Summary of the workshop on Future Low-Energy Neutrino Experiments TUM, Munich, October 9-11, 2003

Thierry LasserreCEA/Saclay, CERN, 20/11/2003

One nuclear plant & two detectors

Nuclear reactor

1,2 core(s) ON/OFF : ok 4 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

e e,,

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

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

Groups involved in discussions

France :

•PCC, Collège de France & APC (Chooz, LENS, Borexino)

•CEA/Saclay (LENS)

Germany :

•MPI fuer Kernphysik, Heidelberg (Borexino, LENS Gd scintillator)

•TUM, Munich (Borexino)

•Tubingen University (Borexino)

US :•Columbia University•Argonne National Laboratory•Berkeley Laboratory•The University of Chicago•The University of Alabama•Caltech•Stanford University• etc …

Italy :•INFN Bologna

Japan : •Tokyo Metropolitan University•Tohoku University

Russia :•Kurchatov Institute

sorry for the groups I have omitted …

Session I: Motivation & Phenomenology

09:40 M. Lindner, TUM, "Theoretical reasons / motivation for sin^2(2theta_13) of the order 0.01" (15'+5')

10:00 M. Tanimoto, Niigata University, "Theoretical considerations & prediction of sin^2(2theta_13) in Texture Zeros" (15'+5')

10:20 V. Sinev, Kurchatov Institute, "Searches for theta13 and sterile neutrinos at reactors" (20'+5')

11:15 S. Choubey, SISSA, Trieste, "Future measurements of theta12 with reactors" (25'+5')

11:45 W. Winter, TUM, "Comparison and synergy of reactor measurements with beam experiments" (30'+5')

14:00C. Hagner, Virginia Polytechnic Inst. and State Univ., "Review of accelerator neutrinos experiments potentials for theta13" (30'+5')

Session II: Experimental sites

14:35 F. Suekane, Tohoku University, "Situation in Japan" (45')

15:20 J. Link, Columbia University, "Situation in US-I: US east/midwest efforts, status, and comments" (30')

15:50 K. Heeger, LBL, Berkeley, "Situation in US-II: The Diablo Canyon site" (45')

17:05 T. Lasserre, Saclay, "Situation in France" (45')

17:50 D. Reyna, ANL, "Situation in Taiwan" (15')

18:05 D. Reyna, ANL, "Situation in Brazil" (25')

18:30 Yu. Kozlov, Kurchatov, "Comments on the situation in Russia" (10')

Session III: Systematic errors & Backgrounds

09:30 T. Schwetz, TUM, "Principal issues of the reactor setup (statistics, near/far detector distance scaling, systematics)" (25'+5')

10:00 H. de Kerret, PCC College de France & APC, "Systematic errors and backgrounds for a Double-CHOOZ experiment" (40'+5')

11:15 G. Mention, PCC & APC, "Systematic errors & sensitivity to sin2(2theta13)" (25'+5')

11:45 O. Yasuda, Tokyo Metropolitan Univ., "Sensitivity of experiments with multi reactors and multi detectors" (25'+5')

12:15 V. Sinev, Kurchatov Institute, Moscow, "Comment on time dependent corrections to the ILL reconstructed spectra" (10'+5')

12:30 G. Horton-Smith, Caltech, "Quashing Backgrounds" (25'+5')

09:30 H. Minakata, Tokyo Metropolitan Univ., "Comments on reactor-LBL complementarity"

09:40 M. Goodman, ANL, "Status of the White Paper"

10:00 Discussion

Session IV: Experimental issues

14:30 J. Link, Columbia, "On cost/benefit analyses for spherical vs. cylindrical detectors and other issues" (25'+5')

15:00 C. Laughton, Fermilab, "Construction issues, tunnelling" (25'+5')

15:30 L. Inzhechik, Kurchatov Institute, Moscow, "The Russian technologies of isotopes production for neutrino experiment: 1.Stable isotopes for neutrino detectors. 2. Artificial isotope neutrino sources for calibration." (20'+5')

15:55 F. Hartmann, MPI f. Kernphysik, Heidelberg, "Low-Level Scintillators and Gadolinium" (25'+5')

16:25 C. Buck, MPI f. Kernphysik, Heidelberg, "Metal Diketones Gadolinium scintillator" (15'+5')

Session V: Discussion of specific proposals (site+detector+funding) + Publications

Detector size scale

Borexino300 t

KamLAND1000 t

Reactor/13

Example ~20 t( 5 50 t)

CHOOZ5 t

DoubleCHOOZ10-15 t !

X 2

90% C.L. sensitivity if sin2(213)=0

Reactor1 (0.5 km, 2.3 km): ~13 tonsPXE x 10 GW x 3 years sin2(213)<~0.02, 90% C.LReactor2 (0.5 km, 2.3 km): ~270 tonsPXE x 10 GW x 3 years sin2(213)<~0.01, 90% C.L

JHF

Huber, Lindner, S

chwetz &

Winter: hep-ph/0303232

G. M

en tion & T. L.

σbkg

σbkg σbkg

reactor 1 (2 RNU) reactor 2 (40 RNU)

1%

0.1%

@m2=2.0 10-3 eV2

RNU = Reactor Neutrino Unit : 1 RNU = 1031 free H GWth year

Forthcoming LBL & sin2(213)

Huber, Lindner, Schwetz & Winter (Theory group, TUM)

CHOOZ-I90% C.L

Huber, Lindner, Schwetz & Winter, (Theory Group, TUM)

Next generation LBL & sin2(213)

CHOOZ-I90% C.L

Which site for the experiment ?

Diablo Canyon

Byron

Angra

PenlyChoozCruas

Krasnoyarsk

Taiwan

Kashiwasaki

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

Which site for the experiment …

Diablo Canyon

CHOOZ

Kashiwasaki

The Diablo Canyon site (US)

600-800 mwe

Close to San Francisco (500 km), California. Leader Group: LBNL Two cores (2 x 3.1 GWth) 3 detectors : D1~300m , D2 ~ 0.8 – 1 km , D3 ~ 2 – 3 km Horizontal tunnel >1.5 km with 300 800 mwe overburden Status: negotiation with the power plant underway (permit, safety , ecology …)

Partial approval from PG&E to proceed with geological studiesTunnel + labs + 2 movable detectors (50-100 tons) to be constructed simultaneously Data taking end 2007 ? Cost ~ 50 M$ sin2(213)<0.01-0.02 @90% C.L

The Kashiwasaki site (Japan) Kashiwasaki power plant: 24.3 GWth 7 cores 2 near detectors needed !

Leading group: Tohoku Univ. (Suekane_san & Inoue_san)

The Kashiwasaki site (Japan)

Kashiwasaki power plant : 24.3 GWth 7 cores 2 near detectors needed ! D1~300-400 m , D2 = 1.3 km 3 identical detector of ~8 tons 3 shafts (12 M$, 15 months)

Near detectors @100 mwe Far detectors @500 mwe

Data taking ~2007-2008 – Cost <20 M$

Scheme of one shaft

Sensitivity (3 years): sin2(213)<0.026 @90% C.L

The Chooz site, Ardennes, France

… Double-CH1313Z …

The Chooz site

Near site: D~100-200 m, overburden 50-80 mweFar site: D~1.1 km, overburden 300 mwe [former experimental hall]

Type PWRCores 2Power 8.4 GWth

Couplage 1996/1997(%, in to

2000)66, 57

Constructeur

Framatome

Opérateur EDF

2x11.5 tons, D1=100-200m, D2=1050m. Sensitivity: 3 years sin2(213) < ~0.03

CHOOZ-Far… ready to be used again!

CHOOZ-Far detector (12.7m3 fiducial, preliminary)

7 m

3.5 m

CHOOZ-I pit

CHOOZ-Near

250 m

125 m

A few locations under study, but enough space in any case

CHOOZ-Near new Laboratory

~5- 15 m

Dense material

~10-15 m

Other possibility: bloc of concrete (d~2.4) piled up !

Status of the discussions with EDF

CHOOZ site has been secured. -Strong support for the CHOOZ nuclear plant

Far site: 1.1 km & 300 mwe-Existing laboratory-Available (7x7 m tank of CHOOZ-I)

Near site: 100-200 m-Underground detector + man-made overburden-Feasibility confirmed by the power plant staff-50 to 80 mwe required-Civil engineering study will start soon (done & financed by EDF )

The experimental challenge

systematics Error type CHOOZ FutureSim.MC

2 identical detectorLow backgrounds

Reactor

Cross section 1.9% 0Thermal power 0.7% O(0.1%)

E/Fission 0.6% 0 2.1% O(0.1%)

Detector

Scint. Density 0.3% 0.3% O(0.1%)Target volume 0.3% 0.3% O(0.1%)

% H 1.2% 1.2% O(0.1%) « Spill in/out » effect 1.0% 1.0% X O(0.1%)

2.5% <2.5% O(0.1%)Sélection cuts

Ee+<8 Mev6<En (MeV)<12 de+-n < 100 cm

2<capture n<100s

n multiplicité =1

(tot>70%)

Ee+ threshold 0.8% 0 0 n capture 1.0% <1.0% X O(0.1%)

En 0.4% 0.4% O(0.1%) – calibration Distance (e+-n) 0.3% 0. 0

t (e+-n) 0.4% <0.4% X O(0.1%) n multiplicité 0.5% O(0.1%) O(0.1%)

1.5% <1.1% O(0.1%) ?

Relative error between Near/Far detector < 0.8% seems possible [still under study]

Sensitivity to sin2(213)

#DNear 0.1 km#NumberOfFreeProtonsNear 1.8944e+29 (11.5 tons PXE)#DFar 1.05 km#NumberOfFreeProtonsFar 3.7888e+29 (11.5 tons PXE)

#Global normalisation Fit is [ON ] with an error of 2%#Relative normalisation Fit of Near/Far Detector is [ON ] with an error of 0.06%#Shape Error Fit is [ON ] with an error of 2%

σbkg: [near] = 1% [far] = 0.5% σbkg: [near] = 1% [far] = 1% σbkg: [near] = 2% [far] = 1%

years

110.75

21.5

32.25

4 (pure PXE)3.0 (PXE/PC + mineral oil)

@m

2 atm=2

.0 1

0-3

eV2

sin2(213) @90% C.L

Support for the EDF power company to do a 2nd experiment @CHOOZReactor potential @CHOOZ: sin2(213)<~0.03, 90% C.L. (m2 = 2.0 10-3 eV2)Current limint: CHOOZ : sin2(213)<0.2 discovery potential !

Technology / design well known (Chooz-I, Borexino, KamLAND, …) few R&D needed : Gd loading (stability) + material compatibility R&D in Saclay : material compatibility + mechanical constraint + scint. test

Case under study: French target vessels & German scintillator (MPIK)

Experiment cost, Double-CHOOZ case: 2 x ~15 tons, cost detectors <~10 Meuros. (+ Civil engineering)

Our Goal @CHOOZ: Construction starts in 2005 (+ civil engineering ) Start data taking in 2007-2008

Summary & outlook @Double-CHOOZ

2003 2004 2005 2006 2007 2008 2009

Site Data takingProp. Construction ?

year

design

< sin2(213) < ~0.04 < sin2(213) < 0.025-003

Construction ?