Results from Daya Bay Xin Qian On behalf of Daya Bay Collaboration Xin Qian, BNL1

Design goal for systematic 0.2~0.4% (relative) The largest, deepest reactor Θ 13 experiment in Town, aimed for sin 2 2θ 13 90% C. L. Xin Qian, BNL2

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 Far/Near ν e Ratio Detector Target Mass Distances from reactor Detector efficiency Oscillation deficit Xin Qian, BNL3

The Daya Bay Collaboration 4 ~230 collaborators Xin Qian, BNL4

Daya Bay Anti-ν e Detector 192 Photomultipliers on the surrounding wall Outer acrylic tank 22 ton liquid scintillator (gamma catching) Automated calibration system Inner acrylic tank 20 ton Gd-loaded liquid scintillator (Target) Steel tank 40 ton mineral oil (Shielding) Reflectors at top/bottom of cylinder Effective photo-cathode coverage ~12% 5 m diameter Xin Qian, BNL5

Muon Veto System Dual tagging systems: 2.5 meter thick two-section water shield and Resistance Plate Chambers (RPC) Two Zone ultrapure water Cherenkov detector AD: Anti-neutrino Detector Xin Qian, BNL6

Uncertainty Budgets BackgroundsNearFar + systematic uncertainties Accidental~1.7%~4.6% + negligible sys. ACU-N~0.04%~0.36% + 50% relative sys Li9/He8~0.35%~0.3% + 24% relative sys Fast-N~0.14%~0.05% + 50% relative Alpha-N~0.01%~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, BNL7

The Hunting Race for θ 13 Since March 2012, Daya Bay reported the discovery of non-zero value of θ 13 with a statistical significance > 5σ Xin Qian, BNL8

Due to the short baseline, Daya Bay can observe one effective |Δm 2 ee |, which is is a constant shift of |Δm 2 32 | for two mass hierarchies Monte Carlo Unoscillated Oscillated Spectral Oscillation |Δm 2 ee | +(-) for Normal (Inverted) Mass Hierarchy Normal Inverted |Δm 2 ee | m12m12 m22m22 m32m32 m12m12 m22m22 m32m32 We can also measure |Δm 2 ee | thanks to the “large” θ 13 Xin Qian, BNL9

IBD Prompt Spectra Clear observation of spectral distortion Agree with 3-neutrino oscillation hypothesis Xin Qian, BNL10

Rate and Spectral Analysis Normal Inverted A.Radovic, DPF2013 Consistent with the MINOS result Daya Bay (ν e disappearance) MINOS (ν μ disappearance) Xin Qian, BNL11

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, BNL12

Search for Light Sterile Neutrino 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 Claims from cosmology e.g. arXiv: Xin Qian, BNL13

Absolute Normalization Projection Reactor Anomaly 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, U238 from Mueller et al. PRC83, Also A. C. Hayes et al. arXiv: “… forbidden transitions can lead to antineutrino spectra that differ both in shape and magnitude at ~ 4% level” Xin Qian, BNL14

Precision Measurement Phase Combination of n-Gd and n-H with anticipated systematics improvements (sin 2 2θ 13 =0.09, Δm 2 ee =2.41e-3 eV 2 ) The most precise measurement of sin 2 2θ 13 for the foreseeable future sin 2 2θ 13 Δm 2 ee Xin Qian, BNL15

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, BNL16

Xin Qian, BNL17

Xin Qian, BNL18