Perspectives for the measurement of mass hierarchy with the Daya Bay II experiment

Changgen Yang Institute of High Energy Physics, Beijing

NuMass 2013, Milano, Italy 4-7 February 2013

Outline

Physics Plan and Challenges Detector concepts Signal & Backgrounds Site survey & civil Cost, Schedule and Status Summary

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The large θ13 era Non-zero and large θ13 observed and the sin22θ13 precision can

reach to 5% by Daya Bay in three years. Mass hierarchy and CP phase are the main focus of next

generation neutrino experiments. A medium baseline reactor neutrino experiment can measure

mass hierarchy independent of CP phase.

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Daya Bay, Dec 24, 2011 - May 11, 2012 sin22θ13 = 0.089 ± 0.010(stat) ± 0.005(sys)

NH IH

Reactor neutrino to determine MH

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S.T. Petcov et al., PLB533(2002)94 S.Choubey et al., PRD68(2003)113006 J. Learned et al., hep-ex/0612022 L. Zhan, Y. Wang, J. Cao, L. Wen, PRD78:111103, 2008 PRD79:073007, 2009

50000 events

Mass hierarchy：sensitivity

3 years 6 years

Thanks to a large θ13

∆M223

Fourier transformation:

Detector size: 20kt Energy resolution: 3%/√E Thermal power: 36 GW Baseline 58 km

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More Calculations and Considerations Improve MH sensitivity with χ2

method by taking into account ∆M2

23 from T2K and Nova in the future;

Reactor interference effects with different baselines;

Study of nonlinear energy response to the mass hierarchy determination;

Peak location with 2 detectors The oscillation frequencies with

2 identical detectors at 2 distinct baselines; etc

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Contribution from ∆M2

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Daya Bay-II Experiment

Daya Bay 60 km Daya Bay II

KamLAND

20 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

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The plan and Challenges: a large LS detector

20 kt LS

Inner tank：Φ34.5m Outer tank：Φ37.5m

Muon detector

Water seal

~15000 20” PMTs coverage: ~80%

Steel Tank

6kt MO

20kt water

1500 20” VETO PMTs

KamLAND Daya Bay II

LS mass ~1 kt 20 kt

Energy Resolution 6%/√E 3%/√E

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

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lectrons -- PMT

No clearance: coverage 86.5% 1cm clearance: coverage: 83%

20" + 8" PMT 8" PMT for better timing(vertex)

SBA photocatode

More Photons-- PMT

New type of PMT: MCP-PMT

Top: transmitted photocathode

Bottom: reflective photocathode

~ ×2 improvement

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A PMT R&D collaboration

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Main Player: North Night-vision Main product: MCP, image intensifier, …

Largest MCP producer in China, 30% world market

MCP production: 100k/year, image intensifier: 16k/year

Main Player: HZC Bought Photonics PMT division two years ago

Prototypes

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8”MCP-PMT Glass

HZC

More Photons-- LS Longer attenuation length Improve raw materials (using Dodecane

instead of MO for LAB production） Improve the production process Purification

Higher light yield Lower temperature fluor concentration optimization

Linear Alky Benzene

Atte. Length @ 430 nm

RAW 14.2 m Vacuum distillation 19.5 m

SiO2 coloum 18.6 m Al2O3 coloum 22.3 m

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,70,0

0,2

0,4

0,6

0,8

1,0

LIgh

t out

put,

rela

tive

units

PPO mass fraction, %

KamLAND

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Energy Resolution(MC) DYBII MC, based on DYB MC (tuned to data), except

DYBII Geometry and 80% photocathode coverage SBA PMT: maxQE from 25% -> 35% Lower detector temperature to 4 degree (+13% light) LS attenuation length (1m-tube measurement@430nm)

from 15m = absoption 24m + Raylay scattering 40 m to 20 m = absorption 40 m + Raylay scattering 40m

Uniformly Distributed Events

After vertex-dep. correction

R3 13

R3

Central Detector Concept

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Options： No steel tank, only

acrylic one Steel tank +

Acrylic box/wall Balloon nothing

Extremely difficult to build

both the stainless steel tank and the acrylic tank

Inner layer：~Φ34.5m Outer layer (SSV)：~Φ37.5m

VETO Detector Concept Water Cerenkov A MC simulation show that ~ 2m water, 1500 20”

PMT is good enough Top VETO Options:

RPC Plastic scintillator Liquid scintillator

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IBD Signal Signal:

LS without Gd-loading for Better attenuation length resolution Lower irreducible accidental backgrounds from LS,

important for a larger detector: With Gd: ~ 10 -12 g/g Without Gd: ~ 10 -16 g/g

Less risk

Longer capture time & lower energy the capture signal more accidental backgrounds

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τ ~ 200 µs

Estimated IBD rate: ~40/day

Backgrounds Summary

Assumptions Overburden is 700m

Eµ ~ 211 GeV, Rµ ~ 3.8 Hz Single rates from LS and PMT are

5Hz, respectively Good muon tracking Similar muon efficiency as DYB

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Daya Bay Daya Bay II Mass (ton) 20 20,000 Eµ (GeV) ~57 ~211 Rµ (Hz) ~21 ~3.8 Rsingles (Hz) ~50 ~10

B/S @ DYB EH1

B/S @ DYB II

Techniques used for DYB II detector

Accidentals ~1.4% ~10% Low PMT radioactivity; LS purification; prompt-delayed distance cut

Fast neutron

~0.1% ~0.4% High muon detection efficiency (similar as DYB)

9Li/8He ~0.4% ~0.8% Muon tracking; If good track, distance to muon track cut (<5m) and veto 2s; If shower muon, full volume veto 2s

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New site：Kaiping county, Jiangmen city

Daya Bay Huizhou Lufeng Yangjiang Taishan

Status running planned approved Construction construction power/GW 17.4 17.4 17.4 17.4 18.4

Daya Bay Huizhou

Lufeng

Previous site

Current site

Yangjiang Taishan

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Site selection Allowed region determined Experimental hall selected: In granite Mountain height: 270 m

Preliminary geological survey completed: Review held on Dec. 17, 2012 No show-stoppers

Detailed geological survey to be started soon

Contacts with local government established, good support 19

Construction plan Conceptual design completed. Review held on Dec.17, 2012.

Rails+vertical shaft is chosen for cost and schedule reasons A tunnel to connect them

Engineering design to be started soon.

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Access: two existing Quarries

One for vertical shaft One for rails

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Experimental hall

Preliminary study shows that: Stability of the hall is not a problem Total time needed for construction is 3 years

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Cost estimate

Unit price ($) quantity Cost (M$) R&D 10

Civil & utilities 70 Central Detector 30

PMT 3000 20000 60 HV, electronics,trigger,DAQ, 1000 20000 20

LS & equipment 3000 20000 t 60 VETO 10

Assembly & installation 10 Contingency 30

total 300

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Project Status A lot of progress since summer: much fast than what

we anticipated Great support from CAS: “special fund for advancement” We passed a number of reviews:

Sep. 28 Oct. 9 Dec. 18 Jan. 7. (equivalent to CD1):

– Funding for R&D – Funding for civil preparation: geological survey, engineering

design,…

No final words yet, but we believe there should be no problems

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Overall Schedule Complete conceptual design, complete civil design, & bidding

Start civil construction, complete prototyping (PMT & detector)

PMT production line manufacturing

Start PMT production, start detector production or bidding

Complete civil construction, start detector construction & assembly

Start LS production

Complete detector assembly & installation, & LS filling

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Kaiping: a tourist site with no industry Famous for its architecture: mixture of east & west

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Summary “Daya Bay II” is a project with a very rich and interesting physics

program Although challenging, initial study shows that it is not impossible A few R&D efforts already started, more will come Detector design and civil design has been started Good support from the local government & the Chinese funding

agencies Need more collaborators, more support from the community and

funding agencies

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Welcome to join us, mail to: liwd@ihep.ac.cn, Thanks

Backup

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More photons, how?

Highly transparent LS: Attenuation length/D: 15m/16m 30m/34m ×0.9

High light yield LS: KamLAND: 1.5g/l PPO 5g/l PPO Light Yield: 30% 45%; × 1.5

Photocathode coverage : KamLAND: 34% ~ 80% × 2.3

High QE “PMT”： 20” SBA PMT QE: 25% 35% × 1.4 or New PMT QE： 25% 40% × 1.6 Both： 25% 50% × 2.0

4.3 – 5.0 (3.0 – 2.5)% /√E

Other contributions： 0.5% constant term & 0.5% neutron recoil uncertainty 29

Precision measurement of mixing parameters

Fundamental to the Standard Model and beyond Probing the unitarity of UPMNS to ~1% level !

Uncertainty from other oscillation parameters and systematic errors, mainly energy scale, are included

Current Daya Bay II

∆m212 3% 0.6%

∆m223 5% 0.6%

sin2θ12 6% 0.7% sin2θ23 20% N/A sin2θ13 14% 4% ~ 15%

Will be more precise than CKM matrix elements ! 30

Option 1: no steel tank No more interference “Easy” for PMT holding Water buffer, No MO cheap Difficulties:

Larger pressure difference: 15% density difference leads to a maximum pressure of ~6m in air Stress calculation shows that it is a 5cm thick acrylic is feasible but in really…

A normal aquarium Not a major problem, but takes too long time for construction? However, SS frame is quick for PMT installation

Inner layer(Acrylic)：~Φ34.5m Outer layer (SS frame)：~Φ37.5m

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Option 2: Acrylic box Mineral Oil in the optical modules. pipe for filling MO and cabling Concerns

Leakage through cables

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connect to other modules

MO

MO

LS Acrylic box

MO

LS

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Event Type Raw rate Reduction Radioactivity ~5Hz (PMTs)

~5Hz (LS) Use low radioactivity PMTs; LS purification

Cosmogenic isotopes (delayed)

~550/day ~320/day (tighter delayed energy cut, e.g, 2.0MeV< Ed<2.45MeV)

Spallation neutron

~1.6Hz 7/day (2ms muon veto)

Accidentals ~1000/day ~4/day (prompt-delayed distance Rp-d < 2m) ~2/day (tighter delayed energy cut, e.g, 2.0MeV< Ed<2.45MeV)

Fast neutron ~0.15/day 9Li/8He ~122/day ~60/day (2s Shower muon veto)

~0.3/day (distance to muon track Rd2µ < 5m and 2s veto, will lead to 8.4% dead volume)

Estimated anti-neutrino signal rate: ~40/day