maximum-likelihood method, which has been methodically improved, and uses a larger detector compared to previous analyses. This allows to observe the shadow with a large significance per month. In the first part, it is found that incorporating a moon disk model, a coordinate-dependent uncertainty scaling and an improved background estimation increase the significance compared to a previous more simplistic analysis. In the second part, the performance of two new directional muon reconstruction algorithms is verified.