Testing the RG Running of the Leptonic Dirac CP Phase with Reactor Neutrinos

TL;DR

This paper explores how reactor neutrino experiments can detect the renormalization group effects on the leptonic Dirac CP phase by comparing the phase at different energy scales, using the upcoming TAO experiment.

Contribution

It introduces a novel method to probe RG running effects on the CP phase using reactor neutrino experiments, focusing on the mismatch in momentum transfer at production and detection.

Findings

Projected sensitivity to CP RG running beta function at TAO

Demonstrates the feasibility of detecting RG effects via phase deviation

Highlights the importance of momentum transfer differences in measurements

Abstract

We propose the possibility of using the near detector at reactor neutrino experiments to probe the renormalization group (RG) running effect on the leptonic Dirac CP phase $\delta_D$. Although the reactor neutrino oscillation cannot directly measure $\delta_D$, it can probe the deviation $\Delta \delta \equiv \delta_D(Q^2_d) - \delta_D(Q^2_p)$ caused by the RG running. Being a key element, the mismatched momentum transfers at neutrino production ($Q^2_p$) and detection ($Q^2_d$) processes can differ by two orders. We illustrate this concept with the upcoming Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) experiment and obtain the projected sensitivity to the CP RG running beta function $\beta_\delta$.