Demonstrating the ability of IceCube DeepCore to probe Earth's interior with atmospheric neutrino oscillations

TL;DR

This work investigates whether atmospheric neutrinos traversing Earth can reveal measurable matter effects that illuminate Earth's interior. It uses IceCube DeepCore's GeV-scale sensitivity to oscillation modifications caused by the electron density profile, including MSW and parametric resonances, and compares density profiles via Asimov sensitivity studies against the PREM model. The analysis employs MC reweighting of events by oscillation probabilities under different density models and executes both non-nested tests (matter effects vs vacuum) and nested tests (Earth mass via a scaling factor $\alpha$ and correlated layer densities via $\alpha^c$), with external priors on mass and moment of inertia. The main contributions are establishing Earth matter effects with DeepCore, validating the non-uniform density distribution inside Earth, and constraining Earth's mass and layer densities, offering a neutrino-based tomography complement to seismic methods and promising improved precision with the forthcoming IceCube Upgrade.

Abstract

The IceCube Neutrino Observatory is an optical Cherenkov detector instrumenting one cubic kilometer of ice at the South Pole. The Cherenkov photons emitted following a neutrino interaction are detected by digital optical modules deployed along vertical strings within the ice. The densely instrumented bottom central region of the IceCube detector, known as DeepCore, is optimized to detect GeV-scale atmospheric neutrinos. As upward-going atmospheric neutrinos pass through Earth, matter effects alter their oscillation probabilities due to coherent forward scattering with ambient electrons. These matter effects depend upon the energy of neutrinos and the density distribution of electrons they encounter during their propagation. Using simulated data at the IceCube Deepcore equivalent to its 9.3 years of observation, we demonstrate that atmospheric neutrinos can be used to probe the broad features of the Preliminary Reference Earth Model. In this contribution, we present the preliminary sensitivities for establishing the Earth matter effects, validating the non-homogeneous distribution of Earth's electron density, and measuring the mass of Earth. Further, we also show the DeepCore sensitivity to perform the correlated density measurement of different layers incorporating constraints on Earth's mass and moment of inertia.

Figures (6)

• Figure 1: Left: Radial distribution of Earth's density using the 12-layered PREM model. Right: Various profiles of radial density distribution inside Earth such as 12-layered and 5-layered PREM profiles, and a uniform density profile.
• Figure 2:
• Figure 3: Schematic image of the IceCube Neutrino Observatory, which includes the main IceCube detector, a denser array called DeepCore for low-energy neutrino detection, and a surface detector array known as IceTop for atmospheric muon veto.
• Figure 4: The expected number of events based on the 12-layered PREM profile of Earth, as a function of reconstructed energy and $\cos\theta_\text{zenith}$ of neutrino for each PID in 9.3 years of lifetime. Each histogram represents one PID bin, defined by the PID boundaries. The boundaries of PID bins are 0 to 0.33 for cascades, 0.33 to 0.39 for mixed, and 0.39 to 1 for tracks.
• Figure 5: Left: Asimov sensitivity as a function of simulated $\sin^2\theta_{23}$ (true) to establish Earth matter effects in atmospheric neutrino oscillations by rejecting the vacuum oscillations with respect to oscillations in the presence of Earth's matter. Right: Asimov sensitivity as a function of simulated $\sin^2\theta_{23}$ (true) to validate the layered structure inside Earth by rejecting the uniform matter density profile with respect to the PREM density profile.