1. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 1 ν

2. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 2 ν 大亚湾 核反应堆 中微子实验 The Daya Bay Reactor Neutrino Experiment and ϑ 13 Manfred Jeitler HEPHY 19 October 2012

3. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 3 Material from Observation of Electron Anti-neutrino Disappearance at Daya Bay Yifang Wang Institute of High Energy Physics CERN ， March 20, 2012 https://indico.cern.ch/conferenceDisplay.py?confId=181843 and from a private trip to China in July 2012 see also Invited Talk by Yifang Wang at VCI 2013 !

4. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 4 Neutrinos & Neutrino Oscillation n Fundamental building blocks of matter: n Neutrino mass: the central issue of neutrino physics –Tiny mass but huge amount –Influence on Cosmology: evolution, large scale structure, … –Only evidence beyond the Standard Model n Neutrino oscillation: a great method to probe the mass e e   Oscillation probability ： P  e    sin   sin 2 (1.27  m 2 L/E) Oscillation amplitude Oscillation frequency

5. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 5 Neutrino Oscillation P  e    sin   sin 2 (1.27  m 2 L/E) Mixing angle (Amplitude) “baseline” m 1 2 – m 2 2 not (m 1 – m 2 ) 2 ! numerical factor for using convenient units (km, GeV) neutrino energy

6. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 6 CKM Matrix and PMNS Matrix 1 0 0 0 1 0 0 0 1 CKM: (quarks) 1 1 0 0 1 1 0 0 1 PMNS: (neutrinos) 1.0 0.2 0.0 0.2 1.0 0.0 0.0 0.0 1.0  0.8 0.5 -0.2 -0.3 0.7 0.6 0.4 -0.4 0.8 

7. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 7 CKM Matrix and PMNS Matrix n Cabibbo-Kobayashi-Maskawa n Pontecorvo-Maki-Nakagawa-Sakata

8. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 8... and what about the masses? normal hierarchy inverted hierarchy or maybe:

9. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 9 Daya Bay: for a New Type of Oscillation Goal ： search for a new oscillation  13 n Neutrino mixing matrix: 1 2 3  12 solar neutrino oscillation  23 atmospheric neutrino oscillation  13 ? Unknown mixing parameters:  13,  + 2 Majorana phases Need sizable  13 for the  measurement

10. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 10 How to measure which type of oscillation? solar atmospheric reactor

11. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 11 Two ways to measure  13 Reactor experiments: P ee  1  sin 2 2   sin 2 (1.27  m 2  L/E)  cos 4   sin 2 2   sin 2 (1.27  m 2  L/E) Long baseline accelerator experiments: P  e ≈ sin 2   sin 2 2   sin 2 (1.27  m 2  L/E) + cos 2   sin 2 2   sin 2 (1.27  m 2 12 L/E)  A(  )  cos 2  13 sin    sin(  ) Small-amplitude oscillation due to  13 Large-amplitude oscillation due to  12 At reactors:  Clean signal, no cross talk with  and matter effects  Relatively cheap compared to accelerator based experiments  Provides the direction to the future of neutrino physics

12. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 12 How to make neutrinos? n Accelerator: –Muon neutrinos (from pion decay: π  μ ν μ ) –expensive –Example: CNGS (Cern to Gran Sasso) n Reactor: n Fusion reactor –Sun –Electron neutrinos (p + p  d + e + + ν e ) n Fission reactor –Nuclear power plants (such as Daya Bay) –Electron anti-neutrinos (n  p + e - + ν e )

13. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 13...o 13 How to see neutrinos?... without being blinded by the background?

14. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 14 How to see neutrions? (from a fission reactor): original method of discoverers (Clyde L. Cowan and Frederick Reines, 1956):

15. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 15 How to see neutrions? 向前 一小步 文明 一大步 Xiàng qián yī xiǎo bù wénmíng yī dà bù Forward one small step, for civilization, a big step

16. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 16 Daya Bay Experiment: Layout n Relative measurement to cancel Correlated Systematic Errors –2 near sites, 1 far site n Multiple Antineutrino Detector modules at each site to reduce Uncorrelated Syst. Errors –Far: 4 modules ， near: 2 modules n Multiple muon detectors to reduce veto efficiency uncertainties –Water Cherenkov ： 2 layers –RPC ： 4 layers at the top + telescopes Redundancy !!! Cross check; Reduce errors by 1/  N

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18. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 18 Underground Labs Overburden （ MWE ） R  （ Hz/m 2 ） E  （ GeV ） D1,2 (m) L1,2 (m) L3,4 (m) EH12501.27573648571307 EH22650.95581348480528 EH38600.056137191215401548

19. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 19 Anti-neutrino Detector (AD) Target: 20 t, 1.6m  -catcher: 20t, 45cm Buffer: 40t, 45cm Total weight: ~110 t  Three zones modular structure: I. target: Gd-loaded scintillator  -catcher: normal scintillator III. buffer shielding: oil  192 8” PMTs/module  Two optical reflectors at the top and the bottom, Photocathode coverage increased from 5.6% to 12% ~ 163 PE/MeV

20. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 20 10-40 keV Neutrino energy: Neutrino Event: coincidence in time, space and energy Neutrino Detection: Gd-loaded Liquid Scintillator 1.8 MeV: Threshold  s(0.1% Gd) n + p  d +  (2.2 MeV) n + Gd  Gd* +  (8 MeV)

21. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 21 Muon Veto Detector n RPCs –4 layers/module –54 modules/near hall, 81 modules/far hall – 2 telescope modules/hall n Water Cerenkov detector –Two layers, separated by Tyvek/PE/Tyvek film –288 8” PMTs for near halls; 384 8” PMTs for the far hall n Water processing –High purity de-ionized water in pools also for shielding –First stage water production in hall 4 –Local water re-circulation & purification Two active cosmic-muon veto’s  Water Cerenkov: Eff.>97%  RPC Muon tracker: Eff. > 88%

22. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 22 Two Antineutrino Detectors Installed in Hall 1

23. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 23 Hall 1 (two Antineutrino Detectors) Started Operation on Aug. 15, 2011

24. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 24 One AD installed in Hall 2 Physics Data Taking Started on Nov.5, 2011

25. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 25 Three Antineutrino Detectors installed in Hall 3 Physics Data Taking Started on Dec. 24, 2011

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27. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 27 Compare: High-tech, high-precision High-Energy Physics lab (Protvino, Russia)

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32. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 32 中国科学院 大亚湾中微子实验站

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54. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 54 Event Signature and Backgrounds n Signature: –Prompt: e +, 1-10 MeV, –Delayed: n, 2.2 MeV@H, 8 MeV @ Gd –Capture time: 28  s in 0.1% Gd-LS n Backgrounds –Uncorrelated: random coincidence of  n or nn  from U/Th/K/Rn/Co… in Liquid Scintillator, Stainless Steel Vessel, PMT, Rock, … »n from  -n,  -capture,  -spallation in Liquid Scintillator, water & rock –Correlated: »Fast neutrons: prompt  n scattering, delayed  n capture » 8 He/ 9 Li: prompt  decay, delayed  n capture »Am-C source: prompt  rays, delayed  n capture  -n: 13 C(α,n) 16 O

55. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 55 Neutrino Event Selection n Pre-selection –Reject Flashers –Reject Triggers within (-2 μs, 200 μs) to a tagged water pool muon n Neutrino event selection –Multiplicity cut »Prompt-delayed pairs within a time interval of 200 μs »No triggers (E > 0.7MeV) before the prompt signal and after the delayed signal by 200 μs –Muon veto »1s after an Antineutrino-Detector shower muon »1ms after an Antineutrino-Detector muon »0.6ms after an Water Pool muon –0.7MeV < E prompt < 12.0MeV –6.0MeV < E delayed < 12.0MeV –1μs < Δt e + -n < 200μs

56. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 56 Backgrounds – 8 He/ 9 Li Cosmic  produced 9 Li/ 8 He in LS –  -decay + neutron emitter –  8 He/ 9 Li ) = 171.7ms/257.2ms – 8 He/ 9 Li, Br(n) = 12%/48%, 9 Li dominant –Production rate follow E  0.74 power law n Measurement: –Time-since-last-muon fit –Improve the precision by reducing the muon rate: »Select only muons with an energy deposit >1.8MeV within a [10us, 200us] window »Issue: possible inefficiency of 9 Li –Results w/ and w/o the reduction is studied 9 Li yield Error follows

57. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 57 Baseline n Survey: –Methods: GPS, Total Station, laser tracker, level instruments, … –Results are compared with design values, and Power Plant coordinates –Data processed by three independent software n Results: sum of all the differences less than 28 mm n Uncertainty of the fission center from reactor simulation: –2 cm horizontally –20 cm vertically n The combined baseline error is 35 mm, corresponding to a negligible reactor flux uncertainty (<0.02%) By Total station By GPS

58. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 58 Reactor Neutrinos n Reactor neutrino spectrum n Thermal power, W th, measured by KIT system, calibrated by KME method n Fission fraction, f i, determined by reactor core simulation Neutrino spectrum of fission isotopes S i (E ) from measurements n Energy released per fission e i Relative measurement  independent from the neutrino spectrum prediction Kopeikin et al, Physics of Atomic Nuclei, Vol. 67, No. 10, 1892 (2004)

59. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 59 Daily Rate n Three halls taking data synchronously allows near-far cancellation of reactor related uncertainties n Rate changes reflect the reactor on/off Predictions are absolute, multiplied by a normalization factor from the fitting

60. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 60 Predictions n Baseline n Target mass n Reactor neutrino flux n These three predictions are blinded before we fix our analysis cuts and procedures n They are opened on Feb. 29, 2012 n The physics paper is submitted to PRL on March 7, 2012

61. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 61 Complete Efficiency and Systematics TDR ： (0.18 - 0.38) %

62. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 62 Electron Anti-neutrino Disappearence Using near to predict far: Determination of α, β: 1)Set R=1 if no oscillation 2)Minimize the residual reactor uncertainty Observed ： 9901 neutrinos at far site, Prediction ： 10530 neutrinos if no oscillation R = 0.940 ±0.011 (stat) ±0.004 (syst) Spectral distortion consistent with oscillation

63. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 63 Summary n Electron anti-neutrino disappearance is observed at Daya Bay, together with a spectral distortion n A new type of neutrino oscillation is thus discovered R = 0.940 ±0.011 (stat) ±0.004 (syst), Sin 2 2  13 =0.092  0.016 (stat)  0.005(syst)  2 /NDF = 4.26/4 5.2 σ for non-zero θ 13

64. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 64 Competing experiment: RENO in South Korea http://indico.cern.ch/conferenceDisplay.py?confId=187213 Competing experiment: RENO in South Korea http://indico.cern.ch/conferenceDisplay.py?confId=187213  RENO was the first experiment to take data with both near and far detectors, from August 1, 2011.  RENO observed a clear disappearance of reactor antineutrinos.  RENO measured the last, smallest mixing angle  13 unambiguously that was the most elusive puzzle of neutrino oscillations  Surprisingly large !!! → A plenty of tasks ahead for neutrino physicists

65. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 65

66. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 66 B HEPHY’s personal connections to neutrios Baikal neutrino experiment Japan / KEK Daya Bay Wisconsin (leading IceCube Institute)

67. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 67 谢谢 !

68. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 68 If you want even more details....

69. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 69 ν 大亚湾 核反应堆 中微子实验 The Daya Bay Reactor Neutrino Experiment and ϑ 13 Manfred Jeitler HEPHY Nikolsdorfergasse 18 19 October 2012 16:30

70. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 70 Original papers F.P. An et al., Daya Bay Coll., “ A side-by-side comparison of Daya Bay anti- neutrino detectors”, arXiv: 1202.6181[physics.ins-det], submitted to NIM F.P. An et al., Daya Bay Coll., “Observation of electron anti-neutrino disappearance at Daya Bay”, arXiv: 1203.1669[hep-ex], submitted to PRL

71. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 71 mass hierarchy

72. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 72 Direct Searches in the Past n Palo Verde & Chooz: no signal T2K: 2.5  over bkg Minos: 1.7  over bkg Double Chooz: 1.7  Allowed region Sin 2 2  13 < 0.15 @ 90%C.L.  if  M 2 23 = 0.0024 eV 2 0 < Sin 2 2  13 < 0.12 @ 90%C.L. NH 0 < Sin 2 2  13 < 0.19 @ 90%C.L. IH sin 2 2θ 13 = 0.086 ± 0.041(stat) ± 0.030(sys) 0.03 < Sin 2 2  13 < 0.28 @ 90%C.L. for NH 0.04 < Sin 2 2  13 < 0.34 @ 90%C.L. for IH

73. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 73 Reactor Experiment: comparing observed/expected neutrinos Precision of past exp. n Reactor power: ~ 1% n Spectrum: ~ 0.3% n Fission rate: 2% n Backgrounds: ~1-3% n Target mass: ~1-2% n Efficiency: ~ 2-3% Typical precision: 3-6% Our design goal ： a precision of ~ 0.4%

74. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 74 Automatic Calibration System n Three Z axis: –One at the center »For time evolution, energy scale, non-linearity… –One at the edge »For efficiency, space response –One in the  -catcher »For efficiency, space response n 3 sources for each z axis: –LED »for T 0, gain and relative QE – 68 Ge (2  0.511 MeV  ’s) »for positron threshold & non-linearity… – 241 Am- 13 C + 60 Co (1.17+1.33 MeV  ’s) »For neutron capture time, … »For energy scale, response function, … n Once every week: –3 axis, 5 points in Z, 3 sources 2015-5-20 74

75. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 75 Flashers: Imperfect PMTs n Spontaneous light emission by PMT n ~ 5% of PMT, 5% of event n Rejection: pattern of fired PMTs –Topology: a hot PMT + near-by PMTs and opposite PMTs FlashersNeutrinos Quadrant = Q3/(Q2+Q4) MaxQ = maxQ/sumQ Inefficiency to neutrinos: 0.024%  0.006%(stat) Contamination: < 0.01%

76. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 76 Accidental Backgrounds EH1-AD1EH1-AD2EH2-AD1EH3-AD1EH3-AD2EH3-AD3 Rate(/day)9.82±0.069.88±0.067.67±0.053.29±0.033.33±0.033.12±0.03 B/S1.37%1.38%1.44%4.58%4.77%4.43% Simple calculation:

77. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 77 241 Am- 13 C Backgrounds n Uncorrelated backgrounds: R = 50 Hz  200  s  R n-like (events/day/AD) –R n-like Measured to be ~230/day/AD, in consistent with MC Simulation –R is not a negligible amount, particularly at the far site (B/S ~ 3.17%) –Measured precisely together with all the other uncorrelated backgrounds n Correlated backgrounds: –Neutron inelastic scattering with 56 Fe + neutron capture on 57 Fe –Simulation shows that correlated background is 0.2 events/day/AD, corresponding to a B/S ratio of 0.03% at near site, 0.3% at far site Uncertainty: 100%

78. Manfred Jeitler Daya Bay Neutrino Experiment Hephy, 19 October 2012 78  2 Analysis No constrain on absolute normalization. Fit on the near- far relative measurement.