1. Neutrino Working Group Kevin T. Lesko  12 Neutrino Mixing  Next Generation Solar Neutrino Experiments  National Underground Scientific Laboratory

2. Where are we with Neutrinos after SNO & KamLAND-I? – Reduced e MSW space by 7 orders of magnitude – No dark side e (tan 2  <1) – Most likely LMA (confirmed by KamLAND! assuming CPT) – Support of MSW affects – Massive neutrinos (small  m 2 ) – Large mixing angles –  m ≤0.7 eV: WMAP After WMAP?

3. Neutrino Mixing Parameter  12 SNO + KamLAND –Now SNO + KamLAND –Next year (guess)

4. KamLAND II ( 7 Be) 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?

5. 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

6. Physics using the sun: 7 Be and pp neutrinos Oscillation Parameter  12 7 Be - confirm  12 from SNO with ~7 to 10% pp yields factor 2-3 improvement in  12 ~1 to 3% unitarity of the MNS mixing matrix mixing angles are large but not maximal-why? input into ultimate CP studies Sterile Neutrinos currently SNO yields ~30% limit solar neutrinos absolute intensity good ~ 1% Magnetic Moments looking down to ~50 keV ~ 10 -11  B d  /dy Solar Physics SSM - pp flux, 7 Be flux CNO - ~1.2 to 1.7 MeV, 50% uncertainty  CNO ~0.1 to 0.2 x 7 Be and 20x 8 B Surprises to Conventional Wisdom

7. 7 Be upgrade to KamLAND Dominant backgrounds: 85 Kr 210 Pb 210 Bi (from Rn) Upgrade a coincidence experiment to a singles, low energy experiment: Backgrounds will be a dominate concern.

8. Backgrounds: Spallation, Long-lived radioactivity Adding solar signals 7 Be window

9. Requirements for reactor e detection 238 U 232 Th ~ 10 -14 g/g 40 K ~ 10 -15 g/g 7 Be Top of the chains look encouraging, But radon is leaking in, lots of Kr

10. 7 Be Neutrino Experiment at KamLAND U, Th chains look pretty good, wrt supported chains Radon and 85 Kr require ~ 1:10 6 reduction 210 Pb 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.

11. 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

12. Issues for Low Energy Solar Neutrino Experiment Backgrounds Internal External Detector Performance Detector Efficiency Detector Resolution Robust Signal Stability Environmental Considerations Count Rate

13. Neutrino Elastic Scattering  e  + e - => e  + e – Measure RATE & RECOIL SPECTRA of pp ( 7 Be, 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

14. Preliminary Design of a Low Energy Solar Neutrino Detector Kajiyama Lanou Lesko Poon Seidel LBNL Brown U. Space Infrastructure Construction Safety

15. 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 Plan Backgrounds Develop Detection Techniques Develop Prototype

16. Participation of Berkeley Lab in NUSEL Science Driven Positions Berkeley Lab with LRP priority Major 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

17. Why should LBL Participate in NUSEL? Connections to existing experiments, upgrades, and future experiments. SNO KamLAND Astrophysics Double 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.

18. 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 Committee Poon, Heeger: members of working groups

19. 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.

20. Summary  12 Low Energy Solar Neutrino Expt National 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

22. 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.

23. 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

24. 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.

25. Preliminary Design of a Low Energy Solar Neutrino Detector Superfluid Helium (HERON) type detector Kajiyama Lanou Lesko Poon Seidel Mass Backgrounds Shielding Construction

26. Log-Likelihood Coded Aperture

27. 20 tonnes total Helium. Variable fiducial.

28. SNO+Cl +Ga Standard SNO+Cl+Ga (5%+ 2% theory) SNO+Cl+Ga (1%+2% theory) From Aspen 2002 Barger 0204253 Log(tan 2  ) Log(  m 2 )

29. Where will we be in 3-5 years? Neutrino Oscillations - fundamental issues LMA,  m 2 1 x 10 -4 ev 2 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  m 2 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, 7 Be expts., Minos, miniBOONE, JParc, Off-axis expts,  13 reactor experiments Neutrino Nature Majorana or Dirac? (D  D, Cuore, Majorana) Mass Scale Absolute mass scale? (Katrin tritium  D, DBD) –Less likely (harder) after WMAP SNO NC