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Jelena Mari čić Drexel University On behalf of the Double Chooz Collaboration

The Quest for θ 13 with the Double Chooz Detector. Jelena Mari čić Drexel University On behalf of the Double Chooz Collaboration. Outline. Physics motivation for the Double Chooz experiment Repetitio est mater studiorum Challenges of the high precision reactor neutrino experiment

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Jelena Mari čić Drexel University On behalf of the Double Chooz Collaboration

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  1. The Quest for θ13 with the Double Chooz Detector Jelena Maričić Drexel University On behalf of the Double Chooz Collaboration

  2. Outline • Physics motivation for the Double Chooz experiment • Repetitio est mater studiorum • Challenges of the high precision reactor neutrino experiment • Detector overview • Future prospects J. Maricic-Double Chooz

  3. Neutrino oscillations (ne,nm,nt)T = U (n1,n2,n3)T U=matrice PMSN : 3 angles,1cp violation phase (+2 mass differences) solar n leptonic CP phase d atmospheric n θ23 ~ 45 CHOOZ q13< 13 θ12 ~ 32 *CP violation is responsible for matter- antimatterasymmetry Leptons = e, , , e, ,  Leptonic CP violation phase  completely unknown Θ13 small  directly affects prospects of measuring leptonic CP violation phase The future quest for 13 Accelerators Reactors J. Maricic-Double Chooz

  4. 13& Reactor Experiments • <E> ~ a few MeV  only disappearance experiments sin2(213) measurement independent of -CP • 1-P(e e) = sin2(213)sin2(m231L/4E) + O(m221/m231) •  weak dependence in m221 • a few MeV e + short baselines  negligible matter effects (O[10-4] ) •  sin2(213) measurement independent of sign(m213) 13 & Accelerator Experiments Appearance probability :  dependences in sin(223), sin(23), sign(m231), -CP phase in [0,2] J. Maricic-Double Chooz

  5. How well can We Measure CP Violation? Hopeless without beam upgrade Even with beam upgrade chance <15% If sin22θ13 < 0.025 NOvA and T2K will not start before 2011. Courtesy of R. Svoboda It would be great to know ASAP if the value of θ13 is large or small J. Maricic-Double Chooz

  6. e e (disappearance experiment) Pth= 8.4 GWth, L = 1.050 km, M = 5 toverburden: 300 mwe Best current constraint: CHOOZ R = 1.01  2.8%(stat)2.7%(syst) World best constraint! @m2atm = 2 10-3 eV2 sin2(2θ13) < 0.2 (90% C.L) e  x M. Apollonio et. al., Eur.Phys.J. C27 (2003) 331-374 J. Maricic-Double Chooz

  7. Challenges of the High Precision Reactor Neutrino Experiment J. Maricic-Double Chooz

  8. Reactor Neutrino Detection Signature • Reactors are tremendous sources of neutrinos: P = 8GW  N~1021s-1 Neutrino detection: +  Gd Tiny Distinctive two-step signature: -prompt event Photons from e+ annihilation Ee = E+ 0.8 MeV + O(Ee/mn) -delayed event Photons from n capture on dedicated nuclei (Gd) t ~ 30 s E ~ 8 MeV J. Maricic-Double Chooz

  9. Expected Backgrounds in Reactor Neutrino Experiments Accidental bkg: • e+-like signal: radioactivity from materials, PMTs, surrounding rock Rate=Re • n signal: n from cosmic  spallation, thermalized in detector and captured on Gd (Rn)  Accidental coincidence Rate = Re x Rn x Δt Correlated bkg: • fast n (by cosmic ) recoil on p (low energy) and captured on Gd • long-lived (9Li, 8He) -decaying isotopes induced by  Bkg reduction and knowledge is critical for oscillation measurement ! J. Maricic-Double Chooz

  10. CHOOZ Double-Chooz Target volume 5,55 m3 10,2 m3 Target composition 6,77 1028 H/m3 6,82 1028 H/m3 Data taking period Few months 3-5 years Event rate 2700 Far: 60 000/3 y Near: ~3 106/3 y Statistical error 2,7% 0,5% How Can We Improve Limit on θ13 Based on Experience with CHOOZ ? CHOOZ : Rosc = 1.01 ± 2.8% (stat) ±2.7% (syst) • Statistics • More powerful reactor (multi-core) • Larger detection volume • Longer exposure • Experimental error:  flux and cross-section uncertainty • Multi-detector • Identical detectors to reduce inter-detector systematics (goal: towards σrelative~0,6%) • Background • Improve detector design larger S/B • Increase overburden • Improve bkg knowledge by direct measurement • subtraction error<1%  Luminosity increase L = t x P(GW) x Np J. Maricic-Double Chooz

  11. 13 at Reactors: The Double Chooz a New Experimental Concept 1,050 m 280 m Far Detector Reactor Near Detector ne? ne 2 13 P(ee) ~ 1 - sin2 213 sin2(m213L/4E)+… J. Maricic-Double Chooz

  12. 13 at Reactors Two independent sets of information: Normalisation + Spectrum distortion m2atm = 2.0 10-3 eV2 sin2(213)=0.04 sin2(213)=0.1 sin2(213)=0.2 Events/200 KeV/3 years E (MeV) Far Detector: ~ 60 000events/3y -Reactor efficiency: 80% -Detector efficiency: 80% E (MeV) Near Detector: ~ 3 106 events/3y -Reactor efficiency: 80% -Detector efficiency: 80% -Dead time: 50% J. Maricic-Double Chooz

  13. Detector Overview J. Maricic-Double Chooz

  14. The Chooz Site ~1000 ev/day ~70 ev/day 80 m.w.e. 300 m.w.e. Chooz-B reactors J. Maricic-Double Chooz

  15. Reactor-Induced Systematics Distance ratio exactly cancels reactor thermal power uncertainty. 1114.6m 997.9m 260.3m Uncertainty due to solid angle is 0.06% 290.7m J. Maricic-Double Chooz

  16. 511 keV 511 keV e+ e p Gd n  ~ 8 MeV The detector design Muon Outer-VETO: 7 m • -target: 80% dodecane + 20% PXE + 0.1% Gd Volume for -interaction -catcher: 80% dodecane + 20% PXE Extra-volume for -interaction 7m Acrylic vessels  «hardware» definition of fiducial volume Non-scintillating buffer: same liquid (+ quencher?) Isolate PMTs from target area Muon Inner-VETO: scintillating oil Shielding: steel 17 cm: >7  Improved background reduction PMT support structure: steel tank, optical insulation target/veto J. Maricic-Double Chooz

  17. The detectors AcrylicTarget vessel (Inner radius =1,15m H = 2,474m t = 8mm) Acrylic Gamma catcher vessel (Inner radius= 1,696m Inner H = 3,55 m t = 12mm) LS LS + 0,1%Gd Stainless steel Buffer (Inner radius = 2,758m Inner H = 5,674m t = 3mm) Muons VETO (shield) Inner radius = 3,471m Thickness = 200mm J. Maricic-Double Chooz

  18. Technological Challenges J. Maricic-Double Chooz

  19. What is the State of the Art? • Chooz had a 1.6% absolute detector systematic uncertainty, the best to date. Total uncertainty 2.7% • Bugey is the only experiment that has tried to build identical detectors. Result was 2.0% relative error. 5.0% total. • Double Choozgoal is 0.6% relative uncertainty. J. Maricic-Double Chooz

  20. How will We Do This? • We will use a physical tank for the fiducial volume instead of fitted vertex, unlike KamLAND, which has 4.7% uncertainty doing this (before 4p system) • We will control detector temperature at Near and Far Detector with active heating. • We will remix scintillator when starting Near Detector, or else throwaway first batch. • We will control the magnetic field inside detector and have developed a way to demagnetize the steel components. All PMT’s will have individual  metal shields. J. Maricic-Double Chooz

  21. …And • We have developed systems to measure the mass of target poured into each detector (0.2%) • We have considered variation of g, effects of finite size core and detector on distance (<0.1%) • We have considered effects of different depth for Near and Far (<0.1%) • Swapcalibrationsystems, which can be done easily, cheaply, and at the same time J. Maricic-Double Chooz

  22. Scintillator Stability Studies • Solvant: 20% PXE – 80% Dodecane • Gd loading: being developed @MPIK & LNGS • 0.1% Gd loading • Two formulations under study: • Gd-CBX Based on Carboxilic acids (+stabilizers) • Gd-Acac & Gd-Dmp Beta Dikitonate • Long term Stability • LY ~7000 ph/MeV: 6 g/l ppo + 50 mg/l Bis-MSB • Attenuation length: a few meters at 420 nm 3+Gd Long term stability is essential for near-far detector comparison Results on the different formulation now available on 2 years’ tests. LY~8000 /MeV L = 5-10 m Validation through optical monitoring of the liquids. J. Maricic-Double Chooz

  23. A 1/5 prototype Last stage for the validation of the technical choices for vessels construction, material compatibility, filling, and the integration of the detector at the Chooz site Total of 2000 l of oil Filling 13/12/2005 Stable in the detector • Inner Target: 120 l : 20%PXE+80%dodecane+0.1%Gd • Gamma Catcher: 220 l : 20%PXE+80%dodecane All teflon filling system J. Maricic-Double Chooz

  24. μ μ μ capture n from  capture Recoil p Gd Gd Recoil p n capture on Gd Spallation fast neutron Muon simulation Measured angular distributions are well reproduced • Knowledge of  fluxes at underground  experiments is essential for a precise determination of the induced backgrounds: spallation n’s, radioactive nuclei, bremsstrahlung ’s… • A measurement of  distribution was performed at Chooz in 1995. They were correctly parametrized, but no detailed information on the energy spectrum was available. Energy spectrum Detailed simulation with MUSIC + rock composition + hill profile: Phys.Rev.D74: 053007,2006 [hep-ph/0604078] J. Maricic-Double Chooz

  25. e+ e p Gd n Relative Normalization: Analysis • @Chooz: 1.5% syst. err. - 7 analysis cuts - Efficiency ~70% • Goal Double-Chooz: ~0.3% syst. err. - 2 to 3 analysis cuts Selection cuts • - neutron energy • (- distance e+ - n ) • [level of accidentals] • - t (e+ - n) e+ n t J. Maricic-Double Chooz

  26. Level 1 trigger (analog sum above 0.5 MeV) FIFO Level 2 trigger (2 coincident Level 1 triggers) Event builder (-like -tagged) Storage Data Acquisition System Zero dead-time DAQ ~ 400 (target) + 100 (veto) PMTs Flash-ADC CAEN N(V)1726 developed by APC-Paris + CAEN • 4 channels • Wave-form sampling @ 500MHz • 8-bit resolution (few PEs/ch for ν evts) • Continuous digitising with zero deadtime (if DAQ sustains trigger rate) • 2s waveform data recording NIM version available, under test @APC Several components of VME version ready J. Maricic-Double Chooz

  27. Prospects with Double Chooz J. Maricic-Double Chooz

  28. Double Chooz Timeline 90% C.L. Double Chooz will improve the limit on sin2213 significantly and soon! • Data Taking • mid 2008 Far detector completion • > 1 year sin2213 > ~0.07 with far detector alone • 2009 Near detector completion • > 1 year sin2213 > 0.04 with 2 detectors • > 3 year sin2213 > 0.02-0.03 with 2 detectors 2003 2004 2005 2006 2007 2008 2009… …2011 Site Prop. design+test simulation Construction Data taking and analysis J. Maricic-Double Chooz

  29. group of ~120 scientists from 8 countries France, U.S., Germany, Spain, Russia, Italy, Brazil, U.K., Japan Very Experienced: Chooz, Bugey, KamLAND, Super-Kamiokande, SNO,Borexino The Double Chooz Collaboration Spokesperson: H. de Kerret (APC) Over 100 members in the collaboration J. Maricic-Double Chooz

  30. Conclusion and Summary • Double Chooz is a significant technological challenge. • There has been a huge amount of work done to control systematics in order to minimize technological and cost risk. Backgrounds are under control. It is a huge advantage to have data from a previous neutrino experiment at the same site. • The collaboration is extremely experienced, with many members having done several previous reactor experiments. • The schedule is conservative and realistic. • Double Chooz will achieve an unprecedented high precision measurement for a reactor neutrino experiment. • Great gain in knowledge that will in prospect help get tighter constraints on geo-neutrino measurements with future detectors. J. Maricic-Double Chooz

  31. J. Maricic-Double Chooz

  32. Complementarity with Superbeams 3 discovery potential 3 sensitivity (no signal) For a fair comparison of Reactor & Beam programs, both information should always be quoted together! J. Maricic-Double Chooz

  33. Systematics J. Maricic-Double Chooz

  34. On the median 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 ~250 m ~10% 3 years data taking J. Maricic-Double Chooz

  35. Phototubes baseline • 10‘‘ Ultra low background tubes • 365 PMTs • 13 % coverage • Energy resolution goal: 7 % at 1 MeV • Current work: • PMT selection (radiopurity) • ETL 9354KB ? • Hamamatsu R5912 ? • Photonis: XP1806 ? • Angular sensitivity, Concentrators? • Tilting tube options • Cabling & Tightness • B fields shielding J. Maricic-Double Chooz

  36. e+ e p Gd n Relative Normalization: Analysis • @Chooz: 1.5% syst. err. - 7 analysis cuts - Efficiency ~70% • Goal Double-Chooz: ~0.3% syst. err. - 2 to 3 analysis cuts Selection cuts • - neutron energy • (- distance e+ - n ) [level of accidentals] • - t (e+ - n) e+ n t J. Maricic-Double Chooz

  37. How well can they resolve the mass ordering problem? Phase 1 has no chance of even 2s if sin22q13 < 0.025 Billion $ upgrade J. Maricic-Double Chooz

  38. Fit Using Extended Spectrum Fitted flat backround rate <8 MeV is 254/114 days =2.23(0.14) d-1 Consistent with published paper Fit Range flat 9-Li J. Maricic-Double Chooz

  39. Role of θ13 in Neutrino Oscillations (ne,nm,nt)T = U (n1,n2,n3)T s13 sin θ13 Chooz experiment R = 1.01  2.8%(stat)2.7%(syst) U=matrice PMNS : 3 angles,1CP violation phase (+2 mass differences) Only the upper limit on the value of angle θ13 has been set! Value of θ13directly influences prospects of measuring CP violation phase in the weak sector! World best constraint: CHOOZ experiment! (e  e disappearance exp) @m2atm = 2 10-3 eV2 sin2(2θ13) < 0.2 (90% C.L) e  x M. Apollonio et. al., Eur.Phys.J. C27 (2003) 331-374 Accelerators The future quest for θ13 Reactors J. Maricic-Double Chooz

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