Re-evaluation of the T2KK physics potential with simulations including backgrounds
Re-evaluation of the T2KK physics potential with simulations including backgrounds
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DOI：
10.1088/1126-6708/2009/07/031
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发表时间：
2009-01
影响因子：
5.4
通讯作者：
K. Hagiwara;N. Okamura
中科院分区：
文献类型：
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作者：
K. Hagiwara;N. Okamura
正在检查的东海到神冈和韩国 (T2KK) 中微子振荡实验可以具有很高的灵敏度，可以确定超级神冈 (SK) 相对较大 (~ 3.0°) 离轴角光束和韩国 L~1,000 km 处较小 (~ 0.5°) 离轴角光束组合的中微子质量等级。我们通过考虑由于电子或 μ 子能量的有限分辨率、核费米运动和共振产生而导致的重建中微子能量的拖尾，以及 νμ → νe 振荡信号的中性电流 π0 产生背景来阐述以前的研究。结果发现，如果在韩国放置 100 kton 水切伦科夫探测器，则在 5 × 1021} POT（目标上的质子）曝光或 T2K 实验 5 年的层次结构正常（倒置）时，如果 sin22θRCT ≠ 4|Ue3|2(1 − |Ue3|2) 0.08(0.09)，仍然可以在 3σ 水平确定质量层次模式。 π0背景降低了质量等级确定的能力，而来自CC核共振产物的事件对等级辨别能力有积极贡献。我们还发现π0背景严重影响CP相位测量。尽管在 sin22θRCT 0.04 的情况下，对于具有上述暴露的正常（反向）层次结构，在 1σ 水平上 δMNS 的精度仍然可以受到 ~ ±45° (±60°) 的约束，但即使对于 δMNS = ±90° 和 sin22θRCT = 0.1，也不能再在 3σ 水平上建立 CP 违规。需要大约四倍的曝光量才能以 ±30° 的精度测量 δMNS。
The Tokai-to-Kamioka-and-Korea (T2KK) neutrino oscillation experiment under examination can have a high sensitivity to determine the neutrino mass hierarchy for a combination of relatively large ( ~ 3.0°) off-axis angle beam at Super-Kamiokande (SK) and small ( ~ 0.5°) off-axis angle at L ~ 1,000 km in Korea. We elaborate previous studies by taking into account smearing of reconstructed neutrino energy due to finite resolution of electron or muon energies, nuclear Fermi motion and resonance production, as well as the neutral current π0 production background to the νμ → νe oscillation signal. It is found that the mass hierarchy pattern can still be determined at 3σ level if sin22θRCT ≡ 4|Ue3|2(1 − |Ue3|2) 0.08(0.09) when the hierarchy is normal (inverted) with 5 × 1021} POT (protons on target) exposure, or 5 years of the T2K experiment, if a 100 kton water Cerenkov detector is placed in Korea. The π0 backgrounds deteriorate the capability of the mass hierarchy determination, whereas the events from CC nuclear resonance productions contribute positively to the hierarchy discrimination power. We also find that the π0 backgrounds seriously affect the CP phase measurement. Although δMNS can still be constrained with an accuracy of ~ ±45° (±60°) at 1σ level for the normal (inverted) hierarchy with the above exposure if sin22θRCT 0.04, CP violation can no longer be established at 3σ level even for δMNS = ±90° and sin22θRCT = 0.1. About four times higher exposure will be needed to measure δMNS with ±30° accuracy.