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Determining the Neutrino Mixing Angle  13 at Daya Bay

This article discusses the determination of the neutrino mixing angle θ13 at the Daya Bay Experiment, its importance, and the collaboration between Daya Bay and BNL. It also explores the connection between quarks and neutrinos and the impact of precise neutrino measurements on our understanding of the cosmos.

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Determining the Neutrino Mixing Angle  13 at Daya Bay

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  1. Determining the Neutrino Mixing Angle 13at Daya Bay • Motivation • Reactor anti-ne • Collaboration/BNL involvement • Daya Bay Experiment Steve Kettell BNL

  2. Neutrinos • Connecting Quarks to the Cosmos: One of the eleven `profound questions’ addresses the mass and mixing of neutrinos. (2003) • Quantum Universe: “Detailed studies of the properties of neutrinos  their masses, how they mix, and whether they are Majorana particles will tell us whether neutrinos conform to the patterns of ordinary matter or whether they are leading us to the discovery of new phenomena.” (2004) Steve Kettell, BNL HENP PAC Meeting

  3. Recommendations of APS  Study Group (11/04) on fast track Steve Kettell, BNL HENP PAC Meeting

  4. Recommendations from NuSAG (3/06) A reactor experiment is valuable regardless of its timing with respect to an accelerator experiment. Steve Kettell, BNL HENP PAC Meeting

  5. Recommendations from NuSAG (2) Steve Kettell, BNL HENP PAC Meeting

  6. Neutrino Mixing • For three generations of massive neutrino, the weak eigenstates are • not the same as the mass eigenstates: Pontecorvo-Maki- Nakagawa-Sakata Matrix • PMNS matrix parameterization: Majorana phases solarnreactornatmosphericnneutrinoless reactornaccelerator LBL n accelerator LBL n double- decay Six parameters: 2 m2, 3 angles, 1 phase+ 2 Majorana phases Steve Kettell, BNL HENP PAC Meeting

  7. Neutrino Oscillation • The probability ofne X disappearance is: + • The probability ofnm neappearance is given by: Complementary m232 =(2.4+0.4-0.3)10-3 eV2 23  45 m221 =(7.8+0.6-0.5)10-5 eV2 12 =(32+4-3) Dm231Dm232 >> Dm221 q12andq23are large Unknowns: sin2213, , sign of m232 Steve Kettell, BNL HENP PAC Meeting

  8. Current Knowledge of 13 At m231 = 2.4  103 eV2, sin22 < 0.15 Established technique  with improvements q13 q12 Dm12 Limit on q13 from Chooz 2.7%, 6% without near detectors • limited statistics • reactor-related systematic errors: • - energy spectrum of e (~2%) • - time variation of fuel composition (~1%) • detector-related systematic error (1-2%) • background-related error (1-2%) allowed region Steve Kettell, BNL HENP PAC Meeting

  9. Detection of antineutrinos in liquid scintillator e  p  e+ + n(prompt)  + p  D + (2.2 MeV) (delayed) • + Gd  Gd*  Gd + ’s(8 MeV) (delayed) n m From Bemporad, Gratta and Vogel Arbitrary Observable n Spectrum Cross Section Flux • The reaction is the inverse -decay in Gd-doped liquid scintillator: 0.3b 50,000b • Time- and energy-tagged signal is a good • tool to suppress background events. • Energy of eis given by: E Te+ + Tn + (mn - mp) + m e+  Te+ + 1.8 MeV 10-40 keV Steve Kettell, BNL HENP PAC Meeting

  10. How To Reach A Precision of 0.01 ? • Powerful nuclear power plant (11.617.4 GWth) • Large detectors to reduce statistical error (420 tons) • 100-150k events/year at the far detector (2-3 years for 0.2%) • Near and far detectors to minimize reactor-related errors (2+1) • Optimize baseline to maximize sensitivity and further reduce any residual reactor-related errors • Identical detectors to reduce detector-related systematic error • Interchange near and far detectors to further reduce the detector systematic uncertainty • Sufficient overburden and shielding to reduce background • Comprehensive calibration to reduce detector systematic error Steve Kettell, BNL HENP PAC Meeting

  11. Location of Daya Bay 45 km 55 km Steve Kettell, BNL HENP PAC Meeting

  12. Far site 1600 m from Lingao 1900 m from Daya Overburden: 350 m Ling Ao Near 500 m from Lingao Overburden: 98 m Mid site ~1000 m from Daya Overburden: 208 m Ling Ao-ll NPP (under const.) 672 m (12% slope) Ling Ao NPP 8% slope Daya Bay Near 360 m from Daya Bay Overburden: 97 m Entrance portal Daya Bay NPP Total length: ~3200 m Steve Kettell, BNL HENP PAC Meeting

  13. The Site LingAo II NPP: 2  2.9 GWth Ready by 2010 Daya Bay NPP: 2  2.9 GWth LingAo NPP: 2  2.9 GWth Steve Kettell, BNL HENP PAC Meeting

  14. The Daya Bay Collaboration X. Guo, N. Wang, R. Wang Beijing Normal University, Beijing 100875, China L. Hou, B. Xing, Z. Zhou China Institute of Atomic Energy, Beijing 102413, China M.C. Chu, W.K. Ngai Chinese University of Hong Kong, Hong Kong, China J. Cao, H. Chen, J. Fu, J. Li, X. Li, Y. Lu, Y. Ma, X. Meng, R. Wang, Y. Wang, Z. Wang, Z. Xing, C. Yang, Z. Yao, J. Zhang, Z. Zhang, H. Zhuang, M. Guan, J. Liu, H. Lu, Y. Sun, Z. Wang, L. Wen, L. Zhan, W. Zhong Institute of High Energy Physics, Beijing 100039, China X. Li, Y. Xu, S. Jiang Nankai University, Tianjin 300071, China y. Chen, H. Niu, L. Niu Shenzhen University, Shenzhen 518060, China S. Chen, Q. Su Tsinghua University, Beijing 100084, China K.S. Cheng, J.K.C. Leung, C.S.J. Pun, T. Kwok, H.H.C. Wong, R.H.M. Tsang University of Hong Kong, Hong Kong, China H. Liang, G. Jin, J. Wang, Q. Wang, X. Yu, Y. Zhou University of Science and Technology of China, Hefei 230026, China Z. Li, C. Zhou Zhongshan University, Guangzhou 510275, China B.Y. Hsiung National Taiwan University, Taipei, Taiwan, Republic of China Steve Kettell, BNL HENP PAC Meeting

  15. The Daya Bay Collaboration (cont.) Yu. Gornushkin, I. Nemchenok, A. Olchevski, E. Yakushev Joint Institute of Nuclear Research, Dubna, Russia V.I. Aleshin, Yu.V. Gaponov, V.I. Kopeikin, V.P. Martemyanov, L.A. Mikaelyan, V.G. Tarasenkov, V.N. Vyrodov Kurchatov Institute, Moscow, Russia M. Bishai, M. Diwan, D. Jaffe, J. Frank, A. Garnov, R. Hahn, S. Kettell, L. Littenberg, K. Li, B. Viren, M. Yeh Brookhaven National Laboratory, Upton, NY 11973-5000, USA R.D. McKeown, C. Mauger, C. Jillings California Institute of Technology, Pasadena, CA 91125, USA B.L. Young, K. Whisnant Iowa State University, Ames, Iowa 50011, USA W. Edwards, K. Heeger, K.B. Luk University of California and Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA V. Ghazikhanian, H.Z. Huang, S. Trentalange, C. Whitten Jr. University of California, Los Angeles, CA 90095, USA K. Lau, B.W. Mayes, L. Pinsky University of Houston, Houston, Texas 77204, USA J.C. Peng University of Illinois, Urbana-Champaign, Illinois 61801, USA Steve Kettell, BNL HENP PAC Meeting

  16. Why BNL? • The Physics is compelling! and a critical step to CP • BNL provides a strong National Laboratory presence that will make this experiment viable for the DOE. • BNL has a rich and storied tradition in n physics: in both the Physics and Chemistry departments • BNL Chemistry has been involved in liquid scintillator research for Daya Bay for 3 years • This experiment provides a bridge from the current Physics Department effort on MINOS to a long-baseline effort to measure CP violation in the neutrino sector. Steve Kettell, BNL HENP PAC Meeting

  17. BNL involvement in Daya Bay • Formally joined collaboration at Feb. 2006 meeting in Beijing • Member of Institutional Board (Kettell) • Lead of liquid scintillator task force (Hahn,Yeh) • Lead of muon veto task force (Littenberg, Diwan, Bishai) • Central detector task force (Kettell) • Simulations task force (Jaffe) • Project and other engineering resources available Steve Kettell, BNL HENP PAC Meeting

  18. Gd-loaded Liquid Scintillator Chooz Significantly reduces backgrounds due to the short neutron capture time and high capture energy Palo Verde • R&D effort at BNL: • - Gd (carboxylate ligands) in PC and dodecane • - all stable for a year • - att. Length > 15m • - promising new scintillator: Linear Alkyl Benzene (LAB) • BNL has successfully loaded 1% Gd into 100% LAB • Gd-LAB has much better transparency at < 400 nm and at least ~50% improved optical transparency at 430 nm, compared to Gd-PC Steve Kettell, BNL HENP PAC Meeting

  19. 20t Gd-doped LS buffer gamma catcher Conceptual Design of Detector Modules • Three-layer structure: I. Target: Gd-loaded liquid scintillator II. Gamma catcher: liquid scintillator, 45cm III. Buffer shielding: mineral oil, ~45cm • Possibly with diffuse reflection at ends. For ~200 PMT’s around the barrel: Steve Kettell, BNL HENP PAC Meeting

  20. Cross Section of Tunnel For Daya Bay Experiment 7.2 m 1.2 m 1.2 m 3.2 m 3.2 m 0.8 m Steve Kettell, BNL HENP PAC Meeting

  21. ~350 m ~98 m ~208 m ~97 m Cosmic-ray Muon • Apply a modified Gaisser parameterization for cosmic-ray flux at surface • Use MUSIC and mountain profile to estimate muon flux & energy near site far site Steve Kettell, BNL HENP PAC Meeting

  22. Conceptual Design of Shield-Muon Veto PMT's detector module Tracker rock 2m of water ~0.05 Neutron background vs. thickness of water • Detector modules enclosed by 2m of water to shield neutrons (and gamma-rays) • Water shield also serves as a Cherenkov veto • Augmented with a muon tracker: scintillator or RPC's • Combined efficiency of Cherenkov and tracker > 99.5% Steve Kettell, BNL HENP PAC Meeting

  23. Background • Natural Radioactivity: PMT glass, Rock, Radon in the air, etc • Slow neutron, and fast neutron • - Neutrons produced in rock and water shield (99.5% veto efficiency) • Cosmogenic isotopes: 8He/9Li which can -n decay - Cross section measured at CERN (Hagner et. al.) - Can be measured in-situ, even for near detector with muon rate ~ 10 Hz. • Use a modified Palo Verde Geant3 MC to model response of detector 20t module The above numbers are before shower-muon cut. For reference, 560(80) neutrino events per detector per day at the near(far) site Daya Bay Experiment

  24. Systematic Uncertainty • * • No Vertex cut. • Residual detection error is dominated by the neutron energy cut at 6 MeV • arises mainly from the energy-scale uncertainties. (It is ~0.2% for a 1% • energy-scale error at 6 MeV.) • Positron energy cut is negligible. Statistical Error (3 years): 0.2% Residual systematic error: ~ 0.2% Daya Bay Experiment

  25. Sensitivity of sin2213 • Daya Bay site - baseline = 360 m - target mass = 40 ton - B/S = ~0.5% • LingAo site - baseline = 500 m - target mass = 40 ton - B/S = ~0.5% • Far site - baseline = 1900 m to DYB cores 1600 m to LA cores - target mass = 80 ton - B/S = ~0.2% • Three-year run (0.2% statistical error) • Detector residual error = 0.2% • Use rate and spectral shape 90% confidence level 2 near + far near (40t) + mid (40 t) 1 year Steve Kettell, BNL HENP PAC Meeting

  26. Summary and Prospects • The Daya Bay nuclear power facility in China and the mountainous topology in the vicinity offer an excellent opportunity for carrying out a measurement of sin2213 at a sensitivity of 0.01. • The Chinese funding agencies have agreed to a request of RMB 150 million to complete civil construction and ~half of the detector. • NuSAG has endorsed US participation in a 13 experiment, HEPAP is evaluating 13 experiments as part of the Roadmap, and we await a decision by DOE. • BNL/LBNL submitted R&D request to DOE for FY06 in January 2006. • Will complete a conceptual design of detectors, tunnels and underground facilities in 2006, aiming for CD1 this year and CD2 in 2007. • Plan to commission the Fast Deployment scheme in early FY2010, and Full Operation late in FY2010. Steve Kettell, BNL HENP PAC Meeting

  27. Backup Steve Kettell, BNL HENP PAC Meeting

  28. Tunnel construction • The total tunnel length is ~3 km • Preliminary engineering design: Cost ~$3K/m • Construction time ~15-24 months • A similar tunnel exists on site as a reference 7.2 m 7.2 m Steve Kettell, BNL HENP PAC Meeting

  29. Bore Drilling Ongoing and will finish by the end of March. bursa Steve Kettell, BNL HENP PAC Meeting

  30. Steve Kettell, BNL HENP PAC Meeting

  31. Prototype Detector at IHEP • Constructing a 2-layer prototype with • 0.5 t Gd-doped LS enclosed in 5 t of • mineral oil, and 45 8” PMT's to evaluate • design issues at IHEP, Beijing PMT mount Steel tank Front-end board (version 2) acrylic vessel Steve Kettell, BNL HENP PAC Meeting

  32. The Aberdeen Tunnel Experiment • Study cosmic muons & cosmogenic background in Aberdeen Tunnel, Hong Kong. Overburden ~ Daya Bay sites similar geology between Aberdeen and Daya Bay Installing proptubes in Sept, 2005 Steve Kettell, BNL HENP PAC Meeting

  33. Management Structure • The Collaboration approved bylaws (2/06). • Institutional Board, consisting of one representative from each Member Institution and two spokespersons, established (2/06). • Executive Board established (2/06): Y. Wang (China) A. Olshevski (Russia) C. Yang (China) K.B. Luk (US) M.C. Chu (Hong Kong) R. McKeown (US) Y. Hsiung (Taiwan) • Scientific spokespersons are chosen: Y. Wang (China), K.B. Luk (US) • Task forces on communication, antineutrino detector, muon veto, liquid scintillator, simulation, and calibration set up. Each task is led by at least one member from China and one from US. • Begin to discuss the Construction Project management. Steve Kettell, BNL HENP PAC Meeting

  34. What Target Mass? m231 = 2  10-3 eV2 DYB: B/S = 0.5% LA: B/S = 0.4% Mid: B/S = 0.1% Far: B/S = 0.1% Solid lines : near+far Dashed lines : mid+far Systematic error (per site): Black : 0.6% Red : 0.25% Blue : 0.12% Steve Kettell, BNL HENP PAC Meeting

  35. Where To Place The Detectors ? Sin2(2q13) = 0.1 Dm231 = 2.5 x 10-3 eV2 Sin2(2q12) = 0.825 Dm221 = 8.2 x 10-5 eV2 ne far detector to measure changes at L2 reactor near detector to measure raw flux at L1 Steve Kettell, BNL HENP PAC Meeting

  36. Where To Place The Detectors At Daya Bay? ~1700 m Ling Ao Daya Bay Steve Kettell, BNL HENP PAC Meeting

  37. A Versatile Site • Rapid deployment: • Daya near site + mid site • 0.7% reactor systematic • error • Full operation: • (1) Two near sites + Far site • (2) Mid site + Far site • (3) Two near sites + Mid site + Far site • Internal checks, each with different • systematic Steve Kettell, BNL HENP PAC Meeting

  38. What Have We Learned From Chooz? P = 8.4 GWth L = 1.05 km D = 300 mwe 5 t Gd-loaded liquid scintillator to detect Rate: ~5 events/day/t (full power) including 0.2-0.4 bkg/day/t ~3000 ecandidates (included 10% bkg) in 335 days e + p  e+ + n e+ + e-  2 x 0.511 MeV  n + Gd  8 MeV of s;  ~ 30 s Steve Kettell, BNL HENP PAC Meeting

  39. Reactor anti-e For 235U, for instance, an average of 6 esare producedper fission (~200 MeV). -42 e/MeV/fission 3 GWthgenerates 61020 ne per sec Steve Kettell, BNL HENP PAC Meeting

  40. Time Variation of Fuel Composition 235U 239Pu 238U 241Pu 0 0.5 1 1.5 2 2.5 3 3.5 normalized flux times cross section (arbitrary units) 2 3 4 5 6 7 8 9 10 E (MeV) Typically known to ~1% Steve Kettell, BNL HENP PAC Meeting

  41. How To Measure 13 With Reactor e? Steve Kettell, BNL HENP PAC Meeting

  42. Background 12B 12N Keep everything as radioactively pure as possible! KamLAND Depends on the flux of cosmic muons in the vicinity of the detector Go as deep as possible! Steve Kettell, BNL HENP PAC Meeting

  43. -n Decay Of 8He And 9Li τ½ = 178 ms 49.5% Correlated τ½ = 119 ms 16% Correlated Correlated final state: β+n+2α Correlated final state: β+n+7Li Steve Kettell, BNL HENP PAC Meeting

  44. Background 20t module • Use a modified Palo-Verde-Geant3-based MC to model response of detector. • Cosmogenic isotopes: 8He/9Li which can -n decay - Cross section measured at CERN (Hagner et. al.) - Can be measured in-situ, even for near detector with muon rate ~ 10 Hz. The above number is before shower-muon cut which can further reduce cosmogenic background. Steve Kettell, BNL HENP PAC Meeting

  45. Background estimated by GEANT MC simulation Steve Kettell, BNL HENP PAC Meeting

  46. Calibration • Radioactive Source 137Cs, 22Na, 60Co, 54Mn, 65Zn , 68Ge, Am-Be 252Cf, Am-Be • Gamma generator p+19F→ α+16O*+6.13MeV; p+11B→ α+8Be*+11.67MeV • Backgrounds 40K, 208Tl, cosmic-induced neutrons, Michel’s electrons, … • LED calibration KI & CIAE Hong Kong Steve Kettell, BNL HENP PAC Meeting

  47. Synergy of Reactor and Accelerator Experiments 90% CL Reactor w 100t (3 yrs) + Nova Nova only (3yr + 3yr) Reactor w 10t (3yrs) + Nova Reactor experiments can help in Resolving the23 degeneracy (Example: sin2223 = 0.95 ± 0.01) Δm2 = 2.5×10-3 eV2sin2213 = 0.05 Reactor w 100t (3 yrs) +T2K T2K (5yr,n-only) Reactor w 10t (3 yrs) +T2K 90% CL 90% CL Reactor experiments provide a better determination of 13 McConnel & Shaevitz, hep-ex/0409028 Steve Kettell, BNL HENP PAC Meeting

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