Pushing the Energy and Cosmic Frontiers with High-Energy Astrophysical Neutrinos1

M Bustamante

doi:10.1088/1742-6596/1586/1/012041

Abstract

The astrophysical neutrinos recently discovered by the IceCube neutrino telescope have the highest detected neutrino energies — from TeV to PeV — and travel the longest distances — up to a few Gpc, the size of the observable Universe. These features make them naturally attractive probes of fundamental particle-physics properties, possibly tiny in size, at energy scales unreachable by any other means. The decades before the IceCube discovery saw many proposals of particle-physics studies in this direction. Today, those proposals have become a reality, in spite of prevalent astrophysical unknowns. We showcase examples of studying fundamental neutrino physics at these scales, including some of the most stringent tests of physics beyond the Standard Model.

Highlights

High-energy astroparticle physics has two complementary facets
We focus on the particle physics facet; in particular, on the unique strengths of high-energy astrophysical neutrinos to explore it
At (ii) They have the longest baselines: Even though the sources of high-energy astrophysical neutrinos remain undiscovered, the isotropy in their arrival directions hints at an origin in extragalactic sources located at Gpc-scale distances from Earth (1 Gpc ≈ 3 · 1022 km), essentially the size of the observable Universe

Summary

Introduction

High-energy astroparticle physics has two complementary facets. One facet is oriented to astrophysics [1]. We focus on the particle physics facet; in particular, on the unique strengths of high-energy astrophysical neutrinos to explore it. High-energy astrophysical neutrinos — so far detected in the TeV–PeV range — reach Earth without being attenuated. At (ii) They have the longest baselines: Even though the sources of high-energy astrophysical neutrinos remain undiscovered, the isotropy in their arrival directions hints at an origin in extragalactic sources located at Gpc-scale distances from Earth (1 Gpc ≈ 3 · 1022 km), essentially the size of the observable Universe. Numerous new-physics effects grow as ∼ κnEνnL, where κn is a model-specific coupling strengths, Eν is the neutrino energy, L is the propagation distance, and n is an integer that determines the energy-dependence of the effect. Using astrophysical PeV neutrinos coming from sources located Gpc away, we can probe tiny couplings, i.e., κn ∼ 4·10−47 (Eν/PeV)−n (L/Gpc)−1 PeV1−n, an improvement of several orders of magnitude over limits obtained using atmospheric neutrinos [6, 7]

Producing neutrinos

Findings

10 Geoneutrinos