Reactor antineutrino. Th. Lasserre Saclay. Neutrino geo-sciences 2010 LNGS, October 06 th 2010

Transcription

1 Reactor antineutrino Th. Lasserre Saclay Neutrino geo-sciences 2010 LNGS, October 06 th 2010

2 Neutrino Mass and Mixing Neutrino: spin ½, neutral, left handed chirality (~helicity), σ~10-43 cm 2 (reactor-ν) For 10 yrs we know neutrinos have tiny masses and mix: 0.04 ev<m ν < ~1 ev Two views on W decay: l + l + W ν l Neutrino of flavor l l=e, μ, τ W U li * ν i Neutrino of definite mass m i i=1, 2, 3 PMNS mixing matrix U relates mass & flavor bases: ν i > = Σ U αi ν α > First compelling evidence of physics Beyond the Standard Model T. Lasserre 09/11/2009 2

3 s U = c 23 s 23 0 s 23 c 23 Neutrino Oscillation formalism P(ν x ν x) =1 sin 2 ( 2θ i )sin 1.27 Δm i Atmospheric Cross-Mixing Solar Majorana CP phases c 13 0 s 13 e iδ s 13 e iδ 0 c 13 2 (ev 2 )L (m) E (MeV) c 12 s 12 0 e iα 1 /2 0 0 s 12 c e iα 2 / θ 23 : atm. mixing angle θ 13 c ij cos θ ij, s ij sin θ ij θ 12 δ Dirac CP violating phase : solar mixing angle 2 Majorana phases (L violating processes) 13 3 masses m 1, m 2, m 3 : 3-flavour effects are suppressed because : 3

4 What are the masses of the mass eigenstates ν i? Open questions ν 3 (Mass) 2 0 ν 2 1 Δm 2 atm? Δm 2 sol ν flavor change β decay, ββ0ν decay, Cosmology Is the spectral pattern or? ( ) ν behavior in earth matter, ββ0ν Is there any conserved Lepton Number (Dirac or Majorana neutrino)? ββ0ν What are the angles of the leptonic mixing matrix? Do the behavior of ν violate CP? Is leptonic CP responsible for the matter-antimatter asymmetry? Leptogenesis? ν flavor change 4

5 Reactor neutrinos Particle physicists are routinely used to detect antineutrinos though neutrino detection is particularly difficult A commercial nuclear station emits ~10 21 neutrinos per second A detector of 1 m 3 at 25 m from a 3 GW core sees ~5,000 ν/d A detector of 1000 m 3 at 800 km from a 100 x 3 GW cores detects ~0,5 ν/d Fuel evolution (burnup) Reactor operation: 1 kg 235 U is burned & 0.2 kg 239,241 Pu produced U and Pu have a slightly different rate/spectrum neutrino emission The neutrino count rate is a simple function of the thermal power The neutrino rate & energy spectrum is connected to Fuel Evolution Th. Lasserre 24/04/2009 5

6 MeV Reactor Neutrinos Electron antineutrinos Emitted through Decays of Fission Products Fissions of: 235 U, 238 U, 239 Pu, 241 Pu Neutrino Luminosity γ : reactor constant k : burn up dependent correction up to 10% t 0 : ~3.5% 235 U, 96.5% 238 U T. Lasserre 09/11/ < N

7 Reactor-ν flux prediction How to predict the neutrino flux from nuclear cores? Ratio Beg/End Fuel Cycle Goal 1: Time evolution of nuclear fuel (fissile elements, 235,238 U & 239,241 Pu) Inputs: initial fuel and P th (t) + nuclear core evolution code Chooz 2 x N4 205 fuel assemblies Goal 2: ν spectrum of each nucleus involved (from nuclear databases) Inputs: nuclear databases, theory of β-decay + models (750 nuclei, 10 4 β- branches) Flux know with a 2% syst. uncertainty (see after) T. Lasserre 26/05/2008 7

8 A single beta decay branch: - depends on: BR, end point, Z, R, spin-parity - Energy conservation: E e + E ν = Q From e - to anti-ν e spectrum A Z X A Z+1 Y + e + n e e - spectra from fission products have been measured (but 238 U) neutrino spectra are computed from electron spectra Ratio Beg/End Fuel Cycle Conversion method (Schreckenbach) T. Lasserre 26/05/2008 8

9 Lhuillier/Mueller ν-spectra (Saclay) Starting from Schreckenbach e- measurement + few ten thousand beta branches measurements stored in nuclear data bases A new ab-initio conversion method (T. Mueller Ph.D thesis) Full Error Propagation and Correlations included No free parameter Ratio Beg/End Fuel Cycle Conversion method (Schreckenbach) 3% bias (averaged) with respect to Schreckenbach s previous results To be published soon T. Lasserre 26/05/2008 9

10 The Breakthrough: neutrino oscillation KamLAND/Borexino definitely see remote reactors: - KamLAND: 1000 tons detector, Japanese reactors at 180 km (few ν/week) - Borexino: 300 tons detector, European reactors at 800 km Near Field Monitoring Geoneutrinos Nuclear test explosion Short shallow baseline Reactor neutrino experiments Far Field Monitoring KamLAND detector At 2700 m.w.e. depth Th. Lasserre 14/12/

11 Standard e - anit-neutrino Detection β inverse process: ν e + p e + + n Prompt e + signal E prompt = E ν -(M n -M p )+m e & Delayed n capture after thermalization Threshold: M n -M p + M e = 1.8 MeV Th. Lasserre 14/12/

12 Far Field (>50km)

13 Geo-Neutrinos (crust BSE) Uranium 238 : 238 U 206 Pb He + 6 e anti-ν e MeV Thorium 232 : 232 Th 208 Pb He + 4 e anti-ν e MeV Data from Mantovani et al PHYSICAL REVIEW D free H.year (2.6 MeV threshold; acc fast n Li/He 4kmwe)

14 Reactor Neutrinos 192 nuclear power stations included events per10 34 free H.year (2.6 MeV threshold; acc fast n Li/He 4kmwe)

15 Δm 2 21 & θ 12 ν 3 (Mass) 2 ν 2 ν 1 Δm sol 2 = ev 2 Δm 2 (ev 2 ) ~ L (km) / E(GeV) L~100 km & E~MeV Or MSW flavor transition ν e U ei 2 ν µ U µi 2 ν τ U τi 2

16 Reactor Experiments SNO Borexino Gallex/GNO SuperK KamLAND Experiment Baseline Size SuperK Sun tons SNO Sun 1000 tons KamLAND 150 km 1200 tons Borexino ~800 km 300 tons ν e

17 Reactor ν s: KamLAND & Borexino Goal : Measure the disappearance of anti-ν e from distant reactors with <L> ~ km Channel : ν e ν e (detected trough IBD) Detector: Liquid scintillator & PMTs few interactions/day-weeks E range: few 100 kev ~ ten s MeV KamLAND Oscillation Results Confirmation of the MSW-LMA solution m 2 =7.58±0.14 (stat) ±0.15 (syst) 10-5 ev 2 tan 2 θ 12 =0.56 ±0.08 (stat) ±0.08 (syst) Borexino data taking (<L> ~ 800 km) No spectrum distortion (no Δm 21 2 mes.) Sensitivity to sin 2 (2θ 12 )

18 Reactor Measurement of θ 12 Connecting the v 1 v 2 (solar) neutrino pair with the electron flavor Already KamLAND, Borexino, SNO+? A new dissapearance experiment located at the oscillation maximum : 1 Sensitivity (see Phys. Rev. D 71, ) Exposure: 60 GW th. Ton. Year 4% systematics, error on sin 2 (θ 12 ) : 2% (1σ) N os /N noosc No project funded but a few sites have been discussed: Sado Island (Japan), 55 km from Kashiwasaki power plant San Onofre (US), with the Hano Hano detector underwater Rustrel (500 mwe, France), Cruas (12 GW, 73 km), Tricastin (12 GW, 59 km)

19 Middle Field (1-50 km)

20 θ 13 ν 3 (Mass) 2 Δm atm 2 = ev 2 ν 2 ν 1 Δm sol 2 = ev 2 ν e U ei 2 ν µ U µi 2 ν τ U τi 2

21 Reactor Neutrino Experiments Double Chooz Daya bay Reno Experiment Baseline Size Power Channel Double Chooz 400 m / 1.1 km 10 m GW (2) Reno 350 / 1.4 km 20 m GW (6) Daya Bay 400 / 1.7 km 100 m GW (6)

22 @Reactor: Underlying Oscillation Physics 235 U + n th X + Y β decays u e - ν e + p e + + n e + d d W U ei * ν i (ν e ) (ν e ) U ei W u Reactor core Target H Simple oscillation formula depends sin 2 (2θ 13 ) & Δm atm2, weakly on Δm sol 2 MeV electron antineutrinos only disappearance experiments sin 2 (2θ 13 ) measurement independent of δ-cp MeV neutrinos + 1 km baseline negligible matter effects O[10-4 ] sin 2 (2θ 13 ) measurement independent of sign(δm 2 13) clean θ 13 information T. Lasserre 09/11/

23 The Current Central Role of θ 13 θ 13 is the last neutrino oscillation parameter to measure θ 12 & θ 23 >> θ 13 a guideline for oscillation models Improvement of mass parameters (m e, m ββ ) & astrophysical sources The θ 13 quest is an mandatory step prior searching for CP violation in the electroweak sector. Branching point around 2015: sin 2 (2θ 13 ) > 0.02 conventional neutrino beam (π µ ν, 1% contamination) sin 2 (2θ 13 ) < 0.02 neutrino factories (µ ν or A X e + ν, pure beams) Experimentally: need to connect the ν e flavour with the isolated neutrino (Δm atm2 ) L~1 km, E~MeV reactor neutrino experiments (Double Chooz, Daya Bay, Reno) Disappearance expt. ; θ 13 only clean L~1000 km, E~GeV accelerator experiments (T2K, Nova) Appearance expt. ; (θ 13, NH/IH, δ CP ) correlations & degeneracies Complementary projects (absolutely needed) T. Lasserre 09/11/

24 Improving CHOOZ: key facts Best R = 1.01 ± 2.8%(stat)±2.7%(syst) Statistical error Luminosity incerase: L = Δt x P(GW) x N Target H Target volume Target composition Data taking period Event rate Statistical error CHOOZ 5,55 m 3 6, H/m 3 Few months ,7% Double Chooz 10,3 m 3 6, H/m years Far: / Near: (3 y) 0,5% Systematic & Background errors - Two Detector Concept - Improved detector design: Lower threshold, e+ and n Efficiencies, Calibration - Lower Background: Shielding, Radiopurity Syst. error CHOOZ Double Chooz Reactor 1.9% --- Target H 0.8% 0.2% efficiency 1.5% 0.5% T. Lasserre 09/11/

25 The experimental concept for θ 13 P(ν e ν e ) = 1-sin 2 (2θ 13 )sin 2 (Δm 2 31L/4E) Lev Mikaelyan (Kurchatov, 2000) Near detector Far detector e + spectrum Far Detetector Stat. Errors ~10 21 ν e /s Δm 2 atm = ev 2 sin 2 (2θ 13 )=0.12 ν e ν e,µ,τ ν e,μ,τ Nuclear Power Station Near detector(s) Far detector(s) <500 m 1-2 km Far/Near ratio T. Lasserre 09/11/

26 Backgrounds & Signal Electron antineutrino signature through inverse beta decay ν e 511 kev 511 kev p e + Gd n Σγ ~ 8 MeV Prompt e + (1-8 MeV) Delayed n Gd-capture (8 MeV) Time correlation: τ 30 μs Space correlation: <1 m Accidental Background n Correlated Background Neutron slowing/thermalisation γ + Gd n Gd Eγ >~ 1 MeV Σγ ~ 8 MeV Σγ ~ 8 MeV T. Lasserre 09/11/

27 Double Chooz Reactor Detector 120 m.w.e. 300 m.w.e GW th

28 Double Chooz 130 physicists 35 laboratories France Germany Japan Spain U.S.A Russia Brazil U.K.

29 Th. Lasserre AAP

30 Far Site Status Liquid Storage Building Tunnel entrance Tunnel: 140 m Chooz-A Power Plant Being dismantled Neutrino Laboratory - Laboratory status: - Site of the CHOOZ experiment (14 C) - Features: - 1 km baseline ( y -1 ) mwe. (hill topology) - µ-rate: ~20 - ISO 6 Clean Room - Liquid storage building Safety files accepted by French authorities (ASN) T. Lasserre 09/11/

31 Near Site Status 100 m Neutrino Lab 85 m open air ramp 155 m of gallery DC Higgs building - - Status: - - Fully Funded (7 partners) - - Site Engineering Study Completed - - Schedule: laboratory delivery mid Features: m from nuclear cores ( y -1 ) - A 155 m tunnel to access the new lab Hill side m.w.e (almost flat topology) - µ-rate: ~250 Schiste-Gres rock T. Lasserre 09/11/

32 Electronics & DAQ Detector Design New 4-region large detector concept from Double Chooz Coll. (2003) Outer Veto: plastic scintillator strips (400 mm) ν-target: 10,3 m 3 scintillator doped with 1g/l of Gd compound in an acryclic vessel (8 mm) CEA-DSM-IRFU (thechnical coordination) γ-catcher: 22,3 m 3 scintillator in an acrylic vessel (12 mm) Buffer: 110 m 3 of mineral oil in a stainless steel vessel (3 mm) viewed by 390 PMTs Inner Veto: 90m 3 of scintillator in a steel vessel equipped with 78 PMTs Veto Vessel (10mm) & Steel Shielding (150 mm) (4 liquid densities adjusted within 0.1%) T. Lasserre 26/05/

33 Detector Interior 33

34 Detector Closing T. Lasserre 09/11/

35 Detector Commissionning First pe s signals in May 2010 (DAQ installed and operational) T. Lasserre 09/11/

36 Sensitivity (Limit) Timeline Δm 2 atm = ev 2 (20% uncertainty) σ sys =2.5% σ sys =0.6% Excluded by CHOOZ Efficiencies included 1% bin-bin uncorrelated error on background subtraction. Systematics 1Det = CHOOZ Far detector (1km) alone Both detectors 1 km & 400 m years Systematics 2Det: σ abs = 2.0% σ rel = 0.6% σ scl = 0.5% σ shp = 2.0% σ Δm2 = 20% T. Lasserre 09/11/

37 Double Chooz Status Far detector construction & intégration - 12/2010 Start of phase I : Far 1 km detector alone sin 2 (2θ 13 ) < 0.06 after 1,5 y (90% C.L.) if no-oscillation Near Lab Excavation Near Detector Integration Start of phase II : both near and far detectors sin 2 (2θ 13 ) < 0.03 after 3 y (90% C.L.) if no-oscillation

38 Daya Bay 923 m.w.e. Reactor Detector 291 m.w.e. >3 km tunnel New surface infrastructure 3 laboratory hall 8 detectors Gd-volume: 200 m m.w.e. 2.9 GW th Daya Bay nuclear power station in China

39 Status of Daya Bay Four reactor cores P=4 x 2.9 = 11.6 GW th 2 new cores for 6 GW th in Civil construction Near: 1 km tunnel + laboratory Far: 2 km tunnel + laboratory Total length: 3370 m 8x20 tons detector modules (fiducial) Near: 4x20 tons m 200 mwe Far: 4x20 tons km 1000 mwe Movable detector concept (in water pools) Expected Sensitivity 0.36% systematic error 3 years low backgrounds sin 2 (2θ 13 ) < 0.01 (90% C.L.) T.L. (Saclay) - NO-VE

40 A huge infrastructure T. Lasserre 09/11/

41 Detector status T. Lasserre 09/11/

42 Sensitivity & Milestones of Daya Bay Sensitivity in sin 2 2θ13: sin 2 2θ13 < 90% CL in 3 years of data taking with 8 detectors running simultaneously Aug 2009: Fall 2009: 2011: End 2012: Begin detector assembly Begin detector installation in experimental halls Start data taking with first near hall Start data taking with all detectors T. Lasserre 09/11/

43 RENO 2 detectors Gd-volume: 40 m m.w.e. Reactor Detector 2.73 GW th 675 m.w.e. Yong gwang nuclear power station in Korea

44 RENO Six reactor cores: P~16 GW th (ND: 90% ν s from 2 cores) Civil construction km tunnel + hall ready! Two 20 tons detectors Near: 20 tons mwe Far: 20 tons km mwe Integration on going Sensitivity 0.45% systematic error sin 2 (2θ 13 ) < ~ 0.02 (90% C.L.) T.L. (Saclay) - NO-VE Double Chooz design cut/paste

45 Near & far tunnels are completed (construction ~2009.3) by Daewoo Eng. Co. Korea T. Lasserre 09/11/

46 Status Report of RENO RENO is suitable for measuring sin 2 (2θ 13 ) > 0.02 Civil construction completed s Buffer steel containers are installed Targe PMT installation start in Dec. 09 Acrylic containers will be completed end 2009 Data taking is expected in 2011 T. Lasserre 09/11/

47 Experimental Comments New 4-region large detector concept from Double Chooz Coll. (2003) ( Concept adopted by Daya Bay and Reno BUT Double Chooz syst: 0.6% RENO sys:0.45% Daya Bay sys: 0.38% Different expected sensitivities (without det. Swaping) Double Chooz Cons: Shorter baseline Pros: 2 cores reactor OFF periods, calibration, accidental bkg Daya Bay Cons: 9 baselines / 6 nuclear cores Pros: 160 tons of active volume, opt. baseline, corr. bkg RENO Cons: Near/Far assymetric configuration, accidental bkg, calibration Pros: Infrastructure ready T. Lasserre 09/11/

48 Near Field (<< 1km)

49 The Neutrino-meter Typical scenario: Nucifer REP900 reactor P th = 3.5 GW th 850l scintillator Nucifer at 25 m from the core 2000/ day (50% eff) need >10 mwe overburden Th. Lasserre AAP

50 Nucifer Overview Thermal Power Measurement Fuel Composition Measurement 239/241 Pu 4π plastic scintillator Muon Veto (30 PMTs) distance: 7 metres 70 MW N2 blanket overburden: 10 m.w.e Osiris research reactor CEA-Saclay (1000 ν/d) 10 cm lead Light injection system (7 diodes) 2,8 m 15 cm polyethylene AAP x 8 PMTs low background 25 cm acrylics buffer Calibration pipe Target: 0.85 m 3 Gd-LS (0.5%) Stainless steel double containment vessel coated with white Teflon coating inside 50

51 Other worldwilde efforts done data taking being built RNR, PSD Th. Lasserre AAP