Daya Bay Reactor Neutrino Oscillation Experiment Jen-Chieh Peng - - PowerPoint PPT Presentation

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Daya Bay Reactor Neutrino Oscillation Experiment

Jen-Chieh Peng International Workshop on “Double Beta Decay and Neutrinos” Osaka, Japan, June 11-13, 2007

University of Illinois at Urbana-Champaign (on behalf of the Daya Bay Collaboration)

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Outline

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Physics case for a precise measurement The proposed Daya Bay neutrino oscillation experiment Schedule and expected sensitivity of the Daya Bay experiment θ

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What we have learned from neutrino

• scillation experiments

2 2 2 5 2 21 2 1 2 2 2 3 2 32 3 2 e 12 13 12 13 13 12 23 12 2

(7.9 0.7) 10 ev (90%c.l.) | | | | (2.4 0.6) 10 1) Neutrinos are massive 2) Neutrinos do mix with each ot ev (90% ) e c.l. h r

i

m m m m m m c c s c s e s c c s

δ µ τ

ν ν ν

− − −

∆ = − = ± × ∆ = − = ± ×     = − −      

1 3 13 12 23 12 23 13 23 13 2 12 23 12 23 13 12 23 12 23 13 23 13 3 12 23 3 3 1 1 12 2 3

( cos , sin ) 13 , 2. 34 , 45 , 13 for the l 2 , epton MNSP Matrix

i i i i ij ij ij ij

s e c c s s s e s c s s c c s e c s s c s e c c c s

δ δ δ δ

θ θ θ ν ν ν θ θ θ θ θ       −        − − −     = ≤ =

• 3) Neutrino masses and mixings have provided clear evidence for

physic .22 for the quark C s beyond the Stand KM Matrix ard Model

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What we do not know about the neutrinos

• Dirac or Majorana neutrinos?
• Mass hierachy and values of the masses?
• Existence of sterile neutrinos?
• Value of the θ13 mixing angle?
• Values of CP-violation phases?
• Origins of the neutrino masses?
• Other unknown unknowns …..

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What we know and do not know about the neutrinos

e 12 13 12 13 1 12 23 12 23 12 23 12 23 23 13 2 12 23 12 23 12 23 13 13 12 23 23 1 3 3 1 13 13 3 i i i i i

s e s e s e s c c s c s c c s c c s s s c s s c c c s e s c c e s c

µ δ δ δ δ δ τ

ν ν ν ν ν ν

−

            = − − −             − − −      

• What is the νe fraction of ν3?

(proportional to sin2θ13)

• Contributions from the CP-phase

δ to the flavor compositions of neutrino mass eigenstates depend

• n sin2θ13)

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Why measuring θ13?

A measurement of sin22θ13 at the sensitivity level of 0.01 can rule out at least half of the models!

• Models based on the

Grand Unified Theories in general give relatively large θ13

• Models based on

leptonic symmetries predict small θ13

A recent tabulation of predictions of 63 neutrino mass models on sin2θ13 (hep-ph/0608137)

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Why measuring θ13?

A measurement of sin22θ13 AND the mass hierarchy can rule out even more models!

A recent tabulation of predictions of 63 neutrino mass models on sin2θ13 (hep-ph/0608137)

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Why measuring θ13?

Leptonic CP violation

2 12 12 13 13 23 23 2 2 2 13 23 12

( ) ( ) 16 sin sin sin sin 4 4 4

e e

P P s c s c s c m m m L L L E E E

µ µ

ν ν ν ν δ → − → = −       ∆ ∆ ∆             If sin22θ13 > 0.02-0.03, then NOvA+T2K will have good coverage on CP δ. Size of sin22θ13 sets the scale for future leptonic CP violation studies

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Current Knowledge of θ13

• ∆

× −

θ13

• !
• θ

θ θ θ

"#$%#∆

&× −

θ θ θ θ

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decay pipe horn absorber target p detector

π+ π+ µ+

'())*+ '(,)*+

• µ ≈ θ θ ∆
• .

&* ν         +

• ≈ − θ ∆
• .

&* ν         + )& θ θ ∆

• .

&* ν        

/ ν → 0 )+ / 12345##)1%6 / $6) / νµ → ν )+ / ++)θ / 12345##) / +$

Some Methods For Determining θ13

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Detectingν : Inverse β Decay

ν + → 7 7 35 → 7→ 8 7γ3'5365 → 79 → 9: → 9 7γ;3!'5365 / < 6 %1)4%$ / *6#ν $16( *ν ≈ <7 7< 73 577≈ <7 7!'

&4

/ <)$β

β β β)6 =9>%

)(

Eν (MeV) 2 3 4 5 6 7 8 9 10

Arbitrary

F l u x Cross Section Observable ν Spectrum

From Bemporad, Gratta and Vogel

1 1

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Measuring θ13 with Reactor Neutrinos

Search for θ13 in new oscillation experiment

~1-1.8 km > 0.1 km

2 4 2 2 21 13 2 2 2 31 13 12

cos sin 2 sin 2 si sin 4 1 n 4

ee

m L E m P L E

ν ν

θ θ θ   ∆    ∆ −     ≈    −

θ θ θ θ13

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 0.1 1 10 100

Nosc/Nno_osc Baseline (km) Large-amplitude

• scillation due to θ12

Small-amplitude oscillation due to θ13 integrated over E

∆ ∆ ∆ ∆m2

13≈

≈ ≈ ≈ ∆ ∆ ∆ ∆m2

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detector 1 detector 2

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Results from Chooz

=9>%) )ν7→ 7 7 .4 8

• !&9?

,( @$63#%5 )% &146

@ν ) 3)%=145 6

A6)%)

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• Increase statistics:

– Use more powerful nuclear reactors – Utilize larger target mass, hence larger detectors

• Suppress background:

– Go deeper underground to gain overburden for reducing cosmogenic background

• Reduce systematic uncertainties:

– Reactor-related:

• Optimize baseline for best sensitivity and smaller reactor-related errors
• Near and far detectors to minimize reactor-related errors

– Detector-related:

• Use “Identical” pairs of detectors to do relative measurement
• Comprehensive program in calibration/monitoring of detectors
• Interchange near and far detectors (optional)

How to Reach a Precision of 0.01 in sin22θ13?

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World of Proposed Reactor Neutrino Experiments

Angra, Brazil Diablo Canyon, USA Braidwood, USA Chooz, France Krasnoyasrk, Russia Kashiwazaki, Japan RENO, Korea Daya Bay, China

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Location of Daya Bay

/ &4# AB / 4# CD

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!!"##$ × × × × % &'(() "##$ × × × × % (*("##$ × × × × %

9? × νe )

The Daya Bay Nuclear Power Complex

/ #% 3 9?5 / ##%163& 9?5 / E)%6 )%)%) %%1%##) $1%%))6

18 ( *( "## "## ) "## +'

,-.( )($%% %))% /' )(1 %%$B%

<(@

0-

1

• 2
• ( *("

#86 "6 2$1%(F! " @#. 2$1%( / #. F!#86 2$1%(

• /

3' !#. #86 2$1%(!

+ +

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Conceptual design of the tunnel and the Site investigation including bore holes completed

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Tunnel construction

• The tunnel length is about 3000m
• Local railway construction company has a lot of experience

(similar cross section)

• Cost estimate by professionals, ~ 3K $/m
• Construction time is ~ 15-24 months
• A similar tunnel on site as a reference

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Antineutrino Detectors

• Three-zone cylindrical detector design

– Target zone, gamma catcher zone (liquid scintillator), buffer zone (mineral oil) – Gamma catcher detects gamma rays that leak out

• 0.1% Gd-loaded liquid scintillator as

target material

– Short capture time and high released energy from capture, good for suppressing background

• Eight ‘identical’ detector modules, each with 20 ton

target mass

– ‘Identical’ modules help to reduce detector-related systematic uncertainties – Modules can cross check the performance of each other when they are brought to the same location

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• !"#

$%&'()*!+#,-# )$!./0 *$$1)-#

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Detector Prototype at IHEP

• 0.5 ton prototype

(currently unloaded liquid scintillator)

• 45 8” EMI 9350 PMTs:

14% effective photocathode coverage with top/bottom reflectors

• ~240 photoelectron

per MeV : 9%/√E(MeV)

prototype detector at IHEP

Energy Resolution

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Background Sources

• 1. Natural Radioactivity: PMT glass, steel, rock,

radon in the air, etc

• 2. Slow and fast neutrons produced in rock &

shield by cosmic muons

• 3. Muon-induced cosmogenic isotopes: 8He/9Li

which can β β β β-n decay

• Cross section measured at CERN (Hagner et. al.)
• Can be measured in-situ, even for near detectors

with muon rate ~ 10 Hz

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• F!
• !

Cosmic-ray Muon

/ G#9 B #))6#%+%#) / 6'GAHI%#% 6J6

138 97 60 55 Mean Energy (GeV) 0.041 0.17 0.73 1.16 Muon intensity (Hz/m2) 355 208 112 98 Overburden (m) Far Mid Ling Ao DY B

( *( / 3'

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Muon System

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Water Shield

• Pool around the central detectors - 2.5m water in all directions.
• Side, bottom & AD surfaces are reflective (Tyvek or equivalent)
• Outer shield is optically separated 1m of water abutting sides and bottom
• f pool

– PMT coverage ~1/6m2 on bottom and on two surfaces of side sections

• Inner shield has ≥1.5m water buffer for AD’s in all directions but up,

there the shield is 2.5m thick

– 8” PMTs 1 per 4m2 along sides and bottom - 0.8% coverage

Far Hall

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Muon System Active Components

• Inner water shield

–

415 8” PMTs

• Outer water shield

– 548 8” PMTs

• RPCs

– 756 2m × 2m chambers in 189 modules – 6048 readout strips

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Summary of Systematic Uncertainties

0.32% (Daya Bay near) 0.22% (Ling Ao near) 0.22% (far) Backgrounds 0.2% Signal statistics 0.38% (baseline) 0.18% (goal) Detector (per module) 0.087% (4 cores) 0.13% (6 cores) Reactors Uncertainty sources

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(hep-ex/0701029) Daya Bay Conceptual Design Report