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Overview of the Daya Bay experiment

Overview of the Daya Bay experiment. Yifang Wang Institute of High Energy Physics. Neutrino oscillation: PMNS matrix. If Mass eigenstates  Weak eigenstates  Neutrino oscillation Oscillation probability ： P (n1->n2)  sin 2 (1.27 D m 2 L/E). Atmospheric. crossing：CP & q 13.

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Overview of the Daya Bay experiment

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  1. Overview of the Daya Bay experiment Yifang Wang Institute of High Energy Physics

  2. Neutrino oscillation: PMNS matrix IfMass eigenstates  Weak eigenstates Neutrino oscillation Oscillation probability： P(n1->n2)  sin2(1.27Dm2L/E) Atmospheric crossing：CP & q13 solar bb decays EXO Genius CUORE NEMO Homestake Gallex SNO KamLAND Super-K K2K Minos T2K Daya Bay Double Chooz NOVA A total of 6 parameters: 2 Dm2, 3 angles, 1 phases + 2 Majorana phases

  3. Evidence of Neutrino Oscillations Unconfirmed: LSND: Dm2 ~ 0.1-10 eV2 Confirmed: Atmospheric: Dm2 ~ 210-3 eV2 Solar: Dm2 ~ 8 10-5 eV2 Values of theta12 and theta23. 2 flavor oscillation in vacuum: P(n1->n2) = sin22qsin2(1.27Dm2L/E)

  4. Current Knowledge of 13 Global fit fogli etal., hep-ph/0506083 Direct search PRD 62, 072002 Sin2(213) < 0.18 Sin2(213) < 0.09 Allowed region

  5. Importance to know q13 1）A fundamental parameter 2）important to understand the relation between leptons and quarks, in order to have a grand unified theory beyond the Standard Model 3）important to understand matter-antimatter asymmetry • If sin22q13>0.01，next generation LBL experiment for CP • If sin22q13<0.01, next generation LBL experiment for CP ??? 4）provide direction to the future of the neutrino physics: super-neutrino beams or neutrino factory ?

  6. Measuring sin22q13 atreactors • Clean signal, no cross talk with d and matter effects • Relatively cheap compared to accelerator based experiments • Provides the direction to the future of neutrino physics • Rapidly deployment possible at reactors: Pee  1 sin22q13sin2 (1.27Dm213L/E)  cos4q13sin22q12sin2 (1.27Dm212L/E) at LBL accelerators: Pme ≈ sin2q23sin22q13sin2(1.27Dm223L/E) + cos2q23sin22q12sin2(1.27Dm212L/E)  A(r)cos2q13sinq13sin(d) Small-amplitude oscillation due to 13 Large-amplitude oscillation due to 12

  7. Recommendation of APS study report: 2004.11.4 APS

  8. neutrino detection: Inverse-β reaction in liquid scintillator t  180 or 28 ms(0.1% Gd) n + p  d + g (2.2 MeV) n + Gd  Gd* + g’s(8 MeV) Neutrino Event: coincidence intime, space and energy Neutrino energy: 1.8 MeV: Threshold 10-40 keV

  9. Reactor Experiment: comparing observed/expected neutrinos: • Palo Verde • CHOOZ • KamLAND Typical precision: 3-6%

  10. How to reach 1% precision ? • Increase statistics: • Use more powerful nuclear reactors • Utilize larger target mass, hence larger detectors • Reduce systematic uncertainties: • Reactor-related: • Optimize baseline for best sensitivity and smaller residual errors • Near and far detectors to minimize reactor-related errors • Detector-related: • Use “Identical” pairs of detectors to do relative measurement • Comprehensive program in calibration/monitoring of detectors • Interchange near and far detectors (optional) • Background-related • Go deeper to reduce cosmic-induced backgrounds • Enough active and passive shielding

  11. Daya Bay nuclear power plant • 4 reactor cores, 11.6 GW • 2 more cores in 2011, 5.8 GW • Mountains near by, easy to construct a lab with enough overburden to shield cosmic-ray backgrounds

  12. DYB NPP region - Location and surrounding Convenient Transportation,Living conditions, communications 55 km

  13. ~350 m ~98 m ~210 m ~97 m Cosmic-muons at the laboratory • Apply modified Gaisser parametrization for cosmic-ray flux at surface • Use MUSIC and mountain profile to estimate muon flux & energy

  14. Baseline optimization and site selection • Neutrino spectrum and their error • Neutrino statistical error • Reactor residual error • Estimated detector systematical error: total, bin-to-bin • Cosmic-rays induced background (rate and shape) taking into mountain shape: fast neutrons, 9Li, … • Backgrounds from rocks and PMT glass

  15. Best location for far detectors Rate only Rate + shape

  16. The Layout Far: 80 ton 1600m to LA, 1900m to DYB Overburden: 350m Muon rate: 0.04Hz/m2 • Total Tunnel length • ~2700 m • Detector swapping • in a horizontal tunnel cancels most detector systematic error. Residual error ~0.2% • Backgrounds • B/S of DYB,LA ~0.5% • B/S of Far ~0.2% • Fast Measurement • DYB+Mid, 2008-2009 • Sensitivity (1 year) ~0.03 • Full Measurement • DYB+LA+Far, from 2010 • Sensitivity (3 year) <0.01 LA: 40 ton Baseline: 500m Overburden: 112m Muon rate: 0.73Hz/m2 0% slope 0% slope Mid: Baseline: ~1000m Overburden: 208m 0% slope DYB: 40 ton Baseline: 360m Overburden: 98m Muon rate: 1.2Hz/m2 Access portal 8% slope

  17. Site investigation completed

  18. Tunnel construction • A feasibility study and two conceptual designs have been completed by professionals • The tunnel length is about 3000m • Cost is estimated to be about ~ 3K $/m • Construction time is ~ 15-24 months • A similar tunnel on site as a reference

  19. Baseline detector design: multiple neutrino modules and multiple vetos Redundancy is a key for the success of this experiment

  20. Neutrino detector: multiple modules Two modules at near sites Four modules at far site: Side-by-side cross checks • Multiple modules for side-by-side cross check • Reduce uncorrelated errors • Smaller modules for easy construction, moving, handing, … • Small modules for less sensitivity to scintillator aging, details of the light transport, …

  21. Central Detector modules • Three zones modular structure: I. target: Gd-loaded scintillator II. g-ray catcher: normal scintillator III. Buffer shielding: oil • Cylindrical module for easy construction • Reflection at top and bottom for cost saving • Module: 5 m high, 5 m diameter • ~ 200 8”PMT/module • Photocathode coverage: 5.6 %  10%(with reflector) • Performance: energy resolution5%@8MeV, position resolution ~ 14cm I III II Position resolution~14cm

  22. Detector dimension Oil buffer thickness g Catcher thickness

  23. Calibration and Monitoring • Source calibration: energy scale, resolutions, … • Deployment system • Automatic: quick but limited space points • Manual: slow but everywhere • Choices of sources: energy(0.5-8 MeV), activity(<1KHz), g/n,… • Cleanness • Calibration with physics events: • Neutron capture • Cosmic-rays • LED calibration: PMT gain, liquid transparency, … • Environmental monitoring: temp., voltage, radon, … • Mass calibration and high precision flow meters • Material certification

  24. The muon detector and the shielding • Water shield also serves as a • Cherenkov counter for tagging muons • Water Cherenkov modules • along the walls and floor • Augmented with a muon • tracker: RPCs • Combined efficiency of Cherenkov and tracker > 99.5% with error measured to better than 0.25%

  25. Alternative Design: Aquarium Tunnel • Dry detectors • Easier to deploy detectors • Can access detectors • Radon from rock can easily diffuse into detectors during data taking • Less temperature regulation

  26. Water Buffer & VETO • At least 2m water buffer to shield backgrounds from neutrons and g’s from lab walls • Cosmic-muon VETO Requirement: • Inefficiency < 0.5% • known to <0.25% • Solution: Two active vetos • Active water buffer, Eff.>95% • Muon tracker, Eff. > 90% • RPC • Water tanks • scintillator strips • total ineff. = 10%*5% = 0.5% • Two vetos to cross check each other and control uncertainty Neutron background vs water shielding thickness 2.5 m water

  27. Background related error • Need enough shielding and active vetos • How much is enough ?  error < 0.2% • Uncorrelated backgrounds: U/Th/K/Rn/neutron Single gamma rate @ 0.9MeV < 50Hz Single neutron rate < 1000/day 2m water + 50 cm oil shielding • Correlated backgrounds: n  Em0.75 Neutrons:>100 MWE + 2m water Y.F. Wang et al., PRD64(2001)0013012 8He/9Li: > 250 MWE(near), >1000 MWE(far) T. Hagner et al., Astroparticle. Phys. 14(2000) 33

  28. Systematic error comparison

  29. 2 2 3 4 Setting Up The Experiment • Bring up a pair of detectors at a time • Begin to observe  • One month: N  17,500/module • Begin to measure background, cross • calibrate detectors at Daya Bay near • site Start in Jun 2009 Tunnel entrance 1 • Move detectors 1 and 3 to Mid Hall • Keep detectors 2 & 4 at Daya Bay near • site • Begin data taking with the Near-Mid • configuration (2) When Mid Hall is ready in Sept 2009 1 Tunnel entrance

  30. 1 1 2 4 3 6 4 8 7 5 5 6 2 3 Setting Up The Experiment (cont) • Move detector 5 to Far Hall, and • detector 6 to Ling Ao Near Hall • Begin to take data with the default • Near-Far configuration (3) When Ling Ao & Far Halls are ready in Jun 2010 Tunnel entrance • Move detector 7 to Far Hall • and detector 8 to Ling Ao Near Hall • to complete the configuration (4) Deployment is completed Tunnel entrance

  31. Sensitivity to Sin22q13 • Reactor-related correlated error: sc ~ 2% • Reactor-related uncorrelated error: sr ~ 1-2% • Calculated neutrino spectrum shape error: sshape ~ 2% • Detector-related correlated error: sD ~ 1-2% • Detector-related uncorrelated error: sd ~ 0.5% • Background-related error: • fast neutrons: sf ~ 100%, • accidentals: sn ~ 100%, • isotopes(8Li, 9He, …) : ss ~ 50-60% • Bin-to-bin error: sb2b ~ 0.5% Many are cancelled by the near-far scheme and detector swapping

  32. Sensitivity to Sin22q13 Other physics capabilities: Supernova watch, Sterile neutrinos, …

  33. Daya Bay collaboration Europe (3) JINR, Dubna, Russia Kurchatov Institute, Russia Charles University, Czech Republic North America (13) LBNL, BNL, Caltech, UCLA Univ. of Houston, Iowa state Univ. Univ. of Wisconsin, Illinois Inst. Tech. , Princeton, RPI, IIT, Virginia Tech., Univ. of Illinois Asia (13) IHEP, CIAE,Tsinghua Univ. Zhongshan Univ.,Nankai Univ. Beijing Normal Univ., Nanjing Univ. Shenzhen Univ., Hong Kong Univ. Chinese Hong Kong Univ. Taiwan Univ., Chiao Tung Univ., National United Univ. ~ 110 physicists

  34. Organization of Daya Bay Collaboration • Governed by Bylaws. • Institutional board: with one representative from each member institution and two spokespersons. • Executive board (two-year term): Y.F. Wang (China) A. Olshevski (Russia) C.G. Yang (China) K.B. Luk (U.S.) M.C. Chu (Hong Kong) R. McKeown (U.S.) Y. Hsiung (Taiwan) • Scientific spokespersons (two-year term): Y.F. Wang (China), K.B. Luk

  35. Project management • Project managers: Y.F. Wang, W.Edwards • Chief engineers: H.L. Zhuang, R. Brown • Sub-system managers: • Anti-neutrino detector: J.W. Zhang, K. Heeger • Muon detector: L. Littenberg, C.G. Yang • Calibration: R. McKeown • Trigger/DAQ/electronics: X.N. Li, C. White • Offline/computing: J. Cao, C. Tull • Civil construction: H.Y. Zhang

  36. Funding • Daya Bay is the first US-China • collaboration with equal partnership • in nuclear and particle physics • China plans to provide civil construction • and ~half of the detector systems; U.S. • plans to bear ~half of the detector cost • Committed funding from the Chinese • Academy of Sciences, the Ministry of Science and Technology, and • Natural Science Foundation of China, China Guangdong Nuclear Power • Group, Shenzhen municipal and Guangdong provincial government • Gained strong support from: • China Guangdong Nuclear Power Group • China atomic energy agency • China nuclear safety agency • Supported by BNL/LBNL seed funds and $800K R&D fund from DOE

  37. Schedule • begin civil construction April 2007 • Bring up the first pair of detectors Jun 2009 • Begin data taking with the Near-Mid • configuration Sept 2009 • Begin data taking with the Near-Far • configuration Jun 2010

  38. Summary • The Daya Bay experiment will reach a sensitivity of ≤ 0.01 for sin2213 • The Daya Bay Collaboration continues to grow • Bylaws approved; • Working groups established; • Management structure introduced • Design of detectors is in progress and R&D is ongoing • Engineering designof tunnels and infrastructures will begin soon • Continue to receive strong support from Chinese agencies • Plan to start deploying detectors in 2009, and begin full operation in 2010

  39. No good reason(symmetry) for sin22q13 =0 • Even if sin22q13 =0 at tree level, sin22q13 will not vanish at low energies with radiative corrections • Theoretical models predict sin22q13 ~ 0.001-0.1 An experiment with a precision for sin22q13 Better than 1% is desired An improvement of an order of magnitude over previous experiments

  40. How Neutrinos are produced in reactors ? The most likely fission products have a total of 98 protons and 136 neutrons, hence on average there are 6 n which will decay to 6p, producing 6 neutrinos Neutrino flux of a commercial reactor with 3 GWthermal : 6 1020 /s

  41. Prediction of reactor neutrino spectrum • Reactor neutrino rate and spectrum depends on: • The fission isotopes and their fission rate, uncorrelated ~ 1-2% • Fission rate depends on thermal power, uncorrelated ~ 1% • Energy spectrum of weak decays of fission isotopes, correlated ~ 1% • Three ways to obtain reactor neutrino spectrum: • Direct measurement at near site • First principle calculation • Sum up neutrino spectra from 235U, 239Pu, 241Pu and 238U 235U, 239Pu, 241Pu from their measured b spectra 238U(10%) from calculation (10%) • They all agree well within 3%

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