CP-Violating Neutrino Nonstandard Interactions in Long-Baseline-Accelerator Data.

Area of Science:

• Particle Physics
• Astrophysics
• Cosmology

Background:

• Neutrino oscillations are a key phenomenon for understanding fundamental particle physics.
• Nonstandard Interactions (NSI) in neutrinos offer a potential window into new physics beyond the Standard Model.
• Long-baseline neutrino experiments like NOvA and T2K provide crucial data for studying oscillation parameters.

Purpose of the Study:

• To investigate the presence of CP-violating neutrino nonstandard interactions (NSI) using appearance data from NOvA and T2K.
• To analytically approximate expected NSI parameters and resolve differences between experiments.
• To compare long-baseline results with constraints from other experiments like IceCube and COHERENT.

Main Methods:

• Analysis of neutrino appearance data from the NOvA and T2K experiments.
• Analytical approximation of NSI parameters to reconcile experimental discrepancies.
• Combination of data from multiple experiments to constrain NSI parameters.

Main Results:

• A tantalizing hint of CP-violating NSI was observed.
• A new complex phase, close to maximal CP violation (ϕ_{eμ} or ϕ_{eτ}≈3π/2), with magnitudes |ε_{eμ}| or |ε_{eτ}|∼0.2, is preferred.
• Comparison with IceCube and COHERENT data provides complementary constraints.

Conclusions:

• The findings suggest the existence of new physics influencing neutrino oscillations.
• CP-violating NSI could be a significant factor in understanding neutrino behavior.
• Further data from current and future experiments are needed to confirm these hints.