1. Summary of the workshop on Future Low-Energy Neutrino Experiments TUM, Munich, October 9-11, 2003 Thierry Lasserre CEA/Saclay, CERN, 20/11/2003

2. 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 D 1 = 0.1-1 km D 2 = 1-3 km e e, ,  Isotrope e flux (uranium & plutonium fission fragments) Detection tag : e + p  e + + n, ~ 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% !

3. 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 …

4. Session I: Motivation & Phenomenology 09:40M. 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') 10:20V. Sinev, Kurchatov Institute, "Searches for theta13 and sterile neutrinos at reactors" (20'+5') 11:15S. Choubey, SISSA, Trieste, "Future measurements of theta12 with reactors" (25'+5') 11:45W. Winter, TUM, "Comparison and synergy of reactor measurements with beam experiments" (30'+5') 14:00 C. Hagner, Virginia Polytechnic Inst. and State Univ., "Review of accelerator neutrinos experiments potentials for theta13" (30'+5') Session II: Experimental sites 14:35F. Suekane, Tohoku University, "Situation in Japan" (45') 15:20J. Link, Columbia University, "Situation in US-I: US east/midwest efforts, status, and comments" (30') 15:50K. Heeger, LBL, Berkeley, "Situation in US-II: The Diablo Canyon site" (45') 17:05T. Lasserre, Saclay, "Situation in France" (45') 17:50D. Reyna, ANL, "Situation in Taiwan" (15') 18:05D. Reyna, ANL, "Situation in Brazil" (25') 18:30Yu. Kozlov, Kurchatov, "Comments on the situation in Russia" (10')

5. 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') 11:15G. Mention, PCC & APC, "Systematic errors & sensitivity to sin2(2theta13)" (25'+5') 11:45O. 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') 12:30G. Horton-Smith, Caltech, "Quashing Backgrounds" (25'+5') 09:30H. Minakata, Tokyo Metropolitan Univ., "Comments on reactor-LBL complementarity" 09:40M. Goodman, ANL, "Status of the White Paper" 10:00Discussion Session IV: Experimental issues 14:30J. Link, Columbia, "On cost/benefit analyses for spherical vs. cylindrical detectors and other issues" (25'+5') 15:00C. 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') 15:55F. 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

6. Detector size scale Borexino 300 t KamLAND 1000 t Reactor/  13 Example ~20 t ( 5  50 t) CHOOZ 5 t Double CHOOZ 10-15 t ! X 2

7. 90% C.L. sensitivity if sin 2 (2  13 )=0 Reactor 1 (0.5 km, 2.3 km): ~13 tons PXE x 10 GW x 3 years  sin 2 (2  13 )<~0.02, 90% C.L Reactor 2 (0.5 km, 2.3 km): ~270 tons PXE x 10 GW x 3 years  sin 2 (2  13 )<~0.01, 90% C.L JHF Huber, Lindner, Schwetz & Winter: hep-ph/0303232 G. Men tion & T. L. σ bkg reactor 1 (2 RNU)reactor 2 (40 RNU) 1% 0.1% @  m 2 =2.0 10 -3 eV 2 RNU = Reactor Neutrino Unit : 1 RNU = 10 31 free H GW th year

8. Forthcoming LBL & sin 2 (2  13 ) Huber, Lindner, Schwetz & Winter (Theory group, TUM) CHOOZ-I 90% C.L

9. Huber, Lindner, Schwetz & Winter, (Theory Group, TUM) Next generation LBL & sin 2 (2  13 ) CHOOZ-I 90% C.L

10. Which site for the experiment ? Diablo Canyon Byron Angra Penly Chooz Cruas Krasnoyarsk Taiwan Kashiwasaki One reactor complex Two underground cavities @0.1-1 km & ~1-2 km

11. Which site for the experiment … Diablo Canyon CHOOZ Kashiwasaki

12. The Diablo Canyon site (US) 600-800 mwe  Close to San Francisco (500 km), California. Leader Group: LBNL  Two cores (2 x 3.1 GW th )  3 detectors : D 1 ~300m, D 2 ~ 0.8 – 1 km, D 3 ~ 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 studies  Tunnel + labs + 2 movable detectors (50-100 tons) to be constructed simultaneously  Data taking  end 2007 ? Cost ~ 50 M$  sin 2 (2  13 )<0.01-0.02 @90% C.L

15. The Kashiwasaki site (Japan) Kashiwasaki power plant: 24.3 GW th 7 cores  2 near detectors needed ! Leading group: Tohoku Univ. (Suekane_san & Inoue_san)

16. The Kashiwasaki site (Japan)  Kashiwasaki power plant : 24.3 GW th  7 cores  2 near detectors needed !  D 1 ~300-400 m, D 2 = 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): sin 2 (2  13 )<0.026 @90% C.L

17. The Chooz site, Ardennes, France … Double-CH  13  13 Z …

18. The Chooz site Near site: D~100-200 m, overburden 50-80 mwe Far site: D~1.1 km, overburden 300 mwe [former experimental hall] TypePWR Cores2 Power8.4 GW th Couplage1996/1997 (%, in to 2000) 66, 57 ConstructeurFramatome OpérateurEDF 2x11.5 tons, D1=100-200m, D2=1050m. Sensitivity: 3 years  sin 2 (2  13 ) < ~0.03

19. CHOOZ-Far… ready to be used again!

20. CHOOZ-Far detector (12.7m 3 fiducial, preliminary) 7 m 3.5 m CHOOZ-I pit

21. CHOOZ-Near 250 m 125 m A few locations under study, but enough space in any case

22. CHOOZ-Near new Laboratory ~5- 15 m Dense material ~10-15 m Other possibility: bloc of concrete (d~2.4) piled up !

23. 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 )

24. The experimental challenge systematicsError typeCHOOZFuture Sim. MC 2 identical detector Low backgrounds Reactor Cross section1.9%0 Thermal power0.7%O(0.1%) E/Fission0.6%0  2.1% O(0.1%) Detector Scint. Density0.3% O(0.1%) Target volume0.3% O(0.1%) % H1.2% O(0.1%) « Spill in/out » effect1.0% XO(0.1%)  2.5%<2.5%O(0.1%) Sélection cuts Ee+<8 Mev 6<En (MeV)<12 de+-n < 100 cm 2<capture n<100  s n multiplicité =1 (  tot >70%) Ee+ threshold0.8%00 n capture1.0%<1.0%XO(0.1%) En0.4%  0.4%O(0.1%) – calibration Distance (e+-n)0.3%0. 0  t (e+-n)0.4%<0.4%XO(0.1%) n multiplicité0.5%O(0.1%)  1.5%<1.1% O(0.1%) ? Relative error between Near/Far detector < 0.8% seems possible [still under study]

25. Sensitivity to sin 2 (2  13 ) #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% σ bkg : [near] = 1%[far] = 0.5% σ bkg : [near] = 1%[far] = 1% σ bkg : [near] = 2%[far] = 1% years 1 1 0.75 2 1.5 3 2.25 4(pure PXE) 3.0(PXE/PC + mineral oil) @  m 2 atm =2.0 10 -3 eV 2 sin 2 (2  13 ) @90% C.L

26. Support for the EDF power company to do a 2 nd experiment @CHOOZ Reactor potential @CHOOZ: sin 2 (2  13 )<~0.03, 90% C.L. (  m 2 = 2.0 10 -3 eV 2 ) Current limint: CHOOZ : sin 2 (2  13 )<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 200420052006200720082009 SiteData takingProp.Construction ? year design < sin 2 (2  13 ) < ~0.04 < sin 2 (2  13 ) < 0.025-003 Construction ?