[Paper Review] IceCube - Astrophysics and Astroparticle Physics at the South Pole

The IceCube Collaboration|arXiv (Cornell University)|Nov 22, 2011

Astrophysics and Cosmic Phenomena4 citations

TL;DR

This paper presents the completion and initial scientific performance of the IceCube Neutrino Observatory at the South Pole, demonstrating its sensitivity to high-energy cosmic neutrinos, atmospheric and astrophysical neutrinos, and transient events like supernovae and solar flares. Key results include limits on diffuse neutrino fluxes within a factor of 2.5 of the Waxman-Bahcall bound and stringent constraints on WIMPs and magnetic monopoles, with DeepCore enabling low-energy neutrino studies.

ABSTRACT

The IceCube Neutrino Observatory at the South Pole has been completed in December 2010. In this paper we describe the final detector and report results on physics and performance using data taken at different stages of the yet incomplete detector. No signals for cosmic neutrinos from point sources and diffuse fluxes have been found. Prospects of these searches, including the setup of multi-messenger programs, are discussed. The limits on neutrinos from GRBs, being far below model predictions, require a reevaluation of GRB model assumptions. Various measurements of cosmic ray properties have been obtained from atmospheric muon and neutrino spectra and from air shower measurements; these results will have an important impact on model developments. IceCube observed an anisotropy of cosmic rays on multiple angular scales, for the first time in the Southern sky. The unique capabilities of IceCube for monitoring transient low energy events are briefly discussed. Finally an outlook to planned extensions is given which will improve the sensitivities both on the low and high energy side.

Motivation & Objective

• To present the scientific performance and initial results of the completed IceCube Neutrino Observatory.
• To demonstrate IceCube's sensitivity to high-energy cosmic neutrinos and transient astrophysical events such as supernovae and gamma-ray bursts.
• To report on constraints for exotic particles including WIMPs and magnetic monopoles.
• To highlight IceCube's role in advancing cosmic ray and atmospheric neutrino physics.
• To outline future extensions, including DeepCore and potential low-energy and radio/acoustic upgrades.

Proposed method

• Utilizes a cubic kilometer of Antarctic ice instrumented with 5,160 optical sensors (DOMs) to detect Cherenkov radiation from charged particles produced by neutrino interactions.
• Employs IceTop, a surface array of 81 stations, to detect cosmic ray air showers and measure their energy and arrival direction.
• Applies advanced trigger and data acquisition systems to identify rare high-energy events, including cascades and through-going muons.
• Uses time- and direction-dependent analysis techniques to search for point sources and transient signals such as supernovae.
• Applies multi-messenger follow-up strategies with optical, X-ray, and gamma-ray telescopes to enhance source detection significance.
• Employs energy reconstruction and angular resolution techniques to study atmospheric and cosmic neutrino fluxes.

Experimental results

Research questions

• RQ1 What is the sensitivity of IceCube to diffuse cosmic neutrino fluxes, and how does it compare to theoretical predictions such as the Waxman-Bahcall bound?
• RQ2 Can IceCube detect high-energy neutrinos from transient sources such as supernovae or gamma-ray bursts?
• RQ3 What constraints can IceCube place on the existence of weakly interacting massive particles (WIMPs) and magnetic monopoles?
• RQ4 How well can IceCube measure the composition and anisotropy of cosmic rays in the Southern Hemisphere?
• RQ5 What is the potential of DeepCore and future low-energy extensions for probing neutrino oscillations and proton decay?

Key findings

• IceCube's diffuse neutrino flux limits are now within a factor of 2.5 of the Waxman-Bahcall bound, indicating sensitivity to the most relevant theoretical predictions.
• The IC40+59 limit on gamma-ray burst (GRB) neutrino flux is 5 times below the model prediction of [16], challenging existing GRB models.
• WIMP mass limits between 50 GeV and 5 TeV are now in regions not excluded by direct detection experiments, providing unique constraints.
• Magnetic monopole limits are nearly 1,000 times below the Parker Bound, placing strong constraints on grand unified theories (GUTs).
• DeepCore has enabled access to low-energy neutrino physics, including the study of atmospheric neutrino 'prompt' components and neutrino oscillations.
• IceCube has observed cosmic ray anisotropies in the Southern sky for the first time, though their origin remains unexplained.