Non-Standard Interactions and Prospects for Studying Standard Parameter Degeneracies in DUNE and T2HKK

Abstract: The future long baseline experiments such as DUNE and T2HKK have promising prospects to determine the neutrino mass hierarchy and measuring standard $CP$ phase $\delta$. However, presence of possible non-standard interactions of neutrinos with matter may intricate this picture and is the subject matter of the present work. We have studied the standard parameter degeneracies in presence of non-standard interactions(NSI) with DUNE and T2HKK experiments. We examine the mass hierarchy degeneracy assuming (i) all NSI parameters to be non-zero and (ii) one NSI parameter($\epsilon_{e\mu}$) and its corresponding $CP$ phase($\delta_{e\mu}$) to be non-zero. We find that the later case is more appropriate to resolve mass hierarchy degeneracy with DUNE and T2HKK experiments due to relatively small uncertainties emanating from the NSI sector. We have, also, investigated the octant degeneracy with neutrino($\nu_{\mu}\rightarrow\nu_{e}$) and antineutrino($\bar{\nu}{\mu}\rightarrow\bar{\nu}{e}$) mode separately. We find that to resolve this degeneracy the long baseline experiment with combination of neutrino and antineutrino mode is essential. Furthermore, we have considered DUNE in conjunction with T2HKK experiment to study $CP$ phase degeneracy due to standard($\delta$) and non-standard($\delta_{e\mu}$) $CP$ phases. We find that DUNE and T2HKK, in conjunction, has more sensitivity for $CP$ violation effects(10$\sigma$ for true NH and 8.2$\sigma$ for true IH).