世界トップレベル研究拠点プログラム(WPIプログラム) 平 …ギー、暗黒物質、ニュートリノ、統一理論(超弦理論や量子重力)を主たる研究
ニュートリノ研究会 @ 宇宙線研 2013.03.15
-
Upload
yoshitaro-takaesu -
Category
Science
-
view
140 -
download
2
Transcript of ニュートリノ研究会 @ 宇宙線研 2013.03.15
![Page 1: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/1.jpg)
Determination of mass hierarchy with reactor neutrino experiment
Yoshitaro Takaesu
KIAS/KNRC
In collaboration with S.F. Ge, N. Okamura and K. Hagiwara
arXiv: 1210.8141
![Page 2: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/2.jpg)
Introduction
is observed.
Reactor Experimentscan determine the Neutrino Mass Hierarchy .
The sensitivity is studiedof future Medium Baseline Reactor Experimentsfor determining the Neutrino Mass Hierarchy
![Page 3: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/3.jpg)
PMT
Reactor neutrino experiment
Reactor Detector
Inside Detector
Inverse Beta Decay (IBD)
![Page 4: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/4.jpg)
Energy Distribution
@ Detector
near far
![Page 5: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/5.jpg)
How to distinguish Mass Hierarchy ?
Mass Hierarchy difference
Max:
vanish:
![Page 6: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/6.jpg)
MH difference in spectrum
![Page 7: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/7.jpg)
Advantages of Reactor Experiment
• Can determine MH independently from CP phase and matter effects.
•Need only smaller detector than other experiments (e.g., LBL, atmospheric).
•Free neutrino source with adjustable baseline length
![Page 8: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/8.jpg)
Analysis methods for MH determination
• Fourier analysis
• analysis
hep-ph/0612022 J.G. Learned et al. arXiv: 0807.3203 L. Zhan et al.arXiv: 0901.2976 L. Zhan et al.arXiv: 1208.1551 X. Qian et al.arXiv: 1208.1991 E. Ciuffoli et al.
hep-ph/030601 S. Choubey et.al.arXiv: 0810.2580 M. Batygov et.al.arXiv: 1011.1646 P. Ghoshal et.al.
![Page 9: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/9.jpg)
Fourier Analysis
• has sensitivity for small . • Don’t need accurate knowledge of or flux.
![Page 10: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/10.jpg)
analysis
Data is fitted with the theoretical prediction ,assuming NH or IH.
Fitting parameters are
Penalty term
![Page 11: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/11.jpg)
analysis – MH determination
MH is determined as the hierarchy which gives smaller . Ex)
MH is NH.
Sensitivity is estimated by
We claim that MH is determined with significane.
acc. MHrej. MH
![Page 12: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/12.jpg)
Sensitivity for MH determination
36 km (Max MH diff.)
Max Sensitivity
Typical sensitivity curve as a function of Baseline length L
![Page 13: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/13.jpg)
Effect of
Baseline Length L should be long enough.
L = 30km
L = 50km
![Page 14: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/14.jpg)
Pull Factor
![Page 15: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/15.jpg)
Effect of Energy Resolution
a = 0 a = 6%
Evergy Resolution affects the sensitivity significantly.
How good should the energy resolution be ?
3% ? Not enough for RENO50 class of detector (5kton).
![Page 16: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/16.jpg)
Sensitivity for MH determination
20GW 5kton 5yrs
Current ResolutionNH
Optimal L ~ 50 km
![Page 17: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/17.jpg)
Systematic part of Resolution
20GW 5kton 5yrs
Current Resolution • Sensitivity is reduced by 40%.
• Optimal L is shortened by a few km.
b = 0 b = 1%
a = 2%
a = 3%
![Page 18: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/18.jpg)
Parameter measurement @ L ~ 50 km
Parameter measurement is not sensitive to the Energy Resolution.
~ 0.5% accuracycan be measured accurately @ L ~ 50 km
L = 50km
1%
1%
1%
![Page 19: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/19.jpg)
Fluctuation of Sensitivity
So far, we have discussed on the sensitivity using the “typical data set”.
In the real experiments, event number in each bin, ,fluctuates from the “typical event number”, .
Then, follows Gaussian distribution. a = 3%
a = 2%
0 4 13
20GW 5kton 5yrs
2% level of energy resolution is desired.
![Page 20: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/20.jpg)
Expected Probability
L = 50 km
![Page 21: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/21.jpg)
How to achieve 2% energy resolution ?
Increase the photo-electron (p.e.)detected by PMT.
p.e.~ 200 pe/MeV ~ 2000 pe/MeV
Ex)
• Increase PMT coverage
• Increase QE of PMT
• More transparent LS
![Page 22: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/22.jpg)
By Channgen Yang @ NuMass 2013
![Page 23: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/23.jpg)
Multi-reactor interference
Baseline difference should be < 500m.
0 m
500 m
1 km
1.5 km
2 km
arXiv: 1302.0624
L1 L2
L1
|L1 – L2|
![Page 24: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/24.jpg)
Multi-reactor interference
Because of this effect, DayaBayII has changed its location.
![Page 25: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/25.jpg)
Multi-reactor interference
RENO
50 km
200 km
RENO
1.3 km
RENO50
The angle to RENO50 may affect the sensitivity.
Reactor site
![Page 26: ニュートリノ研究会 @ 宇宙線研 2013.03.15](https://reader031.fdocuments.net/reader031/viewer/2022020213/58eeb0401a28ab214b8b459d/html5/thumbnails/26.jpg)
Summary
We have discussed the sensitivity of Medium Baseline Reactor Experiments for MH determination.
For 20GW 5kton 5yrs exposure,
50km optimal Baseline Length
a < 3%
b < 1%
0.5% accuracy is achieved for
of Energy Resolution is required.