2012/09/13 by Kaoru Hagiwara, Takayuki Kiwanami, Naotoshi Okamura +1 · 1 citation
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Baseline (sea) #Beam (structure) #CP violation #Detector #Neutrino #Neutrino Physics Research #Neutrino oscillation #Particle physics theoretical and experimental studies #Phase (matter) #Sensitivity (control systems) #hep-ph
paper · pdf · doi:10.1007/jhep06(2013)036
35 pages, 15 figures
arxiv created 2012/09/13 · openalex publication_date 2013/06/01 · arxiv updated 2015/06/11 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Oki Island is located between Japan and Korea along the Tokai-To-Kamioka (T2K) baseline. The distance from J-PARC to Oki Island is about 653km, which is twice that of the T2K experiment (L=295km). When the off-axis angle of the neutrino beam from J-PARC is 3.0^∘ (2.0^∘) at Super-Kamiokande (SK), the off-axis beam (OAB) with 1.4^∘ (0.6^∘) reaches at Oki Island. We examine physics case of placing a far detector in Oki Island during the T2K experimental period. We estimate the matter density profile along the Tokai-to-Oki baseline by using recent seismological measurements. For a detector of 100kton fiducial volume and 2.5x1021 POT (protons on target) exposure for both νμand νμbeams, we find that the mass hierarchy pattern can be distinguished at 3σlevel if sin22thetarct ≡ 4|Ue3|2(1-|Ue3|2) \gsim 0.09, by observing the electron-like CCQE (Charged-Current Quasi Elastic) events. The CP phase in the Maki-Nakagawa-Sakata lepton flavor mixing matrix, δmns, can be constrained with ± 20^∘. As a reference, we repeat the same analysis by placing the same detector in Korea at L=1000km and OAB=0.5^∘ (T2KK) and also by placing it at the SK site (T2K122). The Tokai-to-Kamioka-OKI (T2KO) sensitivity to the mass hierarchy is about 1/3 (in Δχ2min) of T2KK, while the sensitivity to the phase δmns is similar between T2KO and T2KK. The T2K122 option has almost no sensitivity to the mass hierarchy, and cannot measure the CP phase except when δmns ∼ -90^∘ (90^∘) for the normal (inverted) hierarchy.