Experimental Study of Geoneutrinos with KamLAND
Experimental Study of Geoneutrinos with KamLAND
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KamLAND 中微子实验研究
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
S. Enomoto
中科院分区：
文献类型：
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作者：
S. Enomoto
神冈液体闪烁体反中微子探测器（KamLAND）由1000吨超纯液体闪烁体组成，周围环绕着1879个光倍增管（PMT），是第一个足够灵敏的探测器，可以探测到地球中微子。地球模型表明，KamLAND以238U衰变链的30个事件/1032个质子/年和232Th衰变链的8个事件/1032个质子/年的速率观测到地球中微子。探测器暴露时间为7.09×1031质子年，探测效率为0.687±0.007，“仅率”分析给出了$$25_{-18}^{+19}$$地中微子候选粒子。假设Th/U质量浓度比为3.9，“速率+形状”分析得出90% confidence interval for the total number of geoneutrinos detected to be from 4.5 to 54.2. This result is consistent with predictions from the Earth models. The 99% C.L. upper limit is set at 1.45×10−31 events per target proton per year, which is 3.8 times higher than the central value of the model prediction that gives 16 TW of radiogenic heat production from 238U and 232Th. Although the present data have limited statistical power, they provide by direct means an upper limit for the Earth’s radiogenic heat of U and Th.
The Kamioka liquid scintillator antineutrino detector (KamLAND), which consists of 1000 tones of ultra-pure liquid scintillator surrounded by 1879 photo-multiplier tubes (PMT), is the first detector sensitive enough to detect geoneutrinos. Earth models suggest that KamLAND observes geoneutrinos at a rate of 30 events/1032-protons/year from the 238U decay chain, and 8 events/1032-protons/year from the 232Th decay chain. With 7.09×1031 proton-years of detector exposure and detection efficiency of 0.687 ± 0.007, the ‘rate-only’ analysis gives $$25_{-18}^{+19}$$ geoneutrino candidates. Assuming a Th/U mass concentration ratio of 3.9, the ‘rate + shape’ analysis gives the 90% confidence interval for the total number of geoneutrinos detected to be from 4.5 to 54.2. This result is consistent with predictions from the Earth models. The 99% C.L. upper limit is set at 1.45×10−31 events per target proton per year, which is 3.8 times higher than the central value of the model prediction that gives 16 TW of radiogenic heat production from 238U and 232Th. Although the present data have limited statistical power, they provide by direct means an upper limit for the Earth’s radiogenic heat of U and Th.