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Determina)on of mass hierarchy with reactor neutrino experiment
Yoshitaro Takaesu KIAS/KNRC
In collabora)on with S.F. Ge, N. Okamura and K. Hagiwara
Introduc)on
is observed at Short Baselin Rector Experiments.
Reactor neutrino Experiments may be able to determine the Neutrino Mass Hierarchy .
The sensi;vity is studied of future Reactor neutrino Experiments for determining the Neutrino Mass Hierarchy
sin2 2�13 � 0.1
Reactor neutrino experiment
�e + p� e+ + n
�e
@ Reactor @ Detector �e�e
=
Baseline (L km)
Pee
�
MH difference in Pee
Mass Hierarchy difference
By N. Okamura
Energy Distribu)on @ Detector
10000 20000 30000 40000
30 km NH IH
2000 6000
10000 14000 40 km NH
IH
1000 3000 5000 7000
dN /
dEi [
1/M
eV]
50 km NH IH
0 1000 2000 3000 4000
2 3 4 5 6 7 8
Ei [MeV]
60 km NH IH
L = 30km
L = 40km
L = 50km
L = 60km
�e
Es)ma)on of the sensi)vity for MH
�2 fit
103
104
2 3 4 5 6 7 8
dN / d
E i [1/Me
V]
Ei [MeV]
50km
Data
( )
or NH IH
Sensi)vity: (��2)min = �2min(wrong MH)� �2
min(true MH)
Sensi)vity for Mass Hierarchy
0
2
4
6
8
10
12
14
10 20 30 40 50 60 70 80 90 100
(6r
2 ) min
L [km]
b = 0
a = 2% NH IH
3% NH IH
4% NH IH
5% NH IH
6% NH IH
20GW 5kton 5yrs
Effect of Energy Resolu)on
b: systematic error parta: statistical error part
w/o Resolu)on
Evergy Resolu)on effect is
Problema)c.
�EE
=
��a�E
�2
+ b2
a = 6% �E �= 0
Effect of Baseline Length L
Baseline Length L should be long enough.
MH difference remains.
|�m231|+�
|�m231|
L = 30km
MH difference can disappear when is shiUed.
|�m231|+�
|�m231|
|�m231|
L = 50km
|�m231|
Sensi)vity for Mass Hierarchy
0
2
4
6
8
10
12
14
10 20 30 40 50 60 70 80 90 100
(6r
2 ) min
L [km]
b = 0
a = 2% NH IH
3% NH IH
4% NH IH
5% NH IH
6% NH IH
20GW 5kton 5yrs
opVmal Baseline L ~ 50km
a < 3% is required for
. (��2)min � 9
�EE
=
��a�E
�2
+ b2
Systema)c Error of Resolu)on
0
2
4
6
8
10
12
14
10 20 30 40 50 60 70 80 90 100
(6r
2 ) min
L [km]
(a, b) = (2, 0) NH IH
(2, 0.5) NH IH
(2, 0.75) NH IH
(2, 1) NH IH
b opVmal L
b < 1% is required for
. (��2)min � 9
20GW 5kton 5yrs
�EE
=
��a�E
�2
+ b2
Summary
We have studied the sensi;vity of Medium Baseline Reactor Experiments for MH determina;on.
For 20GW 5kton 5yrs exposure,
50km opVmal Baseline Length
a < 3% b < 1%
for determinaVon of MH with Reactor neutrino.
of is required �E
E=
��a�E
�2
+ b2
Expected Sensi)vity
10-7
10-6
10-5
10-4
10-3
0.01
0.1
1
0 1 2 3 4 5 6 7 8 9 10 11
1 - P
1m
2m
3m
4m
5m
×1
×4
×9
×1
×4
×9
×16
×25
No FluctuationFluctuation
(a, b) = (2, 0.5) (3, 0.75)
�(��2)min
20GW 5kton 5yrs �n
Parameter measurement
0.51.01.52.0
sin22e12
×10-2(a, b) = (3, 0.5) NH
IH(3, 1) NH
IH(6, 1) NH
IH
1234 sin22e13
×10-3
0.51.01.5
Stat
istic
al U
ncer
tain
ty
6m221
×10-6eV2
0246
10 20 30 40 50 60 70 80 90 100
L [km]
|6m231|
×10-5eV2
Fi_ed parameter values are not sensi;ve to the Energy Resolu;on
~ 0.5% accuracy can be achieved for sin2 2�12,�m221,�m2
31
Mass Hierarchy
Which Hierarcy is realized in Nature?
m1
m2
m3
Normal Hierarchy (NH)
m3
m1
m2
Inverted Hierarchy (IH)
�m221
|�m231|
� 2.3� 10�3eV2
� 7.5� 10�5eV2
�m221
|�m231|
m�