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博士論文発表会 2015 Xu Benda

『Observation of Geoneutrinos at KamLAND during Reactor Shutdown 』
(原子炉停止期間におけるカムランドでの地球ニュートリノ観測)

 

博士課程3年 XU Benda
KamLAND所属

DSCN1975発表:2014年7月22日

 

概要:
After the great Tohoku earthquake in 2011, all the nuclear power plants in Japan are shut- down for safety inspection. This reactor-off period offers a unique opportunity to study the geoneutrinos from the Earth.

This work adds a new reactor-off dataset from Dec., 2012 to Jan., 2014 to the most recent KamLAND result. Since KamLAND first data from 2002, the total live time is accumu- lated up to 9.14 years. With the target proton of about 5.979 × 1031, the total exposure is 5.46 × 1032 proton year.

Assuming Th/U mass ratio of 3.9, the geoneutrino flux from 238U and 232Th is found to be 27.2 ± 8.9 TNU, or (3.1 ± 1.0) × 106cm−2s−1. The geoneutrino detection significance is 5.05σ, thanks to the low background from reactor ν ̄e.

Radiogenic heat from the mantle is found to be 0-10.5TW, and Urey ratio to be 0-0.35. The deficit of energy sources to surface heat loss of the Earth becomes larger.

This result is consistent with the assumption of no U or Th in the mantle, and in favor of cosmochemical models which relates bulk silicate earth with enstitate chondrites. The geody- namical models which implies more mantle radiogenic heat, are excluded at 93.4% confidence level.

 

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