Neutrino Working GroupKevin T. Lesko

12 Neutrino Mixing

Next Generation

Solar Neutrino Experiments

National Underground Scientific Laboratory

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Where are we with Neutrinos after SNO

& KamLAND-I?

– Reduced e MSW space by 7 orders of magnitude– No dark side e (tan2<1)– Most likely LMA (confirmed by KamLAND! assuming CPT)– Support of MSW affects– Massive neutrinos (small m2)– Large mixing angles

– m ≤0.7 eV: WMAP

After WMAP?

Neutrino Mixing Parameter 12

• SNO + KamLAND– Now

20

15

10

5

0

reactor neutrinos geo neutrinos background

25

20

15

10

5

086420

Prompt Energy (MeV)

2.6 MeVanalysis threshold

KamLAND data no oscillation best-fit oscillation

sin22=1.0m2=6.9 10x -5eV2

• SNO + KamLAND–Next year (guess)

KamLAND II (7Be)

Low Energy pp Experiment

Flux measurement limited to 7 -10%

Flux measurement down to 1-3%

How can we do better? How much better can we do?

Neutrino Mixing Parameter 12

• Fundamental neutrino parameter, neutrino properties– The angles are large and at least 12 is non-maximal– Is the MNS matrix unitary?

• Input to CP violation experiment analysis

• Synergisms with other fundamental measurements

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P(ν μ → ν e ) − P(ν μ → ν e ) = −16sinθ12 cosθ12 sinθ13 cos2 θ13 sinθ23 cosθ23

sin(Δm12

2

4 EL)sin(

Δm132

4EL)sin(

Δm232

4EL)

Physics using the sun: 7Be and pp neutrinos

• Oscillation Parameter 12

7Be - confirm 12 from SNO with ~7 to 10%pp yields factor 2-3 improvement in 12 ~1 to 3%unitarity of the MNS mixing matrixmixing angles are large but not maximal-why?input into ultimate CP studies

• Sterile Neutrinoscurrently SNO yields ~30% limitsolar neutrinos absolute intensity good ~ 1%

• Magnetic Momentslooking down to ~50 keV ~ 10-11 B

d/dy• Solar Physics

SSM - pp flux, 7Be fluxCNO - ~1.2 to 1.7 MeV, 50% uncertaintyCNO~0.1 to 0.2 x 7Be and 20x 8B

Surprises to Conventional Wisdom

7Be upgrade to KamLAND

Dominant backgrounds:• 85Kr• 210Pb• 210Bi (from Rn)

Upgrade a coincidence experiment to a singles, low energy experiment: Backgrounds will be a dominate concern.

Backgrounds:Spallation,Long-lived radioactivity

Adding solar signals

7Be window

Requirements for reactor e detection

238U 232Th ~ 10-14 g/g40K ~ 10-15 g/g

7Be

Top of the chains look encouraging,But radon is leaking in, lots of Kr

7Be Neutrino Experiment at KamLAND

U, Th chains look pretty good, wrt supported chains

Radon and 85Kr require ~ 1:106 reduction

210Pb needs large reduction in the bulk liquid Scintillator

Collaboration (US and Japanese) now gearing up to address these issues. Japan has received some funding already (site improvements and some purification upgrades). US proposal for a KamLAND upgrade is now being considered by the US collaboration. Proposal might include items such as improved purification techniques, fixing lots of piping leaks, fresh air ducting, cave linings, etc.

Next Generation Solar Neutrino Experiment: pp

• Long Term R&D Investment– Not a quick & dirty experiment

• R&D applicable to several experimental fronts– Low energy solar neutrino experiments– Double beta decay– Other experiments

• Experiments are challenging• For ultimate physics requires both CC and NC

measurements• Requires NUSEL; a deep site

Issues for Low Energy Solar Neutrino Experiment

BackgroundsInternalExternal

Detector PerformanceDetector EfficiencyDetector ResolutionRobust SignalStability

Environmental Considerations

Count Rate

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Neutrino Elastic Scattering

e + e - => e + e –

• Measure RATE & RECOIL SPECTRA of pp ( 7Be, CNO)≤ 50 keV Threshold

•e Cross Sections Accurately Known.

• High Statistics for Moderate Detector Mass ( > 90 % of (solar) ; 3000 – 6000 events per 10 tonne-yr )

• (pp) Theoretical Prediction (SSM) ~ ±1%

(more precisely predicted than reactors

~2% Bugey potential Standard Candle)• Not affected by power companies or Atomic

Energy Commission reporting of Power

Levels

Preliminary Design of a Low Energy Solar Neutrino Detector

Kajiyama Lanou LeskoPoonSeidel

LBNLBrown U.

SpaceInfrastructureConstructionSafety

Low Energy Solar Neutrino Experiment LDRD

Why Superfluid Helium?• High Rate ES (~ 2 events/tonne/day detected)• Intrinsically pure• Potentially good signal/bckgrd discrimination• Significant R&D invested already

• scintillation yields, Rayleigh scattering, redundant signals, signal processing, background discrimination, etc.

Why Berkeley Lab?• Backgrounds (shielding & induced), Calibration and Calculations• Detector Development, signal processing (scintillation light) • Detector Design & Construction• Connections to UCB Physics• History with Neutrinos• Excellent Connection to LRP & NUSL

PlanBackgroundsDevelop Detection TechniquesDevelop Prototype

Participation of Berkeley Lab in NUSELScience DrivenPositions Berkeley Lab with LRP priorityMajor Roles in New Laboratory• Science Experiments

– Low Energy Solar Neutrino Experiment R&D• Monte Carlo Simulations & Backgrounds• Detector R&D• Prototype Detectors

• Ultralow Background Counting Facility• Monte Carlo Simulations• Detector Designs• Engineering Design and Conceptual Design

• Earth Sciences Division• Nuclear Astrophysics - under discussion • Double Beta Decay - under active discussion

Why should LBL Participate in NUSEL?

• Connections to existing experiments, upgrades, and future experiments.

SNOKamLANDAstrophysicsDouble Beta Decay

Cuore & Majorana

• Low Background Counting• Engineering, Design, Management • Major Priority for Nuclear Physics Community• Long baseline experiments, CP violation, proton

decay in the future.

What is the status of NUSEL? What is Berkeley’s role in NUSEL?

• Workshops 2000-2002• Long Range Planning Process

(NSAC, SNOWMASS)• National Priority• NSF Proposal submitted

• Panel and Paper Reviews• NeSS Workshop• Awaiting NSF Board Action• NSF Proposal being refined

• Defining LBL Role in Proposal

• Still no action from NSF• Homestake not flooded• Proposal being refined and

improved• NSF Management urges

patience

• Recently:OSTP discussing Major Initiative in Particle/Astrophysics highlighting NUSEL

Lesko: NUSEL Executive CommitteePoon, Heeger: members of working groups

NUSEL - recent news

• Barrick just (10 April) announced plans to flood the Homestake mine beginning on 14 April. A major set back for Homestake proposal from the University of Washington. - Could just be posturing by Barrick to obtain operating expenses or attention.- If real it would open the door to consideration of the full range of siting options: San Jacinto, Nevada, Henderson mine, Eastern California, etc.

• OSTP considering a major initiative in Astro-particle physics, NUSEL is a major focus of this initiative.

Summary12

Low Energy Solar Neutrino ExptNational Underground Laboratory

• Multiple excellent science objectives • Long term mission• Synergism with other fields and physics

• Capitalizes on lab expertise and experience• Positions lab with community priorities

Status of HERON: Substantial R&D already done with prototypes: Absolute measure of scintillation yield: >30,000 photons/MeV; Rayleigh scattering

Demonstrated two-channel detection of low energy ’s & ’s: photons & phonons

Developed calorimeter wafers magnetic readout. 6 eV FWHM on 6 keV x-ray

Full simulation of coded aperture on backgnd & signal photons.

current version 3x10-3 backgnd reject; almost good enough for no electroforming In progress:

• New prototype & expts. on scintillation & drifted charge ( “e-bubbles”).

• Experiments for single 16eV photon sensitivity on larger calorimeters.

• Testing different versions of coded aperture in full simulation.

• Decision on constructing sizeable prototype (1-1.5 yr.?)

When could there be a full HERON?: a) When & where will there be an underground lab? b) Fabricate & construct underground. c) Infrastructure for doing so? d) 2-3 yrs. From a) & c). e) Cost: $30-40 M (FY2001 $) detector, shields & aux. equip.

Low Energy Neutrino Experiment Challenges

Requires VERY LOW THRESHOLD

< 50 keV FORMIDABLE BACKGROUNDS

target, container, environment, muon spallation SIGNAL: SINGLE ELECTRON RECOIL NEEDS PRECISION

high statistics, need to pin systematics on FV, dE/E, etc.

)e= 1/6

“appearance” but lower sensitivity to NC COMPLEMENTARY CC EXPTS VERY LARGE

low event rate/ton; cross-sections less well known

How does HERON address these challenges? A cryogenic scintillation-”plus” detector.

Use Superfluid helium as target superfluid free of any other substance

Helium is strong scintillator at 16 eV. >30,000 photons/MeV; (Rayleigh) > 200 m

Redundant detection channels. Scintillation, Phonons & “e-bubble”.

No PMT’s. Scintillation, phonons, electron all detected on same sapphire wafer

calorimeters, looking into additional detection devices

Depth >4500 mwe and immunity of Helium to muon spallation/ capture

External shield from hall rock activity,

BUT: Helium not good self-shield from any activity in container:

* Capitalize on different signature of background. s Multiple Comptons

* Good measurement of event positions & topology.

utilize coded aperture wafer array point vs. distributed source

* Possible electroforming of interior cryostat.

Preliminary Design of a Low Energy Solar Neutrino DetectorSuperfluid Helium (HERON) type detector

Kajiyama Lanou LeskoPoonSeidel

MassBackgroundsShieldingConstruction

Log-Likelihood Coded Aperture

• 20 tonnes total Helium.• Variable fiducial.

SNO+Cl +Ga Standard SNO+Cl+Ga (5%+ 2% theory)

SNO+Cl+Ga (1%+2% theory)

From Aspen 2002

Barger 0204253 Log(tan2)

Log(tan2)

Log

(m

2 )L

og(

m2 )

Where will we be in 3-5 years?Neutrino Oscillations - fundamental issues

• LMA, m2 < 1 x 10-4 ev2 KamLAND can observe oscillation signature, if m2 > 1 x 10-4 ev2 need new experiments

– Low masses Need better 12 => SNO, Low E Solar, KamLAND II– High Masses, still need oscillation signature and need better 12

=> HLMA experiments for m2 SNO, Low E Solar, KamLAND II also will seek oscillation signatures

• LSND confirmed or refuted (miniBOONE) if confirmed => Sterile

– Sterile Neutrinos => BOONE – Sterile Neutrinos => Low E Solar

• (If) Neutrino Oscillations:– Full MNS matrix needs to be filled out - Mixing Parameters => SNO, Low E Solar, KamLAND, LBL, 7Be expts., Minos, miniBOONE, JParc, Off-axis expts, 13 reactor experiments

Neutrino Nature• Majorana or Dirac? (DD, Cuore, Majorana)Mass Scale• Absolute mass scale? (Katrin tritium D, DBD)

–Less likely (harder) after WMAP

SNO NC

20

15

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reactor neutrinos geo neutrinos background

25

20

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086420

Prompt Energy (MeV)

2.6 MeVanalysis threshold

KamLAND data no oscillation best-fit oscillation

sin22=1.0m2=6.9 10x -5eV2