Proposal for an Extended Run of T2K to $20\times10^{21}$ POT

TL;DR

This paper proposes extending the T2K neutrino experiment to increase data collection, aiming to observe CP violation with high significance and improve measurements of key neutrino mixing parameters before next-generation experiments begin.

Contribution

It introduces a plan to extend T2K's data-taking to $20\times 10^{21}$ POT, enabling early CP violation observation and more precise parameter measurements.

Findings

Potential observation of CP violation at 3$\sigma$ significance

Measurement of $\theta_{23}$ with 1.7$^\circ$ precision

Measurement of $\Delta m^2_{32}$ with 1% accuracy

Abstract

Recent measurements by the T2K neutrino oscillation experiment indicate that CP violation in neutrino mixing may be observed in the future by long-baseline neutrino oscillation experiments. We propose an extension to the currently approved T2K running from $7.8\times 10^{21}~\mbox{POT}$ to $20\times 10^{21}~\mbox{POT}$, aiming at initial observation of CP violation with 3$\,\sigma$ or higher significance for the case of maximum CP violation. The program also contains a measurement of mixing parameters, $\theta_{23}$ and $\Delta m^2_{32}$, with a precision of 1.7$^\circ$ or better and 1%, respectively. With accelerator and beamline upgrades, as well as analysis improvements, this program would occur before the next generation of long-baseline neutrino oscillation experiments that are expected to start operation in 2026.