Terrestrial matter effects on reactor antineutrino oscillations at JUNO or RENO-50: How small is small?

Abstract

We have carefully examined, in both analytical and numerical ways, how small the terrestrial matter effects can be in a given medium-baseline reactor antineutrino oscillation experiment like JUNO or RENO-50. Taking the forthcoming JUNO experiment as an example, we show that the inclusion of terrestrial matter effects may reduce the sensitivity of the neutrino mass ordering measurement by Δ 2MO≃ 0:6, and a neglect of such effects may shift the best-fit values of the avor mixing angle θ12 and the neutrino mass-squared di-erence θ21 by about 1αto 2α in the future data analysis. In addition, a preliminary estimate indicates that a 2α sensitivity of establishing the terrestrial matter effects can be achieved for about 10 years of data taking at JUNO with the help of a suitable near detector implementation.