Testing NSI suggested by the solar neutrino tension in T2HKK and DUNE

It was shown that the tension between the mass-squared differences obtained from solar neutrinos and those acquired through KamLAND experiments may be solved by the introduction of a non-standard flavor-dependent interaction (NSI) in neutrino propagation. In this study, we discuss the possibility of testing such a hypothesis using the future long-baseline neutrino experiments T2HKK and DUNE. Assuming that the NSI does not exist, we provide the excluded region within the ($epsilon_D$, $epsilon_N$) plane, where $epsilon_D$ and $epsilon_N$ are the parameters appearing in the solar neutrino analysis conducted with the NSI. We find that the best-fit value from the solar neutrino and KamLAND data (global analysis of a particular coupling to quarks) can be tested at more than 10$sigma$ (3$sigma$) by these two experiments for most of the parameter space.