Measuring the Leptonic Dirac CP Phase with TNT2K

TL;DR

TNT2K combines a muon decay at rest source with T2HK to enhance measurement precision of the leptonic Dirac CP phase, offering advantages in efficiency, degeneracy avoidance, and robustness against new physics effects.

Contribution

It introduces a novel spectrum upgrade approach with a single muon decay at rest source to improve CP phase measurement, differing from flux, detector, or baseline upgrades.

Findings

Achieves better CP phase measurement with high efficiency.

Reduces CP uncertainty and degeneracy.

More cost-effective and technically simpler than alternative proposals.

Abstract

I describe how the TNT2K (Tokai and Toyama to Kamioka) configuration with a muon decay at rest ($\mu$DAR) add-on to T2(H)K can achieve better measurement of the leptonic Dirac CP phase $\delta_D$. It has five-fold advantages of high efficiency, smaller CP uncertainty, absence of degeneracy, as well as guaranteeing CP sensitivity against non-unitary mixing (NUM) and non-standard interaction (NSI). In comparison to the flux upgrade with T2K-II, the detector upgrade with T2HK, and the baseline upgrade with T2HKK, TNT2K is a totally different concept with spectrum upgrade to solve the intrinsic problems in current and next generations of CP measurement experiments. With a single $\mu$DAR source, TNT2K is much cheaper and technically much easier than the DAE$\delta$ALUS proposal. The latter needs three sources that cannot run simultaneously and consequently requires much higher fluxes. The single $\mu$DAR source at TNT2K also allows a single near detector ($\mu$Near) to fully utilize the neutrino flux for the purpose of constraining NUM, but this is impossible at DAE$\delta$ALUS with three spatially separated sources.