Extrinsic and Intrinsic CPT Asymmetries in Neutrino Oscillations

TL;DR

This paper analyzes extrinsic and intrinsic CPT asymmetries in neutrino oscillations, deriving conditions for vanishing asymmetries and exploring how experiments can constrain differences in CP-violating phases.

Contribution

It introduces analytical conditions for CPT asymmetry contours and assesses experimental prospects for constraining CP phase differences without assuming CPT symmetry.

Findings

Analytical conditions for vanishing extrinsic CPT asymmetries.

Constraints on phase difference |δ - δ̄| at 3σ level.

Potential to test CPT violation with neutrino experiments.

Abstract

We reconsider the extrinsic and possible intrinsic CPT violation in neutrino oscillations, and point out an identity, i.e., $A^{\rm CP}_{\alpha \beta} = A^{\rm CPT}_{\beta \alpha} + A^{\rm T}_{\alpha \beta}$, among the CP, T, and CPT asymmetries in oscillations. For three-flavor oscillations in matter of constant density, the extrinsic CPT asymmetries $A^{\rm CPT}_{ee}$, $A^{\rm CPT}_{e\mu}$, $A^{\rm CPT}_{\mu e}$, and $A^{\rm CPT}_{\mu \mu}$ caused by Earth matter effects have been calculated in the plane of different neutrino energies and baseline lengths. It is found that two analytical conditions can be implemented to describe the main structure of the contours of vanishing extrinsic CPT asymmetries. Finally, without assuming intrinsic CPT symmetry in the neutrino sector, we investigate the possibility to constrain the difference of the neutrino CP-violating phase $\delta$ and the antineutrino one $\overline{\delta}$ using a low-energy neutrino factory and the super-beam experiment ESS$\nu$SB. We find that $|\delta - \overline{\delta}| \lesssim 0.35\pi$ in the former case and $|\delta - \overline{\delta}| \lesssim 0.7\pi$ in the latter case can be achieved at the $3\sigma$ confidence level if $\delta = \overline{\delta} = \pi/2$ is assumed.