Talk @ KEKPH 2013

1. 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

2. Introduc7on
2

3. Mass
Hierarchy
3
P( e e) =
3
i=1
Uei exp i
m2
i
2Ei
Uei
2
= P( e e)
m2
31 = m2
3 m2
1 > 0 m2
31 = m2
3 m2
1 < 0
m2
31 < 0
m2
31 > 0

4. 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

5. MH
difference
in
spectrum
e

6. Sensi7vity

7.
analysis
The
theore2cal
predic2on
is
fi7ed
to
the
Data,
assuming
NH
or
IH.
2
min(NH) 2
min(IH)
Nfit
i = dEvis
NpT
4 L2
Ethr
dE (E ) Pee IBD G(E , Evis)
FiAng
parameters
are
12, 13, m2
21, | m2
31|, fsys
Penalty
term
Nfit
i
2

8. 0
5
10
15
20
25
30
35
40
10 20 30 40 50 60 70 80 90 100
(
2
)min
L [km]
a = 2% NH
3% NH
4% NH
5% NH
6% NH
Sensi7vity
to
the
Mass
hierarchy
16.5GW
18kton
5yrs
Current
value
NH
a 7%
b = 0
b 1%
E
E
=
a
E/MeV
2
+ b2

9.
Effect
of
b
term
E
E
=
a
E
2
+ b2
16.5GW
18kton
5yrs
20 30 40 50 60 70 80 90 100
L [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
(
2
)min
L [km]
b
=
0%
b
=
1%
Sensi7vity
40%
Imrovement
of
b
term
is
also
important

10. 0
5
10
15
20
25
30
35
40
10 20 30 40 50 60 70 80 90 100
(
2
)min
L [km]
a = 2% NH
3% NH
4% NH
5% NH
6% NH
Sensi7vity
to
the
Mass
hierarchy
16.5GW
18kton
5yrs
Current
value
NH
a 7%
( m2
31) Small
Flux
b = 0
b 1%
E
E
=
a
E/MeV
2
+ b2

11. Interference
Effect

12. 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

13. RENO
Reactor
mul7-­‐cores
Mul7-­‐reactor
interference
16.5GW
18kton
5yrs
a
=
3%,
b
=
0.5%
E
E
=
a
E
2
+ b2
RENO
Reactor
0
1
2
3
4
5
6
7
8
9
10
11
( 2)min
All
Reactors

14. 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.
E
E
=
a
E
2
+ b2
Interference
among
reactor
cores
significantly
affects
the
sensi2vity.
Many
Efforts
for
MH
determina2on
have
started
!

15. Backup
Slides
15

16. Energy
Distribu7on
e
@
Detector
e
near
dNfar
dEvis
=
NpT
4 L2
Ethr
dE (E ) Pee IBD G(E , Evis)
Pee
far
L

17. 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

18. Effects
of
to
the
sensi7vity
| m2
31|
L
=
30km
| m2
31|
| m2
31|
L
=
50km
Baseline
should
be
long
enough
| m2
31|+2
fit
2
fit | m2
31|+

19. Effect
of
Energy
Resolu7on
Evergy
Resolu7on
affects
the
sensi7vity
significantly.
E
E
=
a
E

20. Pull
Factors
of
fidng
parameters
-0.25
0
0.25
0.5 sin
2
2 12
2% NH
IH
3% NH
IH
6% NH
IH
-0.25
0
0.25
0.5 sin2
2 13
-0.25
0
0.25
0.5
pullfactor
m2
21
-0.25
0
0.25
0.5
| m
2
31|
-0.25
0
0.25
0.5
10 20 30 40 50 60 70 80 90 100
L [km]
fsys

21. 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%
...

22. Reactor
neutrino
experiment
(contd.)
22
Energy
Resolusion
Energy
Scale
Unc.
~
2%
Reconstructed
E

23. 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)

24. 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