第十六届核电子学与核探测技术学术年会, 2012年8月 1

Daya Bay Reactor Neutrino ExperimentLatest Results and Its Future

李小男

核探测与核电子学国家重点实验室

高能物理研究所

第十六届核电子学与核探测技术学术年会, 2012年8月 2

Two HEP Events in 2012Non-Zero θ13 Discovery

2012.7.4

Higgs “Discovery”

•sin22θ13=0.092±0.016(stat)±0.005(syst)

第十六届核电子学与核探测技术学术年会, 2012年8月 3

World Applauded

第十六届核电子学与核探测技术学术年会, 2012年8月 4

曹俊的总结

Neutrino Oscillation• Neutrino Mixing: PMNS Matrix

13 113

13 13

2 12

12 123 2 23

23 23

cos 0 si1 0 00 cos s

n0 1 0

cos sin 0sin cos 0

sinin

0 0sin cos 00 cos 1

i

i

e

e

Atmospheric, K2K, MINOS, T2K, etc.

23 ~ 45º

SolarKamLAND12 ~ 30º

ReactorAccelerator13 < 12º

•Known: |m232|, sin2223, m2

21, sin2212

•Unknown: sin2213, CP, Sign of m232

•Daya Bay experiment is designed to measure sin22θ13 to 0.01 or better at 90% C.L. in a three-year run.

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Direct Searches in the Past• Palo Verde & CHOOZ: no signal

• T2K: 2.5 over bkg

• MINOS: 1.7 over bkg

• Double Chooz: 1.7

•Allowed region

Sin2213 < 0.12 @ 90%C.L. if M2

23 = 0.0024 eV2

0 < Sin2213 < 0.12 @ 90%C.L. NH0 < Sin2213 < 0.19 @ 90%C.L. IH

sin22θ13 = 0.086 ± 0.041(stat) ± 0.030(sys)

0.03 < Sin2213 < 0.28 @ 90%C.L. for NH0.04 < Sin2213 < 0.34 @ 90%C.L. for IH

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Global fit 3Fogli et al)No single exp. exceeds 3

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Daya Bay Experiment: Layout

• Relative measurement to cancel Corr. Syst. Err. – 2 near sites, 1 far site

• Multiple AD modules at each site to – Far: 4 modules，near: 2 modules

• Multiple muon detectors to reduce veto eff. uncertainties– Water Cherenkov： 2 layers – RPC： 4 layers at the top + telescopes

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Verify Uncorr. syst. Err.Reduce Uncorr. Syst. Err.

Underground Labs

Overburden（MWE）

R（Hz/m2）

E（GeV）

D1,2(m)

L1,2(m)

L3,4(m)

EH1 250 1.27 57 364 857 1307EH2 265 0.95 58 1348 480 528EH3 860 0.056 137 1912 1540 1548

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•40 t MO

•20 t LS

•20 t Target

•reflector

•reflector

•Automated Calibration Units (ACU)

Anti-neutrino Detector (AD)

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•Target: 20 t, 1.55m-catcher: 20 t, 45cm

•Buffer: 40 t, 45cm

•Total weight: ~110 t

Three zones modular structure: I. target: Gd-loaded scintillator-catcher: normal scintillatorIII. buffer shielding: oil

192 8” PMTs/module Two optical reflectors at the top

and the bottom, doubled the photocathode coverage.

Light yield: ~163 PE/MeV

第十六届核电子学与核探测技术学术年会, 2012年8月 11

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nepe

•10-40 keV

•Neutrino energy:

•Neutrino Event: coincidence in time, space and energy

epnne

mMMTTE )(

Neutrino Detection: Gd-loaded Liquid Scintillator

•1.8 MeV: Threshold

s(0.1% Gd)

•n + p d + (2.2 MeV)•n + Gd Gd* + (8 MeV)

13第十六届核电子学与核探测技术学术年会, 2012年8月

Gd-loaded Liquid Scintillator• Home made liquid:

– 185t Gd-LS, ~200t LS, ~320t oil

• LAB-based+PPO+BisMSB• Gd(TMHA)3• Stable over time

– IHEP prototype (600L) since 2007– 4-ton dry run since Mar. 2009– 185t production completed in Jan. 2011

•Liquid hall and mixing equipment

•Stable Liquid

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Automatic Calibration System • Three Z axis:

– One at the center• For time evolution, energy scale, non-

linearity… – One at the edge

• For efficiency, space response– One in the -catcher

• For efficiency, space response• 3 sources for each z axis:

– LED • for T0, gain and relative QE

– 68Ge (20.511 MeV ’s) • for positron threshold & non-linearity…

– 241Am-13C + 60Co (1.17+1.33 MeV ’s)• For neutron capture time, …• For energy scale, response function, …

• Once every week:– 3 axis, 5 points in Z, 3 sources

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Muon Veto Detector • Water Pool

– High purity de-ionized water in pools also for shielding (2.5m)

– First stage water production in hall 4

– Local water re-circulation & purification

• Water Cerenkov detector– Two layers, separated by

Tyvek/PE/Tyvek film– 288 8” PMTs for near halls– 384 8” PMTs for the far hall

• RPCs– 4 layers/module– 54 modules/near hall, 81

modules/far hall– 2 telescope modules/hall•Two active cosmic-muon veto’s

Water Cerenkov: Eff.>99.7% (long track muon) RPC Muon tracker: Eff. > 88%

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•Antineutrino Detector Installation - Near Hall

17第十六届核电子学与核探测技术学术年会, 2012年8月

Two ADs Installed in Hall 1

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Hall 1 (2 ADs) Started the Operation on Aug.15, 2011

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One AD installed in Hall 2 Physics Data Taking Started on Nov.5, 2011

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Three ADs installed in Hall 3Physics Data Taking Started on Dec.24, 2011

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•Hall 1

•Hall 2

•Hall 3

•A

•B

•C

• ATwo Detector Comparison: Sep. 23, 2011 – Dec. 23, 2011Nucl. Inst. and Meth. A 685 (2012), pp. 78-97

• BFirst Oscillation Result:Dec. 24, 2011 – Feb. 17, 2012Phys. Rev. Lett. 108, 171803 (2012)

• CUpdated analysis:Dec. 24, 2011 – May 11, 2012To be submitted to Chinese Physics C– Data volume: 40TB– DAQ eff. ~ 96%– Eff. for physics: ~ 94%

Data Period

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Anti-neutrino Events Selection

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• Prompt energy

• Delayed energy

• Good Agreement with MC

• Time between  prompt‐delayed 

• Anti-neutrino event selection– 0.7 MeV < Ep < 12.0 MeV– 6.0 MeV < Ed < 12.0 MeV– 1 μs < Δtp-d < 200 μs– Muon Veto: 0.6 ms after a Pool muon (reject fast

neutron), 1 ms after an AD muon (reject double neutron), 1 s after an AD shower muon (reject 9Li/8He)

– Multiplicity cut: No other >0.7 MeV trigger in (tp-200μs , td+200 μs)

Side-by-side Comparison• Expected ratio of neutrino events: R(AD1/AD2) = 0.982

– The ratio is not 1 because of target mass, baseline, etc.• Measured ratio: 0.987 0.004(stat) 0.003(syst)

•This check shows that systematic errors are under control, and will determine the final systematic error

•Data set: Dec 24 to May 11

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• 9Li yield

BackgroundsAccidentals

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9Li/8He

Fast Neutrons

ACU Am-C

•n-like singles

•Constrain fast-n rate using•IBD-like signals in 10-50 MeV

9Li9Li

Signals and Backgrounds

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AD1 AD2 AD3 AD4 AD5 AD6Antineutrino candidates

69121 69714 66473 9788 9669 9452

DAQ live time (day) 127.5470 127.3763 126.2646Efficiency m 0.8015 0.7986 0.8364 0.9555 0.9552 0.9547Accidentals (/day) 9.73±0.10 9.61±0.10 7.55±0.08 3.05±0.04 3.04±0.04 2.93±0.03

Fast neutron (/day) 0.77±0.24 0.77±0.24 0.58±0.33 0.05±0.02 0.05±0.02 0.05±0.028He/9Li (/day) 2.9±1.5 2.0±1.1 0.22±0.12Am-C corr. (/day) 0.2±0.213C(α, n)16O (/day) 0.08±0.04 0.07±0.04 0.05±0.03 0.04±0.02 0.04±0.02 0.04±0.02Antineutrino rate (/day)

662.47±3.00

670.87±3.01

613.53±2.69

77.57±0.85

76.62±0.85

74.97±0.84

•Target Protons Uncertainty

Efficiencies & Uncertainties

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•Design value•Baseline: 0.38%•Goal: 0.18%

Quantity Relative AbsoluteFree protons/kg neg. 0.47%

Density neg. 0.0002%

Total mass 0.015% 0.015%

Bellows 0.0025% 0.0025

Overflow tank 0.02% 0.02%

Total 0.03% 0.47%

•All detectors use one common batch of target scintillator

Reactor Neutrinos

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• Reactor neutrino spectrum

Relative measurement flux model has negligible impact on far v.s near oscillation measurement

•Kopeikin et al, Physics of Atomic Nuclei, Vol. 67, No. 10, 1892 (2004)

•neutrino spectra per fission of each isotope

•simulated fission rate

The measured thermal power Wth is used for normalization when simulating fission rate

•Energy release per fission

Daily Anti-neutrino Rate• Three halls taking data synchronously allows near-far

cancellation of reactor related uncertainties• Rate changes reflect the reactor on/off.

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•Predictions are scaled by a common absolute normalization factor from the fitting

•Via GPS and modern theodolites, relative detector-core positions are known to 3cm

Discovery of a non-zero value of 13

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•R = 0.940 ± 0.011 (stat) ± 0.004 (syst)

•A clear observation of far site deficit with the first 55 days’ data.•5.2 for non-zero value of 13•Spectral distortion consistent with oscillation.

•sin22θ13=0.092±0.016(stat)±0.005(syst)

Improved results

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•R = 0.944 ± 0.007 (stat) ± 0.003 (syst) •sin22θ13=0.089±0.010(stat)±0.005(syst)

•With 2.5x more statistics, an improved measurement to 13

Summary & Outlook

• Daya Bay has unambiguously observed reactor electron-antineutrino disappearance

• Interpreting the disappearance as neutrino oscillation yields the most precise measurement of 13:

• Install the last two antineutrino detectors this year, measure sin2213 to ~5% precision

• Persue other physics, such as precise reactor νe flux and spectrum, and measurement of m2

31 (~5% precision)

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R = 0.944 ± 0.007 (stat) ± 0.003 (syst)

sin22θ13 = 0.089 ± 0.010 (stat) ± 0.005 (syst)

第十六届核电子学与核探测技术学术年会, 2012年8月 33

Dayabay IIthe Next Generation

Reactor Neutrino Experiment

Other Scientific Goals1. Neutrino Mass hierarchy2. Precision measurement of mixing parameters: 12,

M212, M2

31 test the unitarity of the mixing matrix3. Supernova neutrinos4. Geo-neutrinos5. Exotics searches

1.Sterile neutrinos2.Monopoles, Fractional charged particles, ….

6. Target for neutrino beams7. Atmospheric neutrinos8. Solar neutrinos 9. High energy cosmic-rays & neutrinos

1.Point source: GRB, AGN, BH, …2.Diffused neutrinos3.Dark matter

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Daya Bay-II Experiment

•Daya Bay

•60 km•Daya Bay II

•KamLAND

20-50 kton LS detector 2-3 % energy resolution Rich physics possibilities

Mass hierarchy Precision measurement

of 4 mixing parameters Supernovae neutrino Geoneutrino Sterile neutrino Atmospheric neutrinos Exotic searches

•Talk by Y.F. Wang at ICFA seminar 2008, Neutel 2011; by J. Cao at Nutel 2009, NuTurn 2012 ; •Paper by L. Zhan, Y.F. Wang, J. Cao, L.J. Wen, PRD78:111103,2008; PRD79:073007,2009

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Site Candidate

•Daya Bay •New exp.

58 km58 km

128.9 km

Daya Bay NPP•6x2.9GW

Huizhou NPPplanned 6x2.9GW

Lufeng NPPplanned 6x2.9GW

•Overburden >1500 MWE

•Baseline Optimization for Mass Hierachy

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Mixing parameters

• Uncertainties of mixing parameters

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Current Daya Bay II

m212 3% < 1%

m223 5% < 1%

sin212 6% < 1%

sin223 20% -

sin213 20% (5%) cross check to 5%

Check the unitary of the mixing matrix to 1%(need sin223, CPV)

•To be elaborated

Supernova neutrinos• Less than 20 events observed so far• Assumptions:

– Distance: 10 kpc (our Galaxy center) – Energy: 31053 erg– L the same for all types– Tem. & energy

• Many types of events:e + p n + e+, ~ 3000 correlated eventse + 12C 13B* + e+, ~ 10-100 correlated eventse + 12C 11N* + e-, ~ 10-100 correlated eventsx + 12C ｘ+ 12C*, ~ 600 correlated eventsx + p ｘ+ p, single eventse + e- e + e-, single eventsx + e-ｘ+ e-, single events

•T(e) = 3.5 MeV, <E(e)> = 11 MeV•T(e) = 5 MeV, <E(e)> = 16 MeV•T(x) = 8 MeV, <E(x)> = 25 MeV

Water Cerenkov detectors can not see these correlated events

Energy spectra & fluxes of all types of neutrinos

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Geoneutrinos

• Current results:– KamLAND:

40.0±10.5±11.5 TNU– Borexino:

64±25±2 TNU• Desire to reach an error

of 3 TNU: statistically dominant

• Daya Bay II: >×10 statistics, but difficult on systematics

• Background to reactor neutrinos

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Stephen Dye

•Muon tracking

•Liquid Scintillator20 kt

•Acrylic sphere：φ34.5m

•SS sphere ： φ 37 .5m

•Water Seal

•~15000 20” PMTsoptical coverage: 70‐80%

•Stainless steel tank

•MO buffer6kt

•Water Buffer  10kt

Detector Concept

•Details to be worked out

• 20” VETO PMTs

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Technical Challenges• Requirements:

– Large detector: >10 kt LS– Energy resolution: 3%/E 1200 p.e./MeV

• Ongoing R&D:– Low cost, high QE “PMT”

• MCP-Based large Area PMT Collaboration– Highly transparent LS: 15m 30m

• Improve raw materials (using Dodecane instead of MO for LAB production）

• Improve the production process• Purification

KamLAND Daya Bay IILS mass ~1 kt 20 kt

Energy Resolution

6%/E 3%/E

Light yield 250 p.e./MeV 1200 p.e./MeV

A new type of PMT

•8”MCP-PMT

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第十六届核电子学与核探测技术学术年会, 2012年8月 42

End

Thanks

The Daya Bay Collaboration

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~250 Collaborators

•Europe (2)

•JINR, Dubna, Russia•Charles University, Czech Republic

•North America (16)

•BNL, Caltech, Iowa State Univ., •Illinois Inst. Tech., LBNL, Princeton, RPI, Siena,

UC-Berkeley, UCLA, Univ. of Cincinnati, •Univ. of Houston, Univ. of Wisconsin-Madison,

•Univ. of Illinois-Urbana-Champaign, •Virginia Tech., William & Mary

• Asia (20)

• Beijing Normal Univ., Chengdu Univ. of Sci. and Tech., CGNPG, CIAE, Dongguan Univ.Tech., IHEP,

• Nanjing Univ., Nankai Univ., NCEPU, Shandong Univ., • Shanghai Jiao tong Univ., Shenzhen Univ., • Tsinghua Univ., USTC, Zhongshan Univ.,

• Univ. of Hong Kong, Chinese Univ. of Hong Kong, • National Taiwan Univ., National Chiao Tung Univ.,

• National United Univ.