Yoshitaro Takaesu U. of Tokyo Determination of mass hierarchy with medium baseline reactor neutrino experiments.
Yoshitaro TakaesuU. of Tokyo
Determination of mass hierarchy with medium baseline reactor neutrino
experiments.
Reactor neutrino experiment
νe
Detector
Reactors
6 × 1023 νe/ 3GW/ 15min
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PMT
Inside Detector (Inverse Beta Decay)
Reactor neutrino experiment
νe
Detector
Reactors
6 × 1023 νe/ 3GW/ 15min
3
Topics on medium baseline reactor ex.
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• Optimum baselines
• Energy resolution (Energy scale uncertainty)
• Multiple reactor effects
• Geo neutrino
• Synergy with Long Baseline experiments
• Statistical test of hypothesis
• Fourier analysis vs. chi^2 analysis
• Nuclear recoil effect
etc…
survival prob. (Pee)
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L ~ 1km
MH independent current reactor experiment
[DayaBay: Neutrino2014]
MH
[Minakata,Nunokawa,Parke,Funchal: hep-ph/0701151]
Sensitivity to the Mass hierarchy
The typical sensitivity curve of this experiment
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chi^2 analysisWe define
Naively, the significance of this rejection is , but…(∆ χ2)min σ
NHIH
Not appropreate for the MH determination
c.f.) Qian et.al. arXiv: 1210.3651
Evslin et.al. arXiv: 1305.5150
NH is true: tends to be Positive.
IH is true: tends to be Negative.
IH is rejectedNH is rejected
NH is true case
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Energy Resolution
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Effect of Energy resolution
16.5GW 18kton 5yrs (RENO-50)Current value
NH
δE
E=
a
E / MeV
2
+ b2
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[Ge,Hagiwara,Okamura,Takaesu: 1210.8141]
How to achieve better Energy Resolution?
Increase the photo-electron (p.e.)detected by PMT.
p.e.~ 200 pe/MeV ~ 1000 pe/MeV
Ex)
• Increase PMT coverage
• Increase QE of PMT
• More transparent LS•More Light yield
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~ 6% ~ 3%
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[L.Wen: Neutrino 2014]
Multiple Reactor Effect
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E. Ciuffoli, J. Evslin, X. Zhang: 1302.0624Y-F. Li, J. Cao, Y. Wang, L. Zhan: 1303.6733
ΔL = L1 – L2
Reactor1
Multiple Reactor Effect
L1 L2
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Reactor1 + Reactor2
multi-cores
Multiple Reactor Effect: RENO-50 case 16.5GW
18kton 5yrs
a = 3%, b = 0.5%δE
E=
a√
E
2
+ b2
(∆ χ2)min
All Reactors50 km
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250m
[Y.Takaesu: Internationalworkshop on RENO-50]
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[L.Wen: Neutrino 2014]
Geo-neutrino BG
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KamLAND: 38.3 +- 10 TNU [1/(10^32 proton*yrs)]
Borexino: 38.8 +- 12 TNU
[Gando et.al 2011, Nature Geosci.]
[Ranucci: Neutorino 2014]
36 GW, 20 kton, 5 years, Eres=3% (JUNO)
arXiv:1006.1113
SummaryFuture Reactor neutrino Experiment for MH determination
50km is the optimum baseline length
For > 3-sigma determination within 5 years (15GW 20kton)
3% of Energy resolution is required.
(Energy Scale uncertainty should be controlled carefully
arxiv:0901.2976, 1208.1551, 1308.0591)
Multiple reactor effect significantly affects the sensitivity.
Geo-neutrino may also become concern.
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