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Yoshitaro Takaesu KIAS/KNRC
The Sensi7vity to Mass Hierarchy determina7on of Future Reactor
Neutrino experiments
In collabora7on with S.F. Ge, N. Okamura and K. Hagiwara JHEP 1305:131,2013
Introduc7on
2
Mass Hierarchy
3
P (�e � �e) =
�����
3�
i=1
Uei exp��i
m2i
2Ei
�U�
ei
�����
2
= P (�e � �e)
�m231 = m2
3 �m21 > 0 �m2
31 = m23 �m2
1 < 0
�m231 < 0
�m231 > 0
�e
Reactor neutrino experiment Detector
Baseline Length L
Reactors
6� 1023 �e/3GW/15min
Evis
� (E� � 0.8)MeV
PMT
��
�
�
Inside Detector (Inverse Beta Decay)
E� < 10MeV
MH difference in spectrum �e
Sensi7vity
analysis
The theore2cal predic2on is fi7ed to the Data, assuming NH or IH.
�2min(NH) �2
min(IH)
Nfiti =
�dEvis
NpT
4�L2
� �
Ethr
dE� �(E�)Pee �IBD G(E� , Evis)
FiAng parameters are �12, �13, �m221, |�m2
31|, fsys
Penalty term
Nfiti
�2
0
5
10
15
20
25
30
35
40
10 20 30 40 50 60 70 80 90 100
(6r2 ) m
in
L [km]
a = 2% NH3% NH4% NH5% NH6% NH
Sensi7vity to the Mass hierarchy
16.5GW 18kton 5yrs Current value
NH a � 7%
b = 0
b � 1%
�EE
=
�����
a�E/MeV
�2
+ b2
Effect of b term �EE
=
��a�E
�2
+ b2
16.5GW 18kton 5yrs
20 30 40 50 60 70 80 90 100L [km]
b = 0%0.5%
0.75%1%
a = 3% a = 2%
0
5
10
15
20
25
30
35
40
10 20 30 40 50 60 70 80 90
(6r2 ) m
in
L [km]
b = 0% b = 1% Sensi7vity 40%
Imrovement of b term is also important
0
5
10
15
20
25
30
35
40
10 20 30 40 50 60 70 80 90 100
(6r2 ) m
in
L [km]
a = 2% NH3% NH4% NH5% NH6% NH
Sensi7vity to the Mass hierarchy
16.5GW 18kton 5yrs Current value
NH a � 7%
�(�m231) Small Flux
b = 0
b � 1%
�EE
=
�����
a�E/MeV
�2
+ b2
Interference Effect
Mul7-‐reactor interference
L1 L2
E. Ciuffoli, J. Evslin, X. Zhang: 1302.0624 Y-‐F. Li, J. Cao, Y. Wang, L. Zhan: 1303.6733
ΔL = L1 – L2
RENO Reactor mul7-‐cores
Mul7-‐reactor interference 16.5GW 18kton 5yrs a = 3%, b = 0.5%
�EE
=
��a�E
�2
+ b2
RENO Reactor
01234567891011
(��2)min
All Reactors
Summary Future Reactor neutrino Experiment for MH determina2on
with 16.5GW 18kton Reactor complex,
a < 3% b < 0.5%
of Energy Resolu7on is required for > 3-‐sigma determina2on within 5 years.
�EE
=
��a�E
�2
+ b2
Interference among reactor cores significantly affects the sensi2vity.
Many Efforts for MH determina2on have started !
Backup Slides
15
Energy Distribu7on �e
@ Detector �e
near
dNfar
dEvis=
NpT
4�L2
� �
Ethr
dE� �(E� )Pee �IBD G(E� , Evis)
Pee
far
L
Fourier Analysis
FCT(�m2) =�
d
�L
E
�dN
dEvis
�L
E
�cos
��m2 L
E
�
FST(�m2) =�
d
�L
E
�dN
dEvis
�L
E
�sin
��m2 L
E
�
• has sensi2vity for small . • Don’t need accurate knowledge of or flux.
sin2 2�13 � 0.005|�m2
31(32)| �e
Effects of to the sensi7vity
|�m231|
L = 30km
�|�m231|
|�m231|
L = 50km
Baseline should be long enough
|�m231|+��2 fit
�2 fit |�m231|+�
Effect of Energy Resolu7on Evergy Resolu7on affects the sensi7vity significantly.
�E
E=
a�E
Pull Factors of fidng parameters
-0.25 0
0.25 0.5 sin22e12
2% NH IH
3% NH IH
6% NH IH
-0.25 0
0.25 0.5 sin22e13
-0.25 0
0.25 0.5
pull
fact
or
6m221
-0.25 0
0.25 0.5
|6m231|
-0.25 0
0.25 0.5
10 20 30 40 50 60 70 80 90 100L [km]
fsys
Interpreta7on of (��2)min
Dashed: �
(��2)min
Solid: 1� p
There are studies based on Bayesian approach.
This is a frequen2st approach to interpret . (��2)min
Qian et.al. arXiv: 1210.3651 Evslin et.al. arXiv: 1305.5150
2� � (1� p) � 95.5%1� � (1� p) � 68.2%
3� � (1� p) � 99.7%...
Reactor neutrino experiment (contd.)
22
Energy Resolusion Energy Scale Unc. ~ 2%
Reconstructed E�
Energy Resolu7on
�E
E=
�����
4.6%�E/MeV
�2
+ (0%)2
�E
E=
�����
3.6%�E/MeV
�2
+ (0.6%)2
�E
E=
�����
4.6%�E/MeV
�2
+ (0%)2
J.S. Park, S.B. Kim (RENO50)
Energy scale uncertainty Energy scale uncertainty is controlled to ~ 2% for current detectors.
J. Evslin et.al. arXiv: 1308.0591
No E scale Unc. Unknown E scale (worst case)
Effect of Energy scale Uncertainty
