[Paper Review] Impact of Matter Density Profile Shape on Non-Standard Interactions at DUNE

A. Chatterjee, F. Kamiya+2 more|arXiv (Cornell University)|Sep 25, 2018

Neutrino Physics Research36 references4 citations

TL;DR

This paper investigates how variations in Earth's matter density profile affect the sensitivity to non-standard neutrino interactions (NSI) at the Deep Underground Neutrino Experiment (DUNE). Using analytical and numerical methods, it shows that for specific NSI parameters—particularly involving the complex phase $φ_{e\tau}$—differences in matter profiles can lead to event rate discrepancies of up to 30–40σ in the $ν_e$ appearance channel, significantly impacting NSI discovery potential.

ABSTRACT

We discuss the impact of matter density profile shape on the determination of nonstandard neutrino matter interactions (NSI) in the context of the long baseline accelerator experiments such as Deep Underground Neutrino Experiment (DUNE). The primary scientific goals of DUNE are to determine the neutrino mass hierarchy, the leptonic CP violation phase, and the existence of new physics beyond the standard model of particles. Here we study the role of different earth matter density profiles on the question of observing standard oscillation as wells as NSI at DUNE. We consider two different earth matter density profiles which are relevant for the DUNE baseline. We first discuss the impact of matter on both appearance and disappearance oscillation channels, then we demonstrate the effect of different matter density profiles on the determination of NSI. We consider four different scenarios of NSI and elucidate the effect at the oscillation probability and measurement of number of events at DUNE. In one case of study we show that a nonstandard complex phase $ϕ_{eτ}$ could significantly increase the sensitivity to different matter distributions along the baseline.

Motivation & Objective

• To assess the impact of different Earth matter density profiles on the detection of non-standard neutrino interactions (NSI) at DUNE.
• To evaluate whether uncertainties in matter density profiles could lead to misinterpretations in NSI parameter measurements.
• To determine under which NSI scenarios the choice of matter profile becomes critical for event rate predictions.
• To investigate the role of the non-standard phase $\phi_{e\tau}$ in amplifying sensitivity differences between profiles.
• To clarify the necessity of precise matter density modeling for resolving degeneracies in NSI and neutrino mass hierarchy measurements.

Proposed method

• The study uses two distinct matter density profiles—PREM (Preliminary Reference Earth Model) and SR (Simplified Reference model)—to compute neutrino oscillation probabilities at DUNE.
• Analytical expressions for appearance and disappearance channel probabilities are derived, incorporating both standard oscillation parameters and NSI parameters ($\varepsilon_{\alpha\beta}$).
• The Hamiltonian formalism is applied to model neutrino propagation through matter, including effective potentials due to coherent forward scattering.
• Event rates at the DUNE detector are simulated for different NSI scenarios and matter profiles, with statistical significance quantified via $\Delta N / \sigma$.
• The uncertainty in event counts is calculated as $\sigma = \sqrt{\sigma_{\text{PREM}}^2 + \sigma_{\text{SR}}^2}$, enabling comparison of profile-dependent deviations.
• Sensitivity is evaluated by computing the ratio $\Delta N / \sigma$ across energy bins, identifying regions of high distinguishability between profiles.

Experimental results

Research questions

• RQ1 How do different Earth matter density profiles affect the predicted event rates for neutrino appearance and disappearance channels at DUNE?
• RQ2 To what extent do non-standard interactions (NSI) amplify the sensitivity to matter density profile uncertainties?
• RQ3 In which NSI parameter scenarios is the difference in event rates between PREM and SR profiles most pronounced?
• RQ4 How does the non-standard phase $\phi_{e\tau}$ influence the detectability of matter profile effects in NSI measurements?
• RQ5 Can matter profile uncertainties lead to false interpretations or degeneracies in NSI parameter space, particularly in the context of mass hierarchy determination?

Key findings

• For Case 3 in Table 2—featuring $\varepsilon_{e\mu}$ and $\varepsilon_{e\tau}$—the difference in event counts between PREM and SR matter profiles reaches up to $30-40~\sigma$ in the $\nu_e$ appearance channel for normal hierarchy at 2–3 GeV.
• The sensitivity to matter profile differences peaks when $\phi_{e\tau} \approx \pi/3$, where $\Delta N / \sigma \approx 38$, indicating a strong dependence on the NSI phase.
• In contrast, when $\phi_{e\tau} \approx -\pi/3$, the difference $\Delta N \approx 0$, showing a near-cancellation effect that masks profile sensitivity.
• For both normal and inverted hierarchies, $|\Delta N| \approx 4\sigma$ is observed in the $\nu_\mu$ disappearance channel at ~2.5 GeV, indicating measurable but less dramatic differences.
• The study confirms that matter density profile uncertainty can significantly affect NSI sensitivity, especially when off-diagonal NSI parameters are non-zero.
• The results emphasize that precise matter density modeling is essential to avoid degeneracies in NSI parameter determination and to ensure robust discovery claims.