JUNO as a Probe of the Pseudo-Dirac Nature using Solar Neutrinos

It remains a possibility that neutrinos are pseudo-Dirac states, such that a generation is composed of two maximally mixed Majorana neutrinos separated by a very small mass difference. We explore the physics potential of the JUNO experiment in constraining this possibility using the measurement of solar neutrinos. In particular, we investigate cases where one or three sterile states are present in addition to the active states. We consider two scenarios: one where JUNO's energy threshold allows for the measurement of $pp$ solar neutrinos, and the case where JUNO can only measure $^7$Be neutrinos and above. We find that JUNO will be able to constrain pseudo-Dirac mass splittings of $\delta m^2 \gtrsim 2.9\times 10^{-13}~{\rm eV^2}$ for the scenario including $pp$ solar neutrinos, and $\delta m^2 \gtrsim 1.9\times 10^{-12}~{\rm eV^2}$ when the measurement only considers $^7$Be monochromatic neutrinos, at the $3\sigma$ C.L. Thus, including $pp$ neutrinos will be crucial for JUNO to improve current constraints on the pseudo-Dirac scenario from solar neutrinos.