talk at neutrino conference, kyoto
TRANSCRIPT
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
2
PMT
Inside Detector (Inverse Beta Decay)
Reactor neutrino experiment
νe
Detector
Reactors
6 × 1023 νe/ 3GW/ 15min
3
Topics on medium baseline reactor ex.
4
• 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)
5
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
6
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
7
Energy Resolution
8
Effect of Energy resolution
16.5GW 18kton 5yrs (RENO-50)Current value
NH
δE
E=
a
E / MeV
2
+ b2
9
[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
10
~ 6% ~ 3%
11
[L.Wen: Neutrino 2014]
Multiple Reactor Effect
12
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
13
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
14
250m
[Y.Takaesu: Internationalworkshop on RENO-50]
15
[L.Wen: Neutrino 2014]
Geo-neutrino BG
16
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.
17