Probing unitarity violation of lepton flavor mixing matrix with reactor antineutrinos at JUNO and TAO

TL;DR

This paper explores how reactor antineutrino experiments at JUNO and TAO can test for violations of the unitarity of the lepton flavor mixing matrix by analyzing event rates sensitive to such violations.

Contribution

It introduces a self-consistent approach to analyze neutrino production, detection, and propagation for probing unitarity violation using reactor antineutrino data.

Findings

Event rates depend on unitarity violation parameters.

JUNO and TAO can independently constrain unitarity violation.

Analysis emphasizes the importance of production and detection effects.

Abstract

Motivated by the precise measurements of neutrino oscillation parameters at Jiangmen Underground Neutrino Observatory (JUNO), we investigate the possibility of probing the unitarity violation of lepton flavor mixing matrix solely with reactor antineutrinos. First, we stress that it is necessary to reconsider the production and detection of neutrinos in a self-consistent way, apart from neutrino propagation, when analyzing experimental sensitivities to unitarity violation. Then, concentrating on JUNO and its satellite experiment Taishan Antineutrino Observatory (TAO), we demonstrate how the event rates of inverse beta decays (i.e., $\overline{\nu}^{}_e + p \to e^+ + n$) for observing $\overline{\nu}^{}_e \to \overline{\nu}^{}_e$ oscillations, and those of elastic antineutrino-electron scattering (i.e., $\overline{\nu}^{}_\alpha + e^- \to \overline{\nu}^{}_\alpha + e^-$ with $\alpha = e, \mu, \tau$) for $\overline{\nu}^{}_e \to \overline{\nu}^{}_\mu$ and $\overline{\nu}^{}_e \to \overline{\nu}^{}_\tau$ oscillations, depend on the parameters characterizing unitarity violation. Our investigation will be useful for JUNO and TAO to place independent constraints with more data in the near future.