6 January 2004 EFI Faculty Lunch Future Neutrino Oscillation Experiments • Neutrino oscillations, CP violation, and importance of 13 • Accelerator vs. reactor experiments • Future reactor experiments to measure sin 2 2 13 Ed Blucher
Jan 15, 2016
6 January 2004 EFI Faculty Lunch
Future Neutrino Oscillation Experiments
• Neutrino oscillations, CP violation, and importance of 13
• Accelerator vs. reactor experiments• Future reactor experiments to measure
sin2213
Ed Blucher
Neutrino Oscillations
• During last few years, oscillations among different flavors of neutrinos have been established; physics beyond the S.M.
• Mass eigenstates and flavor eigenstates are not the same (similar to quarks):
1 2 3 1
1 2 3 2
1 2 3 3
e e e eU U U
U U U
U U U
mass eigenstatesflavor eigenstates
• Raises many interesting questions including possibility of CP violation in neutrino oscillations.
• CP violation in neutrino sector could be responsible for the matter-antimatter asymmetry.
MNSP matrix
Quark and Neutrino Mixing Matrices
1 2 3 1
1 2 3 2
1 2 3 3
1
2
3
e e e eU U U
U U U
U U U
B B
B B B
B
S
B B
1
1
1
ud us ub
cd cs cb
td ts tb
d V V V d
s V V V s
b V V V b
S S d
S S s
S S b
2 Flavor Neutrino Mixing
1
2
cos sin
sin cose
The time evolution of the flavor states is:1 2
1 2
1 2
1 2
cos sin
sin cos
iE t iE te
iE t iE t
e e
e e
For a beam that is pure at t=0,
222 2
2 2 22 1
( ) sin 2 sin ,4
where m
e e
mP L
E
m m
1 2 3
1 2 3
1 2 3
12 12 13 13
12 12 23 23
13 13 23 23
cos sin 0 cos 0 sin 1 0 0
sin cos 0 0 1 0 0 cos sin
0 0 1 sin 0 cos 0 sin cos
CP
CP
e e e
i
i
U U U
U U U U
U U U
e
e
12 ~ 30° 23 ~ 45°sin2 213 < 0.2 at 90% CL
MNSP Matrix
What is e component of 3 mass eigenstate?
Minakata and Nunokawa, hep-ph/0108085
CP Violation in Neutrino Oscillations
P( e ) P( e ) 16s12c12s13c132 s23c23 sin sin
m122
4EL
sin
m132
4EL
sin
m232
4EL
Methods to measure sin2213• Appearance e (Accelerator Exp)
– Use fairly pure, accelerator produced beam with a detector at long distance (300 km - 900 km) from the source
• Look for the appearance of e events
• Use near detector to measure background es (beam and misid)
• Disappearance (Reactor Exp)
– Use a set of reactors as a source of e's with a detector at few km
• Look for a non- 1/r2 behavior of the e rate
• Use near detector to measure the unoscillated flux
Diablo Canyon, CA
150m 1500m
overburden
22 2 13
13( ) 1 sin 2 sin4e e
m LP small
E
22 2 2 13
23 13( ) sin sin 2 sin 4e
m LP not small
E
Accelerator and reactor measurements of 13
Accelerator experiments measure:
231
221
m
m
2 213 311 ( ) sin 2 sine eP
Reactor measurement of 13 is independent of matter effects and CP violation:
2
4ij
ij
m L
E
Reactor Measurements of Neutrino Oscillations
0.00
10.00
20.00
30.00
40.00
50.00
60.00
1.50 2.50 3.50 4.50 5.50 6.50 7.50 8.50 9.50
Enu (MeV)
Arb
itra
ry S
cale
Neutrino Flux Cross Section # of Events
Reactors are copious sources of per second.21; ~ 10 e e
Detection of antineutrino by e p e n
followed by (2.2 ); ~ 210 secn p d MeV
or for Gd-loaded scintillator8 of s; ~ 30 secn Gd MeV
Long history of neutrino experiments at reactors
Current interest is focused mainly on possibility of measuring
20 m
KamLAND
6 mCHOOZ
2atmm 2
solarm
2 22 2 2 213 12
13 12( ) 1 sin 2 sin sin 2 sin4 4e e
m L m LP
E E
Reactor Measurements of ( )e eP
Future: Search for small oscillations at 1-2 km distance (corresponding to 2 ).atmm
Reactor experiments allow direct measurementof sin22: no matter effects, no CP violation,almost no correlation with other parameters.
Sensitivity goal: sin22~0.01.Level at which long-baseline “superbeams” can be used to measure mass hierarchy, CPV;~ sensitivity goal of proposed accel. expts. Distance to reactor (m)
Pee
2 3 213
213
2.5 10
sin 2 0.04
3.5
m eV
E MeV
Previous Reactor Experiments
• CHOOZ and Palo Verde Experiments– Single detector experiments– Detectors used liquid scintillator with
gadolinium and buffer zones for background reduction
– Shielding:• CHOOZ: 300 mwe• Palo Verde: 32 mwe
– Fiducial mass:• CHOOZ: 5 tons @ 1km,
5.7 GW– ~2.2 evts/day/ton with
0.2-0.4 bkg evts/day/ton – ~3600 events
• Palo Verde: 12 tons @ 0.85km, 11.6 GW
– ~7 evts/day/ton with2.0 bkg evts/day/ton
– ~26000 events
CHOOZ Systematic Errors
CHOOZ
Target: 5 ton Gd-doped scintillator
Is it possible to improve the Chooz experiment by order of magnitude (i.e., sensitive to sin22 ~ 0.01)? Add second detector; bigger detectors; better control of systematics.
~200 m ~1500 m
What systematic error is attainable?• Efficiency and energy calibration strategy (movable detectors?)• Backgrounds• Multiple reactor cores• Site / depth• Choice of scintillator (stability of Gd-loaded scintillator)• Size, distance of detectors
• Counting Experiment– Compare number of events in near and far
detector• Energy Shape Experiment
– Compare energy spectrum in near and far detector
Normalization and spectral information
E (MeV)
E (MeV)
Predicted spectrum 13=0
Observed spectrum sin2213=0.04
Analysis Using Counting and Energy Spectrum(Huber et al. hep-ph/0303232)
Counting exp. region
Spectrum & Rate region
(12 ton det.) (250 ton det.)
90%CL at m2 = 3×10-3 eV2
cal relative near/far energy calibration
norm relative near/far normalization
Scenarios:Reactor I = 12ton×7GW×5yrsReactor II = 250ton×7GW×5yrs
Worldwide interest in two-detector reactor experiment
Workshops:Alabama, June 2003Munich, October 2003Niigata, Japan, March 2004
Based on early workshops, a whitepaper describing physics possibilities of reactor experimenthas been written.
Sites under discussion:
•Kraznoyarsk (Russia)•Chooz (France)•Kashiwazaki (Japan)•Diablo Canyon (California)•Braidwood, Byron (Illinois)•Wolf Creek (Kansas)•Brazil•Taiwan•China
Ref: Marteyamov et al, hep-ex/0211070
Reactor
Detector locations constrained by existing infrastructure
Features - underground reactor - existing infrastructure
~20000 ev/year~1.5 x 106 ev/year
Kr2Det: Reactor 13 Experiment at Krasnoyarsk
Kashiwazaki -7 nuclear power stations; world’s most powerful reactors
- requires construction of underground shaft for detectors
near near
far
Kashiwazaki-KariwaNuclear Power Station
Proposal for Reactor 13 Experiment in Japan
near near
far
70 m 70 m
200-300 m
6 m shaft, 200-300 m depth
Kashiwazaki: Proposal for Reactor 13 Experiment in Japan
The Chooz site, Ardennes, France
… Double-CH1313Z …
The Chooz site
Near site: D~100-200 m [severall options under study]Far site: D~1.1 km, overburden 300 mwe [former experimental hall]
Type PWR
Cores 2
Power 8.4 GWth
Couplage 1996/1997
(%, in to 2000)
66, 57
Constructeur
Framatome
Opérateur EDF
?
Chooz, 2x10 tonnes, D1=0.7 km, D2=1.1 km, 3 ans (70 kevts) sin2(213)<0.037
•Positive signs from EDF for reusing the former CHOOZ site. Near site civil engineering •2x11.5 tons, D1=100-200m, D2=1050m. Sensitivity: 3 years sin2(213) < ~0.03
CHOOZ-Far
CHOOZ-Far detector
7 m
3.5 m
Existing CHOOZ tub
CHOOZ-Near new Laboratory
~5- 15 m
High-Z material
~10-15 m
U.S. Nuclear Power Plants
Braidwood, Illinois 7.17 GWBraidwood, Illinois 7.17 GW24 miles SW of Joliet
Braidwood site
• Powerful: Two reactors (3.1+ 3.1 GW Eth) • Overburden: Horizontal tunnel could give 800 mwe shielding• Infrastructure: Construction roads. Controlled access. Close to wineries.
Diablo Canyon Nuclear Power Plant
1500 ft
2 underground detectors
•We’ve formed a small collaboration to develop a proposal for amidwest site:Chicago, Columbia, ANL, FNAL, Kansas, Michigan, Oxford, Texas
Chicago involvement:Kelby Anderson, Ed Blucher, Juan Collar, Jim Pilcher, Matt Worcester (postdoc), Erin Abouzaid (grad), Abby Kaboth (undergrad), Jennifer Seger (undergrad)
•Significant effort also underway at LBNL to investigate feasibilityof experiment at Diablo Canyon.
Conclusions
• Extremely exciting time for neutrino physics!• The possibility of observing CP violation in the
neutrino sector presents a great experimental challenge.
• Reactor and accelerator experiments are complementary.
• Reactor experiment has potential to be faster, cheaper, and better for establishing value of .
Was baryogenesis made possible by leptonic CP violation?
Leptogenesis may have been the result of direct CP violationin decays of heavy Majorana particles:
( ) ( )N H N H
This antilepton excess in converted to a baryon excess throughnonperturbative Standard Model B-L conserving processes.
- Fukugita and Yanagida, Phys. Lett. B174 (1986)