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

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 $δ_D$. Although the reactor neutrino oscillation cannot directly measure $δ_D$, it can probe the deviation $Δδ\equiv δ_D(Q^2_d) - δ_D(Q^2_p)$ 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 $β_δ$.