Jaime Dawson, APC. Double Chooz

Transcription

1 Jaime Dawson, APC Double Chooz

2 DC Collaboration France: APC Paris, CEA/Dapnia Saclay, Subatech Nantes, IPHC Strasbourg Germany: Aachen, MPIK Heidelberg, TU München, EKU Tübingen, Hamburg Spain: CIEMAT Madrid UK: Sussex Japan: HIT, Kobe, MUE, Niigata, TGU, TIT, TMU, Tohoku Russia: RAS, RRC Kurchatov Institute USA: Alabama, ANL, Chicago, Columbia, Drexel, Illinois, Kansas, LLNL, LSU, Notre Dame, Sandia, Tennessee, UCD Brazil: CBPF, UNICAMP Spokesperson: Herve de Kerret June

3 Contents Brief reminder Θ13 current knowledge Reactor experiments Double Chooz concept Improvements on Chooz Neutrino signals and backgrounds Double Chooz detectors Double Chooz status Sensitivity Conclusion 3

4 Θ13 current knowledge Maltoni and Schwetz, arxiv: global: sin2(2θ13) < 0.13 (90%) sin2(θ13) < (90%) Dominated by Chooz [M.Apollonio et al, Eur. Phys. J. C27 (2003) 331] 4

5 Reactor Θ13 Experiments Disappearance of anti-neutrinos (independent of δcp and sign of Δm31, weak dependence of Δm21) ~MeV signals, short distances (no matter effects) But, limited knowledge of processes inside reactor exaggerated FAR NEAR 5

6 Concept 2 'identical' detectors Near 410 m 115 m.w.e ~500 ν/day Far 1050 m 300 m.w.e ~70 ν/day Systematics on reactor power, neutrino spectrum, cross-section insignificant for a relative measurement Chooz-B 2 x 4.27GWh 6

7 Improvements on Chooz Chooz : R = 1.01 ± 2.8% (stat) ± 2.7% (syst) Statistical Large Volume m -> 10.3m 3 Run Time ~months -> 3-5 yrs Number of Events > 60,000 (far in 3 yrs) Systematic Reactor Detector Analysis < 0.6% 0.4 % 7

8 Neutrino Signal Detect anti-neutrinos via inverse beta decay p + ν n + e+ In Gd- loaded scintillator e+ signal 1-8MeV e+ e- annihilation(2 x 511 kev) Evis = Eν (Mn-Mp)+me Delayed neutron capture on Gd ~30 μs ~ 8 MeV (>80%) H ~200 μs 2.2 MeV 8

9 Backgrounds Our signal is a positron followed by a neutron capture (2 triggers) Accidental Accidenta Dominant source of accidentals - Radioactivity (from PMT) Solution - we aim for a singles rate of less than 5/s above 0.7 MeV Correlated Li-9 and He-8 long lived Fast neutrons Stringent radiopurity constraints Cartoon Cosmogenics (β-neutron) Proton Recoil (positron-like signal) followed by neutron capture Caused by muons! Crossing Missing Stopping Want Signal/Background > 50 9

10 The Detectors Outer Muon Veto Inner Veto Vessel 78 8 PMTs scintillator 15 cm demagnetized steel (far) Gamma Catcher (acrylic) Buffer Vessel PMTs NON-scintillating mineral oil Target 10.3m3 Gdloaded Scintillator (acrylic) 10

11 The Laboratories Outer Muon Veto Plastic scintillator strips with x,y positioning Electronics Glove Boxes and Calibration systems 11

12 Muon Tracking Outer Veto Tag near miss muons Entry point of any muon Inner Veto Efficient tag of muons and secondaries Track muon Muon Electronics Attenuated output of Inner Detector PMTs Track muon Use all 3! 12

13 Inner Veto Efficient tag of cosmic ray muons and fast neutrons LAB and tetradecane, 50 cm thickness 78 8 PMTs (encapsulated IMB tubes) Reflective walls (painted and foil) Completed 13

14 Buffer Vessel Pipes for PMT cables Being installed now! (started today) Stainless steel 3mm thick Inner Height: 5674mm Inner Diameter: 5516mm Will contain 110m3 of mineral oil PMTs to be attached to walls 14

15 Filling and wire source tubes Acrylics Gamma catcher 12 mm thick acrylic Inner Height: 3550 mm Inner Diameter: 3392 mm Will contain 22.3m3 of scintillator (un-doped) Target 8 mm thick acrylic Inner Height: 2458 mm Inner Diameter: 2300 mm Will contain 10.3m3 of Gd-doped scintillator (1 g/l) To be installed in June

16 Photomultipliers (Inner Detector) Hamamatsu For Neutrino Signals Attenuated signals for muon electronics 15% coverage with '' PMTs PMTs are angled to improve light collection uniformity Aim for 7% resolution at 1 MeV Low background version Extensive testing in Japan and Germany DONE Installation May

17 Waveform Digitisers 500 MHz 8-bit flash ADC (developed with Caen V1721) Dead-time-less (for our expected event rate) In-house firmware allows choice of event size based on Info from trigger Time between consecutive events More data will be taken for the most interesting events 17

18 Gd-doped Liquid Scintillator Stability tests reassuring 100kg Gd salt No change seen over ~700 days Scintillator ingredients for both detectors ready to be mixed (MPIK) Mixing in one batch Exact proportions for both detectors (H, Gd) 18

19 Background Comparison hep-ex/ estimates with "old" near detector location = conservative (with new location: Nv/2, Nμ/3) Signal/Bkg >50 19

20 Systematics: Detector Chooz Double Chooz 20

21 Systematics: Analysis Lower threshold (see all of positron spectrum) Target Acrylic vessel (no fiducial volume cut) e n * * * t * Easier to control near vs far than absolute 21

22 Status: Near Lab Geological survey done Neutrino Lab Finalization of access tunnel + lab excavation design civil engineering to be completed by mid >45 m rock overburden 155 m of gallery (12%) Liquid Handling and Storage Building Detector to be integrated by end of

23 Status: Far Detector Lab for the original Chooz experiment 23

24 Status: Far Detector IV PMTs installed (Feb) 24

25 Status: Far Detector Buffer Vessel during construction (at company) Currently being lowered into place and welded. Started today!! 25

26 Scintillator Liquid Storage and Handling (Oct 08) 26

27 Sensitivity First phase just far detector Second phase both detectors σpwr=2.0% σrel=0.6% σspe=2.0% Provided by Mauro Mezzetto 27

28 Conclusion NOW : far detector construction End of 2009 : far detector running 2011 : near detector installation 2013: reach target sensitivity sin22θ13~0.03 (for Δm231=2.5x10-3 ev2) 28

29 backups 29

30 Complementary to Beam experiments Example of Double Chooz results compared to T2K Assume full power for T2K 2 years of 2 detector (DC) Full =90%, dashed 3σ No dependence on δcp (reactor) 30

31 Radioactive Contamination Levels 31

32 2% 1% 3% 0.6% 0.4% 1% 2% x0 0.8% 3% x2 G.Mention, Th.Lasserre Total systematics: <~ 0.6% Statistics: neutrino Far Detector 32

33 Near detector location Uncorrelated fluctuations included Relative Error : 0.6% Spectral shape uncertainty 2% m2 known at 20% Power flucutation of each core: 3% Available and suitable area On the median ~400 m ~10% 3 years data taking Spent fuel effect under study kopeikin and al.