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Introduc)on
is observed
Reactor Experiments (Medium Baseline) will determine the Neutrino Mass Hierarchy .
We study the sensi:vity of such future Experiments.
sin2 2�13 � 0.1
RENO
DayaBay
Neutrino Mass Hierarchy
m1
m2
m3
Normal Hierarchy (NH)
m3
m1
m2
Inverted Hierarchy (IH)
�m221
|�m231|
� 2.3� 10�3eV2
� 7.5� 10�5eV2
�m221
|�m231|
Which Hierarcy is realized in Nature?
m�
Oscilla)on
Mass Hierarchy difference
�e � �e
How to dis)nguish MH ? (theory)
± sin2 �12
2sin2 2�13 sin(2�21) sin(2|�31|)
Pee = 1� cos4 �13 sin2 2�12 sin2(�21)� sin2 2�13 sin2(|�31|)� sin2 �12 sin2 2�13 sin2(�21) cos(2|�31|)
Reactor neutrino experiment
�e + p� e+ + n
�e
Flux @ Reactor @ Detector �e�e
=
Baseline (L km)
Pee
�
How to dis)nguish MH ? (experiment)
Reactor Detector
We esImate the sensi)vity to dis)nguish the MH difference.
Method analysis �2
Baseline Length
MH difference disappears aJer shiJ in @ L = 30km.
|�m231| |�m2
31|+�
|�m231|+�|�m2
31|
|�m231|
L = 30km
L = 50km
What affects the sensi)vity ?
MH difference remains aJer shiJ in @ L = 50km. |�m231|
Short Baseline ( L < 50km ) is less sensi)ve
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
Energy Resolu)on
b: systematic error parta: statistical error part
w/o Resolu)on a = 6%
|�m231|+�
ShiJ in |�m231|
a = 6%
�EE
=
��a�E
�2
+ b2
�E �= 0
What affects the sensi)vity ?
Energy Resolu)on affects significantly.
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
opImal Baseline L ~ 50km
a < 3% is required for
. (��2)min � 9
Results 1-‐a
Sta:s:cal part of Energy ResoluIon
�EE
=
��a�E
�2
+ b2
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 opImal L
b < 1% is required for
. (��2)min � 9
20GW 5kton 5yrs
Sensi)vity for Mass Hierarchy Results 1-‐b
Systema:c part of Energy ResoluIon
�EE
=
��a�E
�2
+ b2
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
Results 2
FiZed parameter values are not so sensi:ve to the Energy Resolu:on
~ 0.5% accuracy can be achieved for sin2 2�12,�m221,�m2
31
Summary
We have studied the sensi:vity of Medium Baseline Reactor Experiments for MH determina:on.
For 20GW 5kton 5yrs exposure,
50km Baseline Length is opImal
2-‐3% sta:s:cal error 1% systema:c error
0.5% accuracy is achieved for Neutrino parameters
of Energy Resolu:on is required
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
Sta)s)cal Fluctua)on is considered.
20GW 5kton 5yrs �n �n
We can expect for 15yrs run | a = 2% 50yrs run | a = 3%
3�