Transcript Superbeam long baseline experiments

100830
Neutrino Summer School
@Tokai
Superbeam long baseline
experiments
Takashi Kobayashi
KEK
3 flavor mixing of neutrino
Flavor eigenstates
e


U MNS
1

 0
0

 e 
m1
 1 
  Unitary matrix  
    U MNS 2 
 
 
  
 3
0
0
 c 23
 s 23
 s 23
 c 23
   c13

0

   s e i
13

6 parameters
q12, q23,
q13,

Dm122, Dm232, Dm132
0
 s13 e
Mass eigenstates
m2
m3
 i
1
0
0
 c13
   c12

   s12

 0
 s12
 c12
0
0

0
1 
Dmij=mi2-mj2
c ij  cos( q ij ), s ij  sin( q ij )
2
Known and Unknowns
Solar & Reactor
•q12~33o
•Dm122~0.00008eV2
Atomspheric + Acc
•q23~45o
•Dm232~0.0025eV2
Unknown!
•q13<10o
• (Dm132~Dm232)?
• ???
T.Kobayashi (KEK)
e??
3
2
OR
1
Mass hierarchy
3
Unknown properties of neutrino

q13?
Last unknown mixing angle
 T2K, NOvA, Double Chooz, RENO, DayaBay

CP invariance ?
 Mass hierarchy ?


Absolute mass


Next generation
accelerator based
expriemtns
Tritium beta decay, double-beta
Majorana or Dirac?

Double-beta
4
Toward unraveling the
mystery of matter
dominated universe
5
Sakharov’s 3 conditions
To generate Baryon asymmetry in the unverse
 There is a fundamental process that violates
Baryon number
 C and CP invariance is violated at the same
time
 There is a deviation from thermal
equilibrium acting on B violating process
6
Toward origin of matter dominated
universe
Quark sector CPV is found to be not sufficient
for reproducing present baryon content
 Scenario for baryogenesis through lepton CP
violation: Leptogenesis



CPV in lepton sector is responsible for B genesis
CPV in neutrino oscillation could provide a
key to unravel mystery of origin of matter
7
Let’s find CPV in lepton sector

I give you
1000億円 or
 1.2 Billion USD
 755M GBP
 55 Billion INR
 1,401 Billion Won
 2,130 Billion Peso
 7.9 Billion 元
 918 Million Euro
 35 Billion Ruble
 1.2 Billion CHF

Let’s design an experiment to
search for CPV in lepton
sector
If you find any good
idea, let’s write a paper!
One condition: Within 10years
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How? …. : Q1
Do we really need oscillation phenomena to
probe CPV??
 Can’t we attack CPV in an experiment which
fit in an experimental hall like such as Kaon
CPV or B CPV
 Why??

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Measuring CPV in quark sector
VCKM u,c,t
s,b
W
d
VCKM u,c,t
VCKM
W
W
VCKM
u,c,t
s,b
VCKM
VCKM
Through loop diagram
 Amplitude ∝ (mu,c,t/MW)2



Please calculate
Since quark is heavy (especially top), this
process becomes measureable
10
How about lepton sector?
g
Example: eg
W
e,,

VMNS
VMNS
e
Amplitude ∝ (m/MW)2
 Standard model process STRONGLY
suppressed


Thus, good field to search for physics beyond
standard model
11
Oscillation
1
l 2
l’
3
U
 l t  
e
MNS
li
 iE i t
i i l
 iE i t
m i i l
i
 m  l t  
e
i
12
Oscillation (cont)
 m  l t  
e
 iE i t
m i i l
i
If Ei are same for all mass eigenstates E
 m  l t   e
 iEt

m i i l
i
e
 iEt
m l  e
 iEt
 ml
Ei’s are same, no oscillation, in other word, Ei’s are different, we can probe mixing
matrix through oscillation
Difference of Ei, ie, phase advance difference is essential
Pl  m   m  l t 
2


e


 i Ei  E j t
U
*
mi

*
U li U mj U lj

i, j
e
 i ( Ei  E j )t
2
~e
D m ij  m i  m j
2
2
2
 i D m ij L / 2 E
 O (1)  L  O (100 km )
For Dm2~10-3eV2
13
B.Kyser, in this SS
14
Q2: What oscillation process is
best?
OK, now, we somehow understand we need
(long baseline) oscillation phenomena to probe
matrix elements and attack CPV.
 What type of oscillation is best?

Fundamental physics reason
 Experimental feasibility

15
Disappearance ? Appearance?
Oscillation probability
 m  l t  

e
 iE i t
m i i l
i
Disappearance case
 l  l t  

e
 iE i t
l i i l
i

e
 iE i t
U li
2
i
There is no place for complex phase  in UMNS to appear
Disappearance has no sensitivity on (standard) CPV
16
Appearance

Conventional  beam (~GeV)

  e


  


Not yet discovered
Dominant oscillation mode
Neutrino factory/Beta beam (~10GeV)
e  
 e  

Next talks
17
e vs  appearance
Oscillation probability (w/ CPV)
P  A  A sin 
2
CP conserved
part
CPV part
Relative effect of CPV
CPV / CPC  A sin 


  case,
A
2
 sin 
A

probability A∝sin22q23, is known to be large, relative effect of
CPV becomes small

Also experimentally, identification of nt (out of lots of nm
interactions ) is not easy
For nue appearance, A∝sin22q13 is known to be small

 Large CPV effect expected
18
Matter effect
Interactions through propagation in matter
e
e
NC
X
Z
Z
X


X
X
X
e-
e
CC

Z
X

W
e-
e
19
Matter effect
 e
d 
i
 
dt 
 

 e


  H tot  



 





H tot  U MNS
 E1







E2

 VW
 1

U MNS   0
 0
E 3 

0
0
0
0

0
0 
Relative size of effect ∝ E
Change sign when Dm2 sign
change: Can probe sign
Change sign when 
⇔bar: Fake CPV effect
20
Oscillation probabilities
when
2
2
 D m 122  D m 23
 D m 13

E
2

 D m 23

L
contribution from Dm12 is small
 disappearance (LBL/Atm)
P  x  1  cos q 13  sin
4
3
(No CPV & matter eff. approx.)
2
Dm232
q23 and Dm232
2q 23  sin
2
1 . 27 D m
2
23
L / E
2
1

~1
e appearance (LBL/Atm)
P  e  sin q 23  sin
2
~0.5
q13 and Dm132
2
2q 13  sin
Pe  x  1  sin
≪1
2q 13  sin
1 . 27 D m
2
13
L / E
Pure q13 and Dm132
e disappearance (Reactor)
2
2
2
1 .27 D m
2
13
L / E


21
e appearance & CPV
Main
CP-odd
Solar
Matter
, a-a for     e
Matter eff.:
a  7 . 56  10
ACP
D m 12 L sin 2q 12



 sin 
PP
E
sin q 13
PP
2
# of signal ∝ sin2q13 (Stat err∝sinq13),
CP-odd term ∝ sinq13
5

  E

2
 
[eV ]  
3  
[
g
cm
]

  [ GeV
Sensitivity indep. from q13
(if no BG & no syst. err) 22


]
All mixing angle need to be non-zero
Leading
CP-odd
, a-a for     e
+ other terms..
Matter eff.: a  7 . 56  10
CPV effect  sin
5

  E

2
 
[eV ]  
3  
 [ g cm ]   [ GeV
  s12  s 23  s13
(where sinq12~0.5, sinq23~0.7, sinq13<0.2)
Same as Kobayashi-Maskawa model which require 3x3 to incorporate CPV
Takashi Kobayashi (KEK), PAC07
23


]
CPV vs matter effect
e osc. probability w/ CPV/matter
295km
P  P (    e )
P  P (    e )
730km
@sin22q13=0.01
Smaller distance/lower energy  small matter effect
Pure CPV & Less sensitivity on sign of Dm2
Combination of diff. E&L help to solve.
24
Lepton Sector CP Violation

c12 c13
  
 i



s
c

e
c12 s13 s 23

 
12 23
     e i c s c  s s
12 13 23
12 23
   
 e 
c13 s12
i
c12 c 23  e s12 s13 s 23
i
 e s12 s13 c 23  c12 s 23
 i
s13   1 
 
c13 s 23  2 
 
c13 c 23   3 
e
Effect of CP Phase δ appear as
– νe Appearance Energy Spectrum Shape
*Peak position and height for 1st, 2nd maximum and minimum
*Sensitive to all the non-vanishing δ including 180°
*Could investigate CP phase with ν run only
– Difference between νe and νe Behavior
25
How to do experiment?
OK, we now understand
 Importance of CPV in lepton sector
 Necessity of oscillation to probe CPV
 What process is suited for CPV measurement
 Behavior of oscillation probabilities and
relevant physics
So, now, let’s consider more on experimentation!
26
Super Beam
Proton
Beam
Target
Focusing
Devices
p,K
Decay Pipe


Beam Dump
Conventional neutrino beam with (Multi-)MW proton beam
(Fact)
 Pure  beam (≳99%)
 e (≲1%) from pe chain and K decay(Ke3)
 / can be switched by flipping polarity of focusing
device
Strongly motivated by high precision LBL  osc. exp.
27
High intensity narrow band beam
-- Off-axis (OA) beam -Far Det.
q
TargetHorns Decay Pipe
(ref.: BNL-E889 Proposal)
 flux
E(GeV)
Decay Kinematics
1
E(GeV)
1/gp~q
max
E
[ GeV ] 
5
2
Ep(GeV)
30
q [ mrad ]
Increase statistics @ osc. max.
Decrease background from HE tail28
/ flux for CPV meas.
Sign flip by
just changing
horn plarity
Example

-15%@peak

50GeV proton
At 295km
1021POT/yr
Cross sections

Cross section ∝ E


Higher energy 
higher statistics
Anti-neutrino cross
section smaller than
neutrino by ~1/3


Why?
Take ~3 times more
time for anti-neutrino
measurements to
acquire same
statistics as neutrino
e appearance search

p0
e
Back ground for e appearance search
• Intrinsic e component in initial beam
• Merged p0 ring from  interactions
31
“Available” technologies for huge detector
Good at low E (<1GeV)
narrow band beam
Good at Wideband beam
Liq Ar TPC
 Aim O(100kton)
 Electronic “bubble chamber”



Neutrino energy reconstruction
by eg. total energy




Can track every charged particle
Down to very low energy
No need to assume process type
Capable upto high energy
Good PID w/ dE/dx, pi0 rejection
Realized O(1kton)
Water Cherenkov
 Aim O(1000kton)
 Energy reconstruction assuming
Ccqe




Effective < 1GeV
Good PID (/e) at low energy
Cherenkov threshold
Realized 50kton
32
Neutrino Energy E reconstruction in
Water Cherenkov
2

CC quasi elastic reaction
-
 + n →  + p
q
2
4
  c ro s s s e c tio n s (1 0
4 .5
m N  E   p  cos q 
-
 + n →  + p + p

p
-38
cm )


(E, p)
E 
m NE  m  2
p
inelastic
3 .5
3
2 .5
2
In e la s tic
1 .5
1
QE
0 .5
CCqe
0
0
1
2
3
4
5
E (G e V )
ql
p

(E, p)
2 approaches for CPV (and sign(Dm2) )

Energy spectrum measurement of appeared e
Only w/ numu beam (at least early part)
 Measure term ∝ cos (and sin)



Assume standard source of CPV ( in MNS)
Cover 2nd oscillation maximum (higher sensitivity on
CPV)

Higher energy = longer baseline favorable
Wideband beam suited
 Liq Ar TPC is better suited


Difference between P(numunue) and
P(numubar  nuebar)
Measure term ∝ sin
 Not rely on the standard scenario

34
•
Off-axis angle
– On-Axis: Wide Energy Coverage,
○Energy Spectrum Measurement
×Control of π0 Background
– Off-Axis: Narrow Energy Coverage,
○Control of π0 Background
×Energy Spectrum Measurement
→ Counting Experiment
Baseline
– Long:
○ 2nd Osc. Max. at Measurable Energy
× Less Statistics
? Large Matter Effect
– Short:
○ High Statistics
× 2nd Osc.Max.Too Low Energy to Measure
? Less Matter Effect
Oscillation probability
•
 flux
Angle and Baseline
OA0°
OA2°
OA2.5°
OA3°
νμ  νe oscillation probability
CP=0
CP=90
CP=270
-3
Dm312 = 2.5x10 eV2
sin22q13 = 0.1
No matter effects
35
(E/L)
“Available” beams
36
37
FNAL possible future Plan
38
CERN future possibilities
Present accelerator complex

Under discussion
Various POSSIBLE scenarios
39
CERN possibilities
40
Possible scenarios in Japan
Okinoshima
Korea
1000km
1deg. Off-axis
658km
0.8deg. Off-axis
Kamioka
295km
2.5deg. Off-axis
41
Scenario 1
•Cover 1st and 2nd Maximum
•Neutrino Run Only 5Years×1.66MW
•100kt Liq. Ar TPC
-Good Energy Resolution
-Good e/π０discrimination
•Keeping Reasonable Statistics
νeSpectrum
sin22θ13=0.03,Normal Hierarchy
δ=0°
δ=90°
δ=180°
δ=270°
CP Measurement Potential
3s
Okinoshima
Beam νe
Background
658km
0.8deg. Off-axis
NP08, arXiv:0804.2111
42
Scenario 2
•Cover 1st Maximum Only
295km
•2.2Years Neutrino+7.8Years anti-Neutrino Run
2.5deg. Off-axis 1.66MW
<E>~0.6GeV
•540kt Water Cherenkov Detector
Kamioka
signal+BG
+ee BG
+ BG
Er
ec

Er
ec
=p/2
CP sensitivity
sin22q13

sin22θ13=0.03,Normal Hierarchy
3s
deg.
Er
ec
Fraction of 
=0
Tokai
Er
ec
3s
sin22θ13
K.Kaneyuki @NP08
43
Site studies in Europe
44
45
FNAL possibilities
NOvA
700kW
15kt Liquid Scintillator
Under construction
NSF’s proposed
Underground Lab.
DUSEL
810 km
735 km
2.5 msec
MiniBooNE
SciBooNE
MINOS
NOvA
MINERvA
MicroBooNE
1300 km
~300 kton
Water Cerenkov ~50 kton Liquid Ar TPC
Project X: ~2 MW
Combination of WC and LAr
US Superbeam Strategy: Young-Kee Kim, Oct. 1-3, 2009
FNAL-DUSEL potential
To realize the experiments
Need
 Finite (reasonable) q13  T2K, NOvA,
Reactors!
 High power (>MW) neutrino beam
 Huge high-sensitivity detector
  YOUR CHALLENGE
 OR YOUR NEW IDEA!
48
Summary


Properties of neutrino are gradually being revealed
However still yet far unknown than quarks






CPV, mass hierarchy, etc.
Especially, CP symmetry could be a critical key to
answer the fundamental question: What is the origin of
matter in the universe
Future superbeam long baseline oscillation experiments
have chance to discover CPV effect (if q13 is large
enough to be detected in present on-going experiments)
Already many studies and developments (beam,
detectors) are being made around the world to realize
the experiments
Lot’s of challenges and funs forseen
Let’s enjoy!
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