Chasing θ13with new experiments at nuclear reactors

Thierry Lasserre Saclay

NuFact04, OsakaJuly 26 2004

T.L. (Saclay) - NuFact04 -

The neutrino sector[ m221 - θ12] – [ m232 - θ23] – sign( m232) - θ13 - δ

superbeam ν+

reactor ν

sin2(2θ13) β & ββ0ν decays ?

T.L. (Saclay) - NuFact04 -

Measurement at reactors&

complementarity with LBL

T.L. (Saclay) - NuFact04 -

νe disappearance experiment

Pth= 8.5 GWth, L = 1,1 km, M = 5t (300 mwe)

Best current constraint: CHOOZ

World best constraint !

@∆m2atm=2 10-3 eV2

sin2(2θ13)

T.L. (Saclay) - NuFact04 -

θ13 & beam experimentsLBL νµ disappearance : sin2(2θ23) 2 solutions : θ23 & π/2-θ23

|∆m213| 2 solutions m1>m3 or m3>m1

Appearance probability :

• K1,K2,K3: constants known with experimental errors)• dependence in sin(2θ23), sin(θ23) 2 solutions• dependence in sign(∆m231) 2 solutions• δ-CP phase [0,2π] interval of solutions

P(νµ→ νe) ~ K1 sin2(θ23 ) sin2(2θ13 )+ K2 sin(2θ23 ) sin(θ13 ) sign(∆m231) cos(δ)

K3 sin(2θ23 ) sin(θ13 ) sin (δ)

θ13 & reactor experiments• ~ a few MeV only disappearance experiments

sin2(2θ13) measurement independent of δ-CP

• 1-P(νe→ νe) = sin2(2θ13)sin2(∆m231L/4E) + O(∆m221/∆m231)

weak dependence in ∆m221• a few MeV νe + short baselines negligible matter effects (O[10-4] )

sin2(2θ13) measurement independent of sign(∆m213)si

n2(2

θ13

)

P(νµ→ νe)

ν beam

reactor

T.L. (Saclay) - NuFact04 -

CP-δ phase induced ambiguity

0

0.01

0.06 0.1 0.14

0.03

0.05

0.07

sin2(2θ13)

P(ν µ

ν e)

⎟⎟⎠

⎞⎜⎜⎝

⎛±≈→

)sin(2θδsin 0.11)(2θsin

21)νP(ν

1313

2eµ

T2K measurement

()P

sin δ correlation

T.L. (Saclay) - NuFact04 -

θ23 induced ambiguity

0

0.01

0.06 0.1 0.14

0.03

0.05

0.07

sin2(2θ13)

P(ν µ

ν e)

T2K measurement

⎩⎨⎧

==

⇒=0.4)(θsin0.6)(θsin

0.95)(2θsin23

223

2

232

reactor measurement

LBL + reactor combination might help to solve the θ23 degeneracy

T.L. (Saclay) - NuFact04 -

Improving CHOOZ is difficult !

T.L. (Saclay) - NuFact04 -

50 years of reactor neutrino experiments …1956 Discovery of neutrinos @Savannah River - First detection of reactor neutrinos1990’s Reactor neutrino flux measurements1995 Nobel Prize to Fred Reines2002 Discovery of massive neutrinos and oscillations confirmed by KamLAND

From discovery to metrology ! G. Mention (APC)

Near detector Far detector

T.L. (Saclay) - NuFact04 -

One nuclear plant & two detectors

Nuclear reactor

1,2 core(s) ON/OFF : ok4 cores ON/OFF : no !

Near detector

5-50 tons> 50 mwe

Far detector

5-50 tons> 300 mwe

D1 = 0.1-1 km D2 = 1-3 km

νe νe,µ,τ

Isotropic νe flux (uranium & plutonium fission fragments) Detection tag : νe + p e+ + n, ~ 4 MeV, Threshold ~1.8 MeVDisappearance experiment: suppression+shape distortion between the 2 detectors2 IDENTICAL detectors (CHOOZ, BOREXINO/CTF type, KamLAND)

• Minimise the uncertainties on reactor flux & spectrum (2 % in CHOOZ)• Cancel cross section uncertainties • Challenge: relative normalisation between the two detectors < 1% !

T.L. (Saclay) - NuFact04 -

Improving CHOOZ is difficult …@CHOOZ: R = 1.01 ± 2.8%(stat)±2.7%(syst)

StatisticsIncrease luminosity L = ∆t x P(GWth) x Np(target)Increase fiducial volume & exposure ~2700 events in CHOOZ but >40,000 for the next experiment σ < 0.5%

Experimental error 2 detectors cancel neutrino flux and cross section systematic uncertainty [~2%]Identical detectors decrease detector systematic uncertainties [100 in the new experiment)Uncorrelated background (measurement in-situ) – Correlated backgrounds (µ induced) Underground site required: >300 m.w.e for the far site to improve CHOOZS/N equivalent for Near and Far detector (near detector could be shallower)Reactor ON/OFF measurement 1, 2, 4, or up to 7 reactor cores ?

T.L. (Saclay) - NuFact04 -

nepe +→++ν

Reactor antineutrino detection

prompt event: delayed event:

MeV)2.2(γ+→+ dpnEprompt ≅ Eν − En − 0.8 MeV

• Prompt e+, EP=1-8 MeV, visible energy

• Delayed neutron capture on Gd, ED=8 MeV

• Prompt(β/γ) - Delayed(β/γ) pulse shape discrimination

Time correlation: τ ∼ 30µsec

Space correlation: < 1m3

Anti-νe tag: νe + p e+ + n, Q~1.8 MeV Threshold

Or Gd capture (8 MeV)

T.L. (Saclay) - NuFact04 -

Why two identical detectors …un

load

edGd

~0.1

%

scintilla

tor

ν signal No ν signal

e+

n

Gdn

Gd

e+

e+

H

n

e+

H

n

ε=

0 % In

tera

ctio

n ν

ε=

100

%

spill in/out effect

Acrylic vessel

A ~1% irreducible systematic error from the spill in/out effect Boundary effect 2 identical inner vessels

Scintillator doped with 0.1% Gd MUST be perfectly stable over the life time of the experiment (>5 years)

Fiducial volume

T.L. (Saclay) - NuFact04 -

Observable: e+ spectrum(Double-CHOOZ configuration)

sin2(2θ13)=0.04sin2(2θ13)=0.1sin2(2θ13)=0.2

sin2(2θ13)=0.04sin2(2θ13)=0.1sin2(2θ13)=0.2

∆m2atm = 2.0 10-3 eV2

Near Detector: ~ 1.8 106 events-Reactor efficiency: 80%-Detector efficiency: 80%-Dead time: 50%

Far Detector: ~ 34 000 events-Reactor efficiency: 80%-Detector efficiency: 80%

E (MeV) E (MeV)

Even

ts/2

00 K

eV/3

yea

rs

T.L. (Saclay) - NuFact04 -

Example of νe oscillation at reactor(Double-CHOOZ configuration )

Rate + shape information if θ13 not too small

@1,05 km

Far/

Nea

r en

ergy

bin

rat

io

Note: optimum baseline ~1.5km

T.L. (Saclay) - NuFact04 -

Detector size scale

Borexino300 t

KamLAND1000 t

Reactor/θ13Example ~20 t

CHOOZ5 t

DoubleCHOOZ

&KASKA

(10 tons)

X 2

Angra, Daya-Bay, Braidwood

T.L. (Saclay) - NuFact04 -

90% C.L. sensitivity if sin2(2θ13)=0

Reactor1 (0.5 km, 2.3 km): ~13 tonsPXE x 10 GW x 3 years sin2(2θ13)

T.L. (Saclay) - NuFact04 -

Huber, Lindner, Schwetz & Winter (‘extremum’ of projection of the χ2 manifold on the sin2(2θ13) axis)

Double-CHθ13θ13Z

sin2(2θ13) at LBL & reactors

CHOOZ alone90% C.L

@∆m2=2.0 10-3 eV2

(3 ktons ?)

T.L. (Saclay) - NuFact04 -

Current proposal for new reactor experiments …

T.L. (Saclay) - NuFact04 -

Nuclear reactors in the world

T.L. (Saclay) - NuFact04 -

World momentumDecember 2002: First European meeting, MPIK HeidelbergApril 2003: Second European meeting, PCC, ParisMay 2003: First international workshop, University of Alabama, USOctober 2003: Second international workshop, TUM, GermanyMarch 2004: Third international workshop, Niigata, JapanNext workshop in Brazil, January 2005

125 authors, 40 Institutions White Paper Report on Using Nuclear Reactors to search for a value of theta 13 hep-ex/0402041

T.L. (Saclay) - NuFact04 -

Which site for the experiment ?

Diablo Canyon

Braidwood

Angra

PenlyChoozCruas

Krasnoyarsk

Taiwan

Kashiwasaki

One reactor complexTwo underground cavities @0.1-1 km & ~1-2 km

Daya bay

T.L. (Saclay) - NuFact04 -

The Krasnoyarsk site: Kr2DetRussian Research Center “Kurchatov Institute”

Completely underground facility was used by the Soviets for weapons production.

Single reactor coreP=1.6 GWthON/OFF cycle [50 days ON & 7 days OFF]

No civil construction

>50 tons detectorsNear: >50 tons – 115 m – 600 mweFar: >50 tons - 1.1 km - 600 mwe

Sensitivity0.5% systematic errorsin2(2θ13) < 0.015 (∆m2 =2.5 10-3 eV2, 90% C.L.)

ProspectsVisit in summer 2003 cancelled by Russian authoritiesSite not available for “political” reasons

T.L. (Saclay) - NuFact04 -

Current proposals

Braidwood

Angra

Double-Chooz

Kaska

Daya bay

1st generation: sin2(2θ13)~0.01-0.03

2nd generation: sin2(2θ13)~0.01 + shape only analysis

T.L. (Saclay) - NuFact04 -

Braidwood (Illinois)Two reactor cores

P=2 x 3.6 GWth

Civil constructionFlat topology Near & Far: 120m shafts (10m diameter) + laboratories (25-35 M$)

Two 50 tons detectorsNear: 25-50 tons – 300 m – 450 mweFar: 25-50 tons – 1.5-1.8 km - 450 mweMovable detector (move on the surface, lift with crane)

3 years Sensitivity0.5% systematic errorNo signal: sin2(2θ13) < 0.01 (90% C.L.)

Prospects (not yet approved)Construction in 39 month - running in 2009. Cost ~45 M$Geological studies ongoing

T.L. (Saclay) - NuFact04 -

Braidwood (Illinois)

Civil construction

Detector sketch

ANL, Chicago, Columbia, FNAL, Kansas, Oxford, Pittsburgh, Texas

T.L. (Saclay) - NuFact04 -

Daya BayFour reactor cores

P=4 x 2.9 = 1.6 GWth+ two new cores for 6 GWth in 2011

Civil constructionNear: 1 km tunnel + laboratoryFar: 2 km tunnel + laboratory

~10 tons detector modulesNear: 25 tons - 300 m – 200 mweFar: 50 tons - 1.5-1.8 km - 700 mweMovable detector concept

Sensitivity0.4% systematic errorsin2(2θ13) < ~ 0.01 (90% C.L.) ?

Prospects (not yet approved)2004-05: R&D, 2006-07: Construction1 Near detector running in 2008Geological & safety studies ongoing

T.L. (Saclay) - NuFact04 -

Daya Bay

Near detector: 2 x 10 tons modulesFar detector: 4 x 10 tons modules 3 years of data takingsin2(2θ13) < ~ 0.01-0.02 (90% C.L.)

IHEP, CIAE, Tsinghua Univ., Hong Kong Univ., Hong Kong Chinese Univ, (Berkeley, Caltech)R&D

T.L. (Saclay) - NuFact04 -

Kaska (Kashiwasaki, Japan)Seven reactor cores

P=24.3 GWth2 near detector mandatory

Civil construction2 Near: ~70 m 6m shafts + laboratoriesFar: ~250 m 6m shaft + laboratory

Multiple detectors2 Near: 8 tons – 300-400 m – 100 mweFar: 8 tons - 1.3-1.8 km - 500 mwe

Sensitivity0.5% systematic errorsin2(2θ13) < 0.025 (90% C.L.)

Prospects (not yet approved)2004-05: R&D, 2006-07: Construction. Running in 2008. Cost ~20 M$Geological studies ongoing – Prototype to be built for R&D.

T.L. (Saclay) - NuFact04 -

KASKA (Japan)Tohoku Univ., Niigata Univ., Rikkyo Univ., KEK, Kobe Univ.Tokyo Institute of Technology, Tokyo Metropolitan Univ.

Sensitivity (3 years): sin2(2θ13)

T.L. (Saclay) - NuFact04 -

Near site: D~100-200 m, overburden 50-80 mweFar site: D~1.1 km, overburden 300 mwe

2Cores

EDFOpérateur

FramatomeConstructeur

66, 57(%, in to 2000)

1996/1997Couplage

8.4 GWthPower

PWRType

Chooz-Far

Chooz-Near

Double-Chooz (France)

T.L. (Saclay) - NuFact04 -

Double-Chooz featuresTwin reactor cores

N4 type P=2x4.2 GWth

Civil constructionNear: 20x10x5m experimental hallArtificial overburden

Two 10 tons detectorsNear: 100-200 m – 60-80 mweFar: 1.05 km - 300 mwe

3 years Sensitivity0.6% systematicsNo signal: sin2(2θ13) < 0.02-03 (90% C.L.)Signal: sin2(2θ13) > 0.04-05 (3σ)

Prospect (approved & funded in France)2007: far detector running 2008: near detector runningCost ~7Meuros + civil constr.

Near detector site (to be built)

Existing Far detector site

@DAPNIA

T.L. (Saclay) - NuFact04 -

The CHOOZ-far detector

CHOOZ existing pit

Non scintillating buffer: scintillator+quencher(r+0.95m, , V=100 m3)

γ-catcher: 80% dodecane + 20% PXE(acrylic, r+0,6m – V= 28,1 m3)

7 m

7 m

PMT supporting structure

Muon VETO: scintillating oil (r+0.6 m – V=110 m3)

7 m

Shielding: 0,15m steel

ν target: 80% dodecane + 20% PXE + 0.1% Gd(acrylic, r=1,2m, h = 2,8m, 12,7 m3)

@DAPNIA

T.L. (Saclay) - NuFact04 -

Reactor induced systematics

2.1%

0.6%

0.7%

1.9%

CHOOZ

O(0.1%)-Σ

O(0.1%)-E/Fission

O(0.1%)-Thermal power

O(0.1%)-Flux, cross section

Reactor

2 identical detectorLow background

FutureExperiment

Error typesystematics

2 detectors cancellation of the reactor physical uncertainties

T.L. (Saclay) - NuFact04 -

Detector induced systematics

?

1.0%

0.3%

1.2%

0.3%

CHOOZ

X

Sim.Monte-Carlo

0.25%0.25%Live time

O(0.1%)1.0%« Spill in/out » effect

0.2%0.2%Target volume

O(0.1%)1.2%% H

O(0.1%)0.3%Scintillator density

Detector

2 identical detectorLow backgrounds

FutureExperiment

Error typesystematics

M. Apollonio et. al., Eur.Phys.J. C27 (2003) 331-374

A single scintillator batch will be prepared to fill both detectors with the same apparatus

T.L. (Saclay) - NuFact04 -

Relative Normalisation: Analysis@CHOOZ: 1.5% systematic error

- 7 analysis cuts- Efficiency ~70%

Sélection cuts- positron energy [energy threshold]- e+ position/géode (30cm) [position reconstruction]- neutron energy [energy cut - calibration]- n pos./géode (30 cm) [position reconstruction]- distance e+ - n [position reconstruction]- ∆t e+ - n [neutron capture on Gd]- n multiplicity [level of accidental background]

Goal Double-CHOOZ:

T.L. (Saclay) - NuFact04 -

Attempt to compare Double-Chooz withT2K (3σ discovery potential)

sin22θ13 = 0.14 sin22θ13 = 0.08Sin2(2θ13) = 0.04

Double-CHOOZ starts with two detectors in January 2008T2K starts at FULL intensity in January 2010Assumption

From Huber, Lindner, Schwetz(hep/0405032) 90% C.L.

3σ C.L.

T.L. (Saclay) - NuFact04 -

Letter of Intent

Th. Lasserre

+ Univ. Alabama - Univ. Louisiana - Univ. Tennessee -Univ. Drexel – Argonne

T.L. (Saclay) - NuFact04 -

Double-Chooz & IAEAIAEA :Intenational Agency for Atomic Energy

Missions: Safety & Security, Science & Technology, Safeguard & VerificationControl that member states do no use civil installations with military goals (production of plutonium !)

•Control of the nuclear fuel in the whole fuel cycle *•Fuel assemblies, rods, containers * (*Anti-neutrinos could play a role!)•Distant & unexpected controls of the nuclear installations *

Why IAEA is interested to antineutrino ? •IAEA wants the « state of the art »methods for the future !•Cost issue … 10,000$/day/inspector …

AIEA wants a feasibility study on antineutrinos•Monitoring of the reactors with a Double-Chooz like detector ?•Monitoring a country – new reactors “à la KamLAND”

Double-CHOOZ-IAEA: CEA/Saclay + Subatech Nantes + Kurchatov•Perform new antineutrino spectrum @ILL reactor•Use Double-Chooz near as a ‘prototype’ for nuclear reactor monitoring•Other studies like large and very large underwater antineutrino detectors …

T.L. (Saclay) - NuFact04 -

Towards evidence of non vanishing δH

. Minakata

& H. Sugiyam

a, hep-ph/0309323• T2K: 10 years running (0.75MW beam & Super-Kamiokande)• Reactor (second generation): 103 104 GWth.ton.year

Regions consistent with the hypothesis δ=0 (90% CL)

By the reactor-LBLcombined measurement

Reactor [103 GW.t.y]@ ~1km200 tons10 GWth5 years

T.L. (Saclay) - NuFact04 -

Single reactor coreP=4.1 GWthA new core is being built (2006)

Civil constructionNear: 6x6x60m tunnel + 10x10x12m exp. hallFar: 6x6x450m tunnel + 10x10x12m exp. hall+ emergency shafts

Two >100 tons detectorNear: 300 m – 50 mwe ?Far: 1.35 km - 600 mweNon movable detectors concept

Sensitivity5 years >103 GWth.t.ysin2(2θ13) < 0.01 (90% C.L.)1% systematic errorShape only analysis

2nd generation project: Angra (Brazil)Argonne + Brazil : CBPF, UNICAMP, USP, PUC-RIO

T.L. (Saclay) - NuFact04 -

Conclusion & outlookA new reactor neutrino experiment could provide an evidence of the oscillation in the (1,3) sector in 2009

Reactor & LBL programs provide independent and complementarymeasurements of θ13. But current proposals have low synergy …

Of course reactor experiments won’t replace the rich LBL program. However, a preliminary value of θ13 might help to design the best CP-δdetector:

Several projects of reactor experiment & strong world momentumFirst generation : sensitivity sin2(2θ13)~0.02-0.03 - Rate + Shape

Motionless detectors: Double-Chooz (funded in France), KASKAMovabledetectors: Daya-bay, Braidwood

Second generation : sensitivity sin2(2θ13)103 GWth.tons.years):Motionless detectors: Angra

)()()2sin(

1)2sin(

)sin(1.0)()()()(

2/11313

syststatNPP

PPA

ee

eecp ±±∝→−→

→−→=

θθδ

νννννννν

µµ

µµ