[Paper Review] Probing high-energy interactions of atmospheric and astrophysical neutrinos

S. R. Klein|arXiv (Cornell University)|Jun 5, 2019

Astrophysics and Cosmic Phenomena4 citations

TL;DR

This paper investigates high-energy neutrino interactions in atmospheric and astrophysical contexts using large-scale neutrino observatories like IceCube, KM3NeT, and future facilities such as IceCube-Gen2 and RNO. It demonstrates that these detectors can probe neutrino cross-sections and inelasticity at energies up to 10^20 eV—far beyond accelerator reach—offering unique sensitivity to both Standard Model physics at low Bjorken-x and beyond-Standard Model phenomena.

ABSTRACT

Astrophysical and atmospheric neutrinos are important probes of the powerful accelerators that produce cosmic-rays with EeV energies. Understanding these accelerators is a key goal of neutrino observatories, along with searches for neutrinos from supernovae, from dark matter annihilation, and other astrophysics topics. Here, we discuss how neutrino observatories like IceCube and future facilities like KM3NeT and IceCube-Gen2 can study the properties of high-energy (above 1 TeV) neutrino interactions. This is far higher than is accessible at man-made accelerators, where the highest energy neutrino beam reached only 500 GeV. In contrast, neutrino observatories have observed events with energies above 5 PeV - 10,000 times higher in energy - and future large observatories may probe neutrinos with energies up to $10^{20}$ eV. These data have implications for both Standard Model measurements, such as of low Bjorken$-x$ parton distributions and gluon shadowing, and also for searches for beyond Standard Model physics. This chapter will review the existing techniques and results, and discuss future prospects.

Motivation & Objective

• To study high-energy neutrino interactions (above 1 TeV) in natural sources like atmospheric and astrophysical neutrinos, which reach energies 10,000× higher than accelerator beams.
• To address the challenge of limited detector granularity and beam knowledge in measuring neutrino cross-sections and inelasticity at extreme energies.
• To evaluate the potential of radio-detection techniques (e.g., RNO, ARIA, GRAND) to extend energy reach below 10^17 eV and enable new physics measurements.
• To assess the sensitivity of future observatories to low Bjorken-x parton distributions and gluon shadowing in the proton.
• To explore the feasibility of detecting beyond-Standard Model physics through neutrino cross-section and inelasticity measurements at energies inaccessible to the LHC.

Proposed method

• Utilizes neutrino telescopes such as IceCube and KM3NeT to detect high-energy neutrino interactions via Cherenkov radiation from secondary particles.
• Analyzes event topologies—tracks (from νμ/ν̄μ CC interactions) and cascades (from νe/ν̄e CC and NC interactions)—to infer neutrino energy and flavor.
• Employs inelasticity distributions (fraction of energy transferred to target nucleus) as a probe of interaction dynamics and potential new physics.
• Leverages the Glashow resonance (ν̄e e → W−) at ~5 PeV to identify antineutrino events and improve flavor separation.
• Applies radio-detection techniques using phased-array triggers and large-scale antenna arrays (e.g., RNO, ARIA, GRAND) to detect coherent radio emission from particle showers in ice or rock.
• Uses the Landau-Pomeranchuk-Migdal (LPM) effect to distinguish electromagnetic subshowers from hadronic showers, enabling inelasticity measurements via shower structure.

Experimental results

Research questions

• RQ1 How can neutrino telescopes extend the measurement of neutrino cross-sections to energies above 1 TeV, where accelerator data are unavailable?
• RQ2 To what extent can inelasticity distributions at high energies probe low Bjorken-x parton distributions and gluon shadowing in the proton?
• RQ3 Can radio-detection techniques with phased-array triggers achieve sufficient energy resolution and threshold (down to 10^16 eV) to measure neutrino cross-sections and inelasticity?
• RQ4 What is the sensitivity of future observatories like IceCube-Gen2 and KM3NeT 2.0 to beyond-Standard Model physics at energy scales beyond the LHC?
• RQ5 Can the LPM effect be exploited to separate electromagnetic subshowers from hadronic showers, enabling improved inelasticity measurements in large radio arrays?

Key findings

• Neutrino observatories like IceCube have detected events with energies exceeding 5 PeV, extending the accessible energy range by a factor of 10,000 over accelerator-based experiments.
• The Glashow resonance at ~5 PeV provides a unique tool to identify ν̄e events and improve antineutrino separation, though only one or two such events have been observed so far.
• Future radio-detection arrays such as RNO and ARIA aim to observe astrophysical neutrinos down to ~10^16 eV, with RNO using phased-array triggers to enhance sensitivity.
• The LPM effect may enable separation of electromagnetic subshowers from hadronic showers in large, granular radio arrays, offering a path to inelasticity measurements at the highest energies.
• IceCube-Gen2 and KM3NeT 2.0 are expected to extend inelasticity measurements to at least 1 PeV, enabling tests of new physics at moderate mass scales.
• A future 300,000-antenna array like GRAND could achieve sufficient statistics to measure neutrino cross-sections with ~20% precision, probing physics beyond the LHC at scales above 10^16 GeV.