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)