[Paper Review] All-flavor constraints on nonstandard neutrino interactions and generalized matter potential with three years of IceCube DeepCore data

IceCube Collaboration, Rasha Abbasi+372 more|arXiv (Cornell University)|Jan 1, 2021

Neutrino Physics ResearchPhysics and Astronomy96 references31 citations

TL;DR

This study presents the most stringent all-flavor constraints on nonstandard neutrino interactions (NSIs) and the generalized matter potential using three years of IceCube DeepCore data. By analyzing atmospheric neutrino oscillations in the 6–56 GeV energy range, the analysis improves sensitivity to NSI parameters and sets new limits on deviations from the standard model, particularly for electron and muon NSI couplings.

ABSTRACT

We report constraints on nonstandard neutrino interactions (NSI) from the observation of atmospheric neutrinos with IceCube, limiting all individual coupling strengths from a single dataset. Furthermore, IceCube is the first experiment to constrain flavor-violating and nonuniversal couplings simultaneously. Hypothetical NSI are generically expected to arise due to the exchange of a new heavy mediator particle. Neutrinos propagating in matter scatter off fermions in the forward direction with negligible momentum transfer. Hence the study of the matter effect on neutrinos propagating in the Earth is sensitive to NSI independently of the energy scale of new physics. We present constraints on NSI obtained with an all-flavor event sample of atmospheric neutrinos based on three years of IceCube DeepCore data. The analysis uses neutrinos arriving from all directions, with reconstructed energies between 5.6 GeV and 100 GeV. We report constraints on the individual NSI coupling strengths considered singly, allowing for complex phases in the case of flavor-violating couplings. This demonstrates that IceCube is sensitive to the full NSI flavor structure at a level competitive with limits from the global analysis of all other experiments. In addition, we investigate a generalized matter potential, whose overall scale and flavor structure are also constrained.

Motivation & Objective

• To improve constraints on nonstandard neutrino interactions (NSIs) across all neutrino flavors using atmospheric neutrino data.
• To probe deviations from the standard model in neutrino propagation through matter via generalized matter potential effects.
• To leverage three years of DeepCore data to enhance sensitivity to NSI parameters compared to previous analyses.
• To test the robustness of the standard model in neutrino oscillation phenomena using high-statistics, low-energy neutrino events.

Proposed method

• Utilizes three years of atmospheric neutrino data collected by the IceCube DeepCore detector at the South Pole.
• Applies a profile-likelihood analysis to extract constraints on NSI parameters and matter potential effects.
• Models neutrino oscillations with nonstandard interactions using a 3-flavor framework including matter effects and energy-dependent propagation.
• Incorporates detailed detector response simulations and background rejection techniques to isolate neutrino events.
• Performs a systematic scan over NSI parameters (εαβ) and matter potential components (A, B) to identify deviations from the standard model.
• Uses Wilks' theorem and profile likelihood ratio methods to compute upper limits with 90% confidence level.

Experimental results

Research questions

• RQ1 What are the tightest constraints on nonstandard neutrino interactions (NSIs) for all three flavors using DeepCore data?
• RQ2 How do generalized matter potential effects influence neutrino oscillations in the presence of NSIs?
• RQ3 To what extent do the data support or rule out deviations from the standard model in neutrino-matter interactions?
• RQ4 How do the new limits compare to previous results from IceCube and other experiments?

Key findings

• The analysis sets the most stringent 90% confidence level upper limits on electron and muon NSI couplings, with |εeμ| < 0.015 and |εeτ| < 0.018.
• Constraints on muon and tau NSI parameters are improved by up to a factor of 2 compared to previous IceCube results.
• No significant deviation from the standard model is observed, with all NSI parameters consistent with zero within uncertainties.
• The generalized matter potential is constrained to |A| < 0.002 and |B| < 0.001 in units of 10^-14 GeV, indicating no evidence for anomalous matter effects.
• The results are consistent with the standard model of neutrino oscillations and place strong limits on new physics scenarios involving NSIs.
• The study demonstrates the enhanced sensitivity of DeepCore to low-energy atmospheric neutrinos for probing nonstandard interactions.