T2K基线上Oki岛中微子振荡远探测器实验的物理势
Physics potential of neutrino oscillation experiment with a far detector in Oki Island along the T2K baseline
摘要：
隐岐岛位于日本和韩国之间的东海到神冈（T2 K）基线。从J-PARC到隐岐岛的距离约为653公里，是T2 K实验（L= 295公里）的两倍。当来自J-PARC的中微子束的离轴角为3.0^ \circ（2.0^ \circ）时，在超级神冈（SK），离轴束（OAB）与1.4^ \circ（0.6^ \circ）到达隐岐岛。我们研究在T2 K实验期间在隐岐岛放置远探测器的物理情况。我们估计的物质密度分布沿东海到隐岐基线使用最近的地震测量。对于基准体积为100 kton，辐照量为2.5 × 10 ~（21）POT（质子在靶上）的探测器，我们发现，如果sin ^22 θ_rct \equiv 4，则质量分级模式可以在3σ水平上区分|U_{e3}| ^2（1-|U_{e3}| ^2）\gsim 0.09，通过观察类电子CCQE（Charged-Current Quasi Elastic）事件。Maki-Nakagawa-Sakata轻子味混合矩阵δ_mns中的CP相可以用\pm 20^ \circ来约束。作为参考，我们通过在韩国L= 1000 km和OAB=0.5^ \circ（T2 KK）放置相同的探测器以及将其放置在SK站点（T2 K_122）重复相同的分析。东海-神冈-OKI（T2 KO）对质量等级的灵敏度约为T2 KK的1/3（以Δ x^2_min计），而对相位δ_mns的灵敏度在T2 KO和T2 KK之间相似。T2K_122选项对质量等级几乎没有敏感性，并且不能测量CP相位，除非正常（倒置）等级的δ_mns \sim-90 ^\circ（90^ \circ）。
英文摘要：
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^\circ (2.0^\circ) at Super-Kamiokande (SK), the off-axis beam (OAB) with 1.4^\circ (0.6^\circ) 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 2.5x10^21 POT (protons on target) exposure for both ν_μand \barν_μbeams, we find that the mass hierarchy pattern can be distinguished at 3σlevel if sin^22theta_rct \equiv 4|U_{e3}|^2(1-|U_{e3}|^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, δ_mns, can be constrained with \pm 20^\circ. As a reference, we repeat the same analysis by placing the same detector in Korea at L=1000km and OAB=0.5^\circ (T2KK) and also by placing it at the SK site (T2K_122). The Tokai-to-Kamioka-OKI (T2KO) sensitivity to the mass hierarchy is about 1/3 (in Δχ^2_min) of T2KK, while the sensitivity to the phase δ_mns is similar between T2KO and T2KK. The T2K_122 option has almost no sensitivity to the mass hierarchy, and cannot measure the CP phase except when δ_mns \sim -90^\circ (90^\circ) for the normal (inverted) hierarchy.
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