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Results from Daya Bay

Results from Daya Bay. Xin Qian On behalf of Daya Bay Collaboration. Design goal for systematic 0.2~0.4% (relative) The largest, deepest reactor Θ 13 experiment in Town, aimed for sin 2 2 θ 13 <0.01 @ 90% C. L. Key to reach 0.01.

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Results from Daya Bay

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  1. Results from Daya Bay Xin Qian On behalf of Daya Bay Collaboration Xin Qian, BNL

  2. Design goal for systematic 0.2~0.4% (relative) The largest, deepest reactor Θ13 experiment in Town, aimed for sin22θ13 <0.01 @ 90% C. L. Xin Qian, BNL

  3. Key to reach 0.01 • (Stat) Powerful reactors (17.6 GW) +Large Mass (80 ton) • (Sys) Reactor related: using near/far to form ratio + baseline (near ~0.4 km, far ~1.7 km) • (Sys) Detector related: “identical detectors” + “precise detector calibration” • (Sys) Background related: deep underground to reduce cosmic + active/passive shielding Distances from reactor Far/Near νe Ratio Oscillation deficit Detector efficiency Detector Target Mass Xin Qian, BNL

  4. The Daya Bay Collaboration ~230 collaborators Xin Qian, BNL 4

  5. Daya Bay Anti-νe Detector Automated calibration system Reflectors at top/bottom of cylinder Effective photo-cathode coverage ~12% 192 Photomultipliers on the surrounding wall Steel tank 40 ton mineral oil (Shielding) Inneracrylic tank 20 ton Gd-loaded liquid scintillator (Target) Outeracrylic tank 22 ton liquid scintillator (gamma catching) 5 m diameter Xin Qian, BNL

  6. Muon Veto System Dual tagging systems: 2.5 meter thick two-section water shield and Resistance Plate Chambers (RPC) AD: Anti-neutrino Detector Two Zone ultrapure water Cherenkov detector Xin Qian, BNL

  7. Uncertainty Budgets Really small background contamination! Detector related: 0.12% (energy calibration) + ~0.1% (Gd capture ratio) + … Reactor related: 0.8%  ~0.04% in ratio Xin Qian, BNL

  8. The Hunting Race for θ13 Since 2011 2011 March 2012, Daya Bay reported the discovery of non-zero value of θ13 with a statistical significance > 5σ 2013 Xin Qian, BNL

  9. Spectral Oscillation Normal Inverted m32 |Δm2ee| Due to the short baseline, Daya Bay can observe one effective |Δm2ee|, which is is a constant shift of |Δm232| for two mass hierarchies m22 m22 m12 m12 |Δm2ee| m32 +(-) for Normal (Inverted) Mass Hierarchy Monte Carlo Unoscillated Oscillated We can also measure |Δm2ee| thanks to the “large” θ13 Xin Qian, BNL

  10. IBD Prompt Spectra • Clear observation of spectral distortion • Agree with 3-neutrino oscillation hypothesis Xin Qian, BNL

  11. Rate and Spectral Analysis Consistent with the MINOS result MINOS (νμ disappearance) Daya Bay (νe disappearance) Normal Inverted Xin Qian, BNL A.Radovic, DPF2013

  12. Current Status and Upcoming Results n-H rate-only results 8% improvement with nGd Compiled with latest results Results to be reported at Neutrino 14 and ICHEP: 1. Oscillation results with ~ 4 x data 2. Light sterile neutrino search with spectral distortion 3. Absolute reactor flux … Xin Qian, BNL

  13. Search for Light Sterile Neutrino Claims from cosmology e.g. arXiv:1403.7028 • Effects of sterile neutrino would appear as additional spectral distortion and overall rate deficit • Unique feature of Daya Bay with multiple baseline • Can probe largely unexplored region at Xin Qian, BNL

  14. Absolute Normalization Projection • Reactor, LSND, Gallium anomalies  ~ eV sterile neutrino ??? • Daya Bay can provide new information at ~ 360 m • Currently ~ 2.2% • Goal to reach < 1% in the future • U235, Pu239, Pu241 from Huber PRC84,024617 • U238 from Mueller et al. PRC83,054615 • Also A. C. Hayes et al. arXiv:1309.4146“… forbidden transitions can lead to antineutrino spectra that differ both in shape and magnitude at ~ 4% level” Reactor Anomaly Xin Qian, BNL

  15. Precision Measurement Phase sin22θ13 Δm2ee Combination of n-Gd and n-H with anticipated systematics improvements(sin22θ13 =0.09, Δm2ee =2.41e-3 eV2) The most precise measurement of sin22θ13for the foreseeable future Xin Qian, BNL

  16. Summary • We now determined θ13 • Large value of θ13 opens doors to study mass hierarchy, leptonic CP phase … • JUNO , LBNE, Hyper-K, LBNO … • We enter the precision era of neutrino physics • Exciting decades to come! Xin Qian, BNL

  17. Xin Qian, BNL

  18. Xin Qian, BNL

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