Sensitivity of the T2HKK experiment to the non-standard interaction

TL;DR

This paper evaluates the T2HKK experiment's ability to detect non-standard neutrino interactions, showing that certain configurations can significantly constrain NSI parameters and outperform other experiments in measuring CP phases.

Contribution

It provides the first detailed sensitivity analysis of T2HKK to flavor-dependent NSI, highlighting optimal off-axis angles and comparing its performance with DUNE and atmospheric experiments.

Findings

The 1.3° off-axis configuration offers the highest sensitivity to NSI parameters.

T2HKK can exclude NSI for ||  1 or ||  0.2 at 3.

T2HKK shows superior sensitivity to CP phases compared to DUNE in the presence of NSI.

Abstract

If the flavor dependent non-standard interactions (NSI) in neutrino propagation exist, then the matter effect is modified and the modification is parametrized by the dimensionless parameter $\epsilon_{\alpha\beta}~(\alpha,\beta=e, \mu, \tau)$. In this paper we discuss the sensitivity of the T2HKK experiment, whose possibility is now seriously discussed as a future extension of the T2K experiment, to such NSI. On the assumption that $\epsilon_{\alpha\mu}=0~(\alpha=e, \mu\tau)$ and $\epsilon_{\tau\tau}=|\epsilon_{e\tau}|/(1+\epsilon_{ee})$, which are satisfied by other experiments to a good approximation, we find that, among the possible off-axis flux configurations of $1.3^\circ$, $1.5^\circ$, $2.0^\circ$ and $2.5^\circ$, the case of the off-axis angle $1.3^\circ$ gives the highest sensitivity to $\epsilon_{ee}$ and $|\epsilon_{e\tau}|$. Our results show that the $1.3^\circ$ off-axis configuration can exclude NSI for $|\epsilon_{ee}|\gtrsim 1$ or $|\epsilon_{e\tau}|\gtrsim 0.2$ at 3$\sigma$. We also find that in the presence of NSI, T2HKK (for the off-axis angle $1.3^\circ$) has better sensitivity to the two CP phases ($\delta_{CP}$ and arg($\epsilon_{e \tau}$)) than DUNE. This is because of the synergy between the two detectors i.e., one at Kamioka and one at Korea. T2HKK has better sensitivity to the CP phases than the atmospheric neutrino experiment at Hyperkamiokande in inverted hierarchy, but in normal hierarchy the atmospheric neutrino experiment has the best sensitivity to the CP phases.