The Daya Bay Anti-neutrino Experiment

Transcription

1 The Daya Bay Anti-neutrino Experiment On behalf on the Daya Bay Collaboration Jianglai Liu Shanghai Jiao Tong University KPS-CPS joint session, KPS annual meeting, Busan,

2 13 in PMNS Matrix U PMNS 32 o cos12 sin12 sin12 cos cos 0 13 sin e 13 i sin e 13 0 cos i 13 sin 0 cos sin23 cos o m 2 13 ~m 2 23 = ev 2 : CP Violation Phase m 2 12 ~ ev 2 2

3 Current Knowledge on 13 Upper limit from reactors Evidence from accelerators 3 non-zero from global analysis T2K collaboration 2011 Phys. Rev. Lett Allowed Region sin < 0.17 (90% c.l.) Fogli et al., arxiv: Chooz collaboration, Eur. Phys. J. C. 27 ( ), MINOS collaboration 2011 arxiv: v1 3

4 Lesson Learned in History: 3Discovery Phys. Lett. B 148: , Need definitive answer from other experiments! 13.6 m 18.3 m 4

5 Recent Excitement in Reactor Neutrino Disappearance A near-far relative measurement of reactor neutrino disappearance remains to be an unambiguous measurement of 13 Thierry Lasserre, TAUP P dis sin 2 sin (1.27m L ) E 5

6 Daya Bay An Ideal Location Powerful reactor (top 5 in the world, 17.4GW th ) by mountains Daya Bay Daya Bay NPP 2.9GW2 LingAo NPP 2.9GW2 LingAo II NPP 2.9GW2 6

7 Daya Bay Collaboration Europe (3) JINR, Dubna, Russia Kurchatov Institute, Russia Charles University, Czech Republic North America (16) BNL, Caltech, LBNL, Iowa state, Illinois Inst. Tech., Princeton, RPI, Siena Coll. UC-Berkeley, UCLA, U- Cincinnati, U-Houston, U-Wisconsin, Virginia Tech., U-Illinois-Urbana- Champaign, W&M ~ 250 collaborators Asia (19) IHEP, Beijing Normal Univ., Chengdu UST, CGNPG, CIAE, Dongguan Univ. of Tech., Nanjing Univ.,Nankai Univ., Shenzhen Univ., Shandong Univ.,Shanghai Jiaotong Univ., Tsinghua Univ., USTC, Zhongshan Univ., Hong Kong Univ., Chinese Hong Kong Univ., Taiwan Univ., Chiao Tung Univ., National United Univ. 7

8 4 x 20 tons target mass at far site Daya Bay: Powerful reactor by mountains Far site (Hall 3) 1615 m from Ling Ao 1985 m from Daya Overburden: 350 m Ling Ao Near site (Hall 2) 481 m from Ling Ao 526 m from Ling Ao II Overburden: 112 m Water hall Liquid Scintillator hall entrance SAB Construction tunnel Ling Ao NPP, 2x2.9 GW Daya Bay Near site (Hall 1) 363 m from Daya Bay Overburden: 98 m Ling Ao-ll NPP 2x2.9 GW Total Tunnel length ~ 3000 m Daya Bay NPP, 2x2.9 GW

9 Experimental Hall Overview experimental hall PMTs RPCs water pool muon veto system Multiple identical anti-neutrino detector modules Hall 1, Hall 2, Hall 3) Redundant muon detector: inner/outer water Cerenkov detectors + resistive plate chamber 9

10 Detection of Reactor Neutrinos Inverse Beta Decay e p n e Coincidence signal: detect Prompt: e + annihilation E v =KE e MeV Delayed: n capture on proton (2.2 MeV) or Gd (8 MeV) 10

11 Design of Anti-neutrino Detector (AD) Cylindrical 3-zone Structure Separated By Acrylic Vessels: I.Target: 0.1% Gd-loaded liquid scintillator, radius=half height= 1.55 m, 20 ton II. Gamma-catcher: liquid scintillator, 42.5 cm thick III. Buffer shielding: mineral oil, 48.8 cm thick Acyrlic vessel thickness: 1.5 cm (outer) and 1 cm (inner) PMT s on circumference and reflective reflectors on top and bottom. 12% energy resolution at 1 MeV 11

12 Expected Neutrino Signals Prompt Energy Signal 1 MeV Monte Carlo Delayed Energy Signal Near sites ~700/day/detector Far site ~90/day/detector Monte Carlo 6 MeV 10 MeV 12

13 Projected Uncertainty stat = 0.18% (4 far detector modules) Projected Sys Per Module 13

14 Suppression of Major Systematic Uncertainty N N f n N N p, f p, n L L n f 2 f n P P survival survival ( E, L ( E, L f n ) ) sin Number of Proton Ratio 0.3% Common Batch of liquid + precise flow & mass measurement Detector Efficiency Ratio 0.2% Calibrate out the near/far difference Identical Detectors Calibration, Calibration, Calibration! Side note: We blind true target masses, reactor power, and baselines to analyzer. 14

15 Calibration R=1.775 m R=0 R=1.35m Automated Calibration 3 sources for each z axis on a turntable: 68 Ge (0 KE e + = MeV s) 241 Am- 13 C neutron source + 60 Co gamma source LED source for T 0, gain and relative QE 15

16 Projected Sensitivity 3 Years, 90% Confidence Level 1 Year Of Data Taking = 300 Days 16

17 Daya Bay in Action 17

18 AD Assembly SSV Bottom reflector 4m AV Top reflector PMT 3m AV SSV lid Leak check ACU 18

19 Interior of AD 19

20 Dry Run of the First Pair of AD Complete test of assembled ADs with final electronics, trigger and DAQ 20

21 Daya Bay Liquid Scintillator Monitoring of Gd-LS in underground storage tanks 0.1% Gd-LS in 5000L tank Gd-LS produced in 50, 4-ton batches but mixed in reservoir onsite to ensure identical detectors. Gd-LS stability for > 450 days. Daya Bay experiment uses 185 ton 0.1% gadolinium-loaded liquid scintillator (Gd-LS). Gd-TMHA + LAB + 3g/L PPO + 15mg/L bis-msb 21

22 AD Filling Requirement: precision mass, equal liquid level and tem., chemical compatibility, Liquid extracted from common 200 ton tanks Detectors are filled in pairs First two pairs of ADs have been filled 22

23 Hall 1 Water Pool Installation 23

24 Installed Detectors in Hall 1 24

25 Hall 1 Water Pool Filling in air in water Clear demonstration of the water shielding effect. 25

26 Filled Pool in Hall 1 26

27 Hall 1 Ready for Data 27

28 Hall 1 Live Time 28

29 Hall 1 Am-C Source at Center of AD Proton recoil spectrum in AD Neutroncapture energy spectrum Neutron capture time Preliminary 29

30 Hall 1 Muon Rate Preliminary Preliminary AD1 AD2 Inner Pool Outer pool ~16hours ~16hours 30

31 Hall 2 Installation 31

32 Hall 3 Getting Ready for AD 32

33 Status and Prospects Daya Bay has finished 4 out of 8 ADs AD5 and 6 assembly nearly finish AD7 and 8 completion in spring 2012 Hall 1 taking data since Aug 2011 Hall 2 being installed Hall 3 getting ready for installation Summer 2012, data taking with full experiment 33

34 Stay Tuned for the Excitement! 34