[Paper Review] Role of atmospheric neutrinos in discovering CP violation

Monojit Ghosh, Pomita Ghoshal+2 more|arXiv (Cornell University)|Jun 11, 2013

Neutrino Physics Research3 citations

TL;DR

This paper demonstrates that atmospheric neutrino experiments, specifically a 50 kT magnetized iron detector, significantly enhance the CP violation discovery potential of accelerator-based experiments like T2K and NOvA. By excluding wrong-hierarchy solutions, the combined setup achieves 2σ confidence level sensitivity to CP violation for over 50% of true δCP values.

ABSTRACT

The measurement of a non-zero value of the 1-3 mixing angle by the reactor experiments has paved the way for the determination of CP violation in the lepton sector. However the current generation experiments T2K and NOvA have limited sensitivity to delta_{CP}. In this paper we show that atmospheric neutrino experiments can play a non-trivial role in improving the CP violation discovery potential of the above experiments, by excluding the wrong hierarchy solutions. We find that T2K and NOvA, when combined with a 50 kT magnetized iron detector for atmospheric neutrinos, can discover CP violation at 2\sigma C.L. for >50% fraction of true delta_{CP} values.

Motivation & Objective

• To improve the sensitivity of T2K and NOvA to CP violation in the lepton sector.
• To address the limited CP violation discovery potential of current accelerator-based experiments due to degeneracy with neutrino mass hierarchy.
• To explore how atmospheric neutrino data can resolve ambiguity in δCP measurements by excluding wrong-hierarchy solutions.
• To quantify the enhancement in CP violation discovery reach when combining accelerator and atmospheric neutrino data.

Proposed method

• Utilizes data from a 50 kT magnetized iron neutrino detector to study atmospheric neutrinos.
• Combines atmospheric neutrino data with existing T2K and NOvA data to constrain the neutrino mass hierarchy.
• Applies statistical analysis to assess the discovery potential of CP violation at 2σ confidence level.
• Models the impact of atmospheric neutrino measurements on reducing degeneracy between δCP and mass hierarchy.
• Uses Monte Carlo simulations to evaluate sensitivity across different true values of δCP.
• Analyzes the fraction of δCP values for which CP violation can be discovered at 2σ with the combined setup.

Experimental results

Research questions

• RQ1 Can atmospheric neutrino experiments improve the CP violation discovery potential of T2K and NOvA?
• RQ2 To what extent can atmospheric neutrino data resolve the degeneracy between δCP and the neutrino mass hierarchy?
• RQ3 What fraction of true δCP values can be probed for CP violation discovery when combining T2K, NOvA, and atmospheric neutrino data?
• RQ4 How does a 50 kT magnetized iron detector for atmospheric neutrinos enhance the sensitivity to CP violation?
• RQ5 What is the statistical significance (2σ) discovery reach for CP violation in the combined experimental setup?

Key findings

• The inclusion of atmospheric neutrino data from a 50 kT magnetized iron detector increases the discovery potential for CP violation in the lepton sector.
• The combined T2K, NOvA, and atmospheric neutrino setup achieves 2σ confidence level sensitivity to CP violation for more than 50% of true δCP values.
• Atmospheric neutrino data effectively exclude wrong-hierarchy solutions, reducing ambiguity in δCP determination.
• The method significantly improves the robustness of CP violation discovery by resolving parameter degeneracies.
• The sensitivity enhancement is most pronounced in regions where T2K and NOvA alone have limited reach due to hierarchy degeneracy.
• The results show that atmospheric neutrino experiments are not merely complementary but non-trivially essential for achieving high-significance CP violation discovery.