Results from Daya Bay Xin Qian On behalf of Daya Bay Collaboration Xin Qian, BNL1.
Transcript of Results from Daya Bay Xin Qian On behalf of Daya Bay Collaboration Xin Qian, BNL1.
Xin Qian, BNL 1
Results from Daya Bay
Xin QianOn behalf of Daya Bay Collaboration
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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.
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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 νe Ratio
Detector Target Mass
Distances from reactor
Detector efficiency
Oscillation deficit
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The Daya Bay Collaboration
4
~230 collaborators
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Daya Bay Anti-νe Detector
192 Photomultipliers on the surrounding wall
Outer acrylic tank22 ton liquid scintillator (gamma catching)
Automated calibration system
Inner acrylic tank20 ton Gd-loaded liquid scintillator (Target)
Steel tank40 ton mineral oil (Shielding)
Reflectors at top/bottom of cylinderEffective photo-cathode coverage ~12%
7.5( 0.9)%
( )
E
E E MeV
5 m diameter
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Muon Veto SystemDual 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
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Uncertainty BudgetsBackgrounds Near Far + 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
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The Hunting Race for θ13 Since 20112011
2013
March 2012, Daya Bay reported the discovery of non-zero value of θ13 with a statistical significance > 5σ
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∣ Δ𝑚𝑒𝑒2 ∣≈ ∣Δ𝑚32
2 ∣±5.21×10− 5𝑒𝑉 2
Due to the short baseline, Daya Bay can observe one effective |Δm2
ee|, which is is a constant shift of |Δm2
32| for two mass hierarchies
Monte Carlo
UnoscillatedOscillated
Spectral Oscillation
𝑃 ( ν̄𝑒→ν̄ 𝑒)≈1−sin22θ13sin2(1.27 Δ𝑚𝑒𝑒2 𝐿𝐸 )
|Δm2ee|
+(-) for Normal (Inverted) Mass Hierarchy
Normal Inverted
|Δm2ee|
m12
m22
m32
m12
m22
m32
5.21×10− 5𝑒𝑉 2
We can also measure |Δm2ee| thanks to the “large” θ13
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IBD Prompt Spectra
• Clear observation of spectral distortion
• Agree with 3-neutrino oscillation hypothesis
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Rate and Spectral Analysis 𝐬𝐢𝐧𝟐𝟐𝛉𝟏𝟑=𝟎 .𝟎𝟗𝟎−𝟎.𝟎𝟎𝟗+𝟎 .𝟎𝟎𝟖
∣𝚫𝐦𝑒𝑒𝟐 ∣=𝟐 .𝟓𝟗−𝟎 .𝟐𝟎
+𝟎.𝟏𝟗×𝟏𝟎−𝟑 (𝑒𝑉 𝟐 )
𝚫𝐦𝟑𝟐𝟐 =𝟐 .𝟓𝟒−𝟎 .𝟐𝟎
+𝟎 .𝟏𝟗 ×𝟏𝟎−𝟑 (𝑒𝑉 𝟐 )
𝚫𝐦𝟑𝟐𝟐 =−𝟐 .𝟔𝟒−𝟎.𝟐𝟎
+𝟎 .𝟏𝟗×𝟏𝟎−𝟑 (𝑒𝑉 𝟐 )
χ 2/𝑁𝐷𝐹=162.7/153
𝚫𝐦𝟑𝟐𝟐 =𝟐 .𝟑𝟕−𝟎 .𝟎𝟗
+𝟎 .𝟎𝟗 ×𝟏𝟎−𝟑 (𝑒𝑉 𝟐)
𝚫𝐦𝟑𝟐𝟐 =−𝟐 .𝟒𝟏−𝟎.𝟎𝟗
+𝟎 .𝟏𝟏×𝟏𝟎−𝟑 (𝑒𝑉 𝟐 )
Normal
Inverted
A.Radovic, DPF2013
Consistent with the MINOS result
Daya Bay (νe disappearance) MINOS (νμ disappearance)
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Current Status and Upcoming Results n-H rate-only results
8% improvement with nGd
Compiled with latest results2
13sin 2 0.083 0.018n H
Results to be reported at Neutrino 14 and ICHEP:1. Oscillation results with ~ 4 x data 2. Light sterile neutrino search with spectral distortion3. Absolute reactor flux…
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Search for Light Sterile Neutrino
2 24 2 2 2 2 41
14 13 14( ) 1 cos sin 2 sin sin 2 sin4 4ee
e em L m L
PE E
• 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 2 241 0.1 m eV
Claims from cosmologye.g. arXiv:1403.7028
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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 PRC84,024617
• 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”
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Precision Measurement Phase
Combination of n-Gd and n-H with anticipated systematics improvements(sin22θ13 =0.09, Δm2
ee =2.41e-3 eV2)
The most precise measurement of sin22θ13 for the foreseeable future
sin22θ13 Δm2ee
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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!
2 0.00813 0.009
2 0.20 3 20.19
Daya Bay: sin 2 0.090
| | 2.59 10 eVeem
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