Results from Daya Bay Xin Qian On behalf
Results from Daya Bay Xin Qian On behalf of Daya Bay Collaboration Xin Qian, BNL 1
Design goal for systematic 0. 2~0. 4% (relative) The largest, deepest reactor Θ 13 experiment in Town, aimed for sin 22θ 13 <0. 01 @ 90% C. L. Xin Qian, BNL 2
Key to reach 0. 01 • (Stat) Powerful reactors (17. 6 GW) +Large Mass (80 ton) Far/Near νe Ratio Distances from reactor Detector Target Mass Oscillation deficit Detector efficiency • (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 Xin Qian, BNL 3 reduce cosmic + active/passive shielding
The Daya Bay Collaboration ~230 collaborators Xin Qian, BNL 4 4
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) Inner acrylic tank 20 ton Gd-loaded liquid scintillator (Target) Outer acrylic tank 22 ton liquid scintillator (gamma catching) Xin Qian, BNL 5 m diameter 5
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 6
Uncertainty Budgets Backgrounds Near Accidental ACU-N ~1. 7% ~0. 04% Far + systematic uncertainties ~4. 6% + negligible sys. ~0. 36% + 50% relative sys Li 9/He 8 Fast-N Alpha-N ~0. 35% ~0. 14% ~0. 01% ~0. 3% + 24% relative sys ~0. 05% + 50% relative sys 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 7
The Hunting Race for θ 13 Since 2011 March 2012, Daya Bay reported the discovery of non-zero value of θ 13 with a statistical significance > 5σ 2013 Xin Qian, BNL 8
Spectral Oscillation m 32 Due to the short baseline, Daya Bay can observe one effective |Δm 2 ee|, which is is a constant shift of |Δm 232| for two mass hierarchies Normal Inverted |Δm 2 ee| m 22 m 12 |Δm 2 ee| +(-) for Normal (Inverted) Mass Hierarchy m 32 Monte Carlo Unoscillated Oscillated We can also measure |Δm 2 ee| thanks to the “large” θ 13 Xin Qian, BNL 9
IBD Prompt Spectra • Clear observation of spectral distortion • Agree with 3 -neutrino oscillation hypothesis Xin Qian, BNL 10
Rate and Spectral Analysis Consistent with the MINOS result Daya Bay (νe disappearance) MINOS (νμ disappearance) Normal Inverted Xin Qian, BNL A. Radovic, DPF 2013 11
Current Status and Upcoming Results n-H rate-only results 8% improvement with n. Gd 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 … 12
Search for Light Sterile Neutrino Claims from cosmology e. g. ar. Xiv: 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 13
Absolute Normalization Projection • Reactor, LSND, Gallium anomalies ~ e. V sterile neutrino ? ? ? • Daya Bay can provide new information at ~ 360 m • Currently ~ 2. 2% • Goal to reach < 1% in the future • U 235, Pu 239, Pu 241 from Huber PRC 84, 024617 • U 238 from Mueller et al. PRC 83, 054615 • Also A. C. Hayes et al. ar. Xiv: 1309. 4146 “… forbidden transitions can lead to antineutrino spectra that differ both in shape and magnitude at ~ 4% level” Reactor Anomaly Xin Qian, BNL 14
Precision Measurement Phase sin 22θ 13 Δm 2 ee Combination of n-Gd and n-H with anticipated systematics improvements (sin 22θ 13 =0. 09, Δm 2 ee =2. 41 e-3 e. V 2) The most precise measurement of sin 22θ 13 Xin Qian, BNL for the foreseeable future 15
Summary • We now determined θ 13 • Large value of θ 13 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 16
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