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Measuring the Low Energy Solar Neutrino Spectrum LENS-Sol SNOLAB Workshop, Sudbury, Aug 15, 2005

Measuring the Low Energy Solar Neutrino Spectrum LENS-Sol SNOLAB Workshop, Sudbury, Aug 15, 2005 R. S. Raghavan Virginia Tech. LENS-Sol / LENS-Cal Collaboration (US-Russia) (2004---) Russia: Institute of Nuclear Research (INR Mosow)

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Measuring the Low Energy Solar Neutrino Spectrum LENS-Sol SNOLAB Workshop, Sudbury, Aug 15, 2005

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  1. Measuring the Low Energy Solar Neutrino Spectrum LENS-Sol SNOLAB Workshop, Sudbury, Aug 15, 2005 R. S. Raghavan Virginia Tech

  2. LENS-Sol / LENS-Cal Collaboration (US-Russia) (2004---) Russia: Institute of Nuclear Research (INR Mosow) I. Barabanov, L. Bezrukov, V. Gurentsov, V. Kornoukhov, E. Yanovich INR (Troitsk) V. Gavrin et al; A. Kopylov et al U. S. BNL A.Garnov, R. L. Hahn, M. Yeh ORNL J. Blackmon, C. Rascoe, A. Galindo-Urribari Princeton: J. Benziger U. North Carolina A.Champagne V. T. Z. Chang, C. Grieb, M. Pitt, RSR, R.B. Vogelaar R.S.Raghavan/VT/June05

  3. LENS-Sol GOAL: Experimental Measurement of the Neutrino Luminosity of the Sun (3-4%)  Measure the low energy neutrino spectrum (pp, Be, …) in real time & with precision  Exptal Tool: Tagged CC Nu Capture in Indium νe + 115In  e- + (delay) 2 γ + 115Sn solar signal tag

  4. LENS-Sol-- Low Energy Solar Nu Spectroscopy via Indium --Basics • CC Nu Capture in 115In to • excited isomer in 115Sn • Tag: Delayed emission of 2 γ’s • Threshold: 114 keV  pp Nu • 115In abundance: ~96% • Basic Bgd Challenge: • Natural β-radioactivity of In • In β-Spectrum overlaps pp • signal (Be, CNO not affected • βmax energy = tag energy R.S.Raghavan/VT/June05

  5. Expected Result: LENS-SolSignal= [SSM(low CNO)+LMA] x Detection Efficiency: pp ~40%; Be 85%; pep 90% Rate: pp 25 /y /t In For pp ± 3%, need 2000 ev. / 5y ~10 keV det . threshold Detector Resolution Included (800 pe/MeV) pp 7Be pep CNO Signal Electron Energy (MeV) Nu- capture Signature: Isomeric Coincidence decay with τ =4.76 µs Bgd measured concurrently with signal 2000 pp events (0-10 µs) generated: Fit S=2044±62; (3.1%) S/N=1 (in 0-10µs) Fit S=2031±51; ( 2.5%) S/N=3 S/N=1 S/N~1 Adequate For Precision Flux Random coinc bgd S/N=3 signal

  6. NEW SCIENCE—Discovery Potential of LENS Solar Nu spectrum <5 MeV Yet UNOBSERVED after 40 y of solar nu’s !!! APS Nu Study 2004Lo Energy Solar Nu Spectrum: one of 3 Priorities • In First two years of Data (No source Calib needed) • Proof of MSW LMA Physics from Pee of pp & Be nu • --No proof yet! (no d/n effect, spectral shape a problem?) • Non-standard Fundamental Interactions? • CPT Invariance of nus ? • RSFP/ Nu magnetic moments—Time dependence? • In Five Years (with source Calib): pp Be fluxes measured to 3% • First Exptaltest of Neutrino Luminosity Photon Luminosity • Ultimate test of • Neutrino Physics and Solar Astrophysics • Neutrino Physics: Precision Measurement of θ12θ13 • Sterile Neutrinos? • Astrophysics: Is the Sun getting Hotter? • Hidden new source of energy of Sun? R.S.Raghavan/VT/June05

  7. LENS: Studied world wide since 1976 ! - Dramatic Progress in 2005- 2004  2005 or Cube lattice or non-hybrid longitudinal modular design Longitudinal modules + hybrid design • In: 30 ton for 1900 pp’s /5y • Total mass LS: 6000 ton • PMTs: ~200,000 • In: ~14 ton for 1970 pp’s /5y • Total mass In LS : ~175 ton • PMTs: ~6,500 ( MPIK Talk at DPG 03/2004)

  8. LENS Progress- - How?-- 2004  2005 • Major Advances in Scintillator Chemistry • Absorption length ~ 1.5m @ 5% In > 10m @ 8% In • Module size: ~ 1.5m ~ 6m • Photoelectron yield:~ 230 pe/MeV ~ 900 pe/MeV • + high energy resolution: • Structure of internal 115In Bgd: • partial study (1 component) complete study (5-6 comps.) • only single- decay with BS multi- decays with or w/o BS • considered 498keV  from decay to 115Sn* (single- decay not dominant!) • New Insights in Analysis Strategy • Old: pp-efficiency: ~ 20% New: ~ 45% • Signal/Noise: ~ 1 ~ 3 • NewDetector design: • Design: Hybrid Hybrid design obsolete • Longitudinal modules - Cube lattice - • Event location analog- via PMT timing Event location digital

  9. Components of Indium radioactive bgd In115 0-300(e1) β1 (Emax< 2 keV) (1.2x10-6)* 116 (g2) β0 , γ0 (BS) (Emax = 498 keV) BGD 498 keV 498(g3) Sn115 In tag search volume around vertex of initial beta, occurrence of a random event with minimum Nhit =3 1 beta decay: A1 = beta + BS gamma (Etot = 498 keV) A2 = 498 gamma 2 beta decays in random coinc: B = beta, BS or 498 in any combination from each beta decay 3 beta decaysin random coinc : C = 3 betas mostly 4 beta decays in random coinc: D * Cattadori et al (2003) Sn SIGNAL In * Cattadori et al: 2003 Only A1 considered up to 2004 ! R.S.Raghavan/VT/June05

  10. Signal /ton In/y In Bgd /ton In/y A1 A2 B RAW 62.5 (singles) 75x1011 (Singles) Vertex Del.Coinc. (Granularity: 35g/ton) 62.5 2.8x105 8.5x104 3.3x103 1.9x105 + Min 3 Hits 58 3x104 2.6x104 3x103 1.4x103 +Tag Energy 53.5 3x102 2 6 290 +Tag topology 32 10.6 1.6 5 4 Task of Design and Analysis is to suppress bgd by only 3x105--- NOT ~1011  Generate 4x106 events for analysis Bgd Suppressed by a factor ~1011 Signal Loss Factor ~2 Role of Experimental Tools in Bgd Suppression in LENS-Sol

  11. Basic Design Vectors • Detection Technology: • In loaded liq. Scintillator (InLS) (E resln) • Advances in Scint. Chemistry • DetectorArchitecture: • Segmented /Granularity ~1kg/100 ton • New Design • Bgd Suppression at high Det. Efficiency • New Analysis Strategy

  12. In LS Status (July ‘05) – Summary 1 Indium conc. ~8 wt% (higher may be viable) 2.Scintillation signal eff (typical): 9000 hν/MeV 3.Transparency at 430 nm: L(1/e) (typical): 10 m 4.Chemical and Optical Stabililty: ~ 2 years 5. InLS Chemistry Robust (>1000 syntheses ) BC505 Std 12000 hν/MeV InLS (PC:PBD/MSB): 10800 hν / MeV In 8%-photo Light Yield from Compton edges of 137Cs γ-ray Spectra ZVT27; Abs/10cm=0.004; L(1/e)=10.8 m ZVT28,32: Abs/10cm=0.002; L(1/e)~20m • Milestones unprecedented in metal LS technology • LS technique relevant to wide science experiments • Basic Bell Labs patent • Applied 2001; awarded: 2004 PC NEAT R.S.Raghavan/VT/Aug 05

  13. Detector Design:---Segmented • Objective: Moderate Granularity (~1kg/100 T) • Two Approaches for close packed architecture: • Longitudinal Modules (1-D) (“classical”) • Scintillation Lattice “chamber” (3-D) (new) • Both Designs under study • Scintillation Lattice Design Details • in this talk R.S.Raghavan/VT/June05

  14. NEW DETECTOR CONCEPT—SCINTILLATION LATTICE (RSR ’93) GEANT Simulation: ideal optics Concept • Light output 75% (6PMT) vs 50% (2PMT) in long. modules • Precise 3D DigitalEvent Localization • ~10cm v. 60 cm (±2σ) in longitudinal modules • Event localization independent of event energy • Particle tracks, γ-ray shower structure directly seen • reconstructed hit times  reduced randoms

  15. Perfect optical surfaces Ideal optics: 20 pe rough optical surfaces: 20% of light with non-ideal optics: 12 pe in vertex + 4pe in “halo” Vertex definition in non-smooth optical channels 12.5 cm cells in 4x4x4m cube 100 keV event /9000 hν/MeV Total signal 6x16=96 pe

  16. 5x5x5m Cube 18cm cells—1100 pe/MeV 12.5cm cells 950 pe/MeV 7.5cm cells 700 pe/MeV

  17. Analysis • Basic Constraining Tools: • (key for (A1, A2) • Total Shower Energy of tag candidate • (g2 energy in vertex wide open) • 2. No. of hits in tag candidate shower • (key for B, C, D…) • 3. Shower sphere radius • 4. Maximum inter-hit distance • 5. e1-g2 coincidence window 10µs R.S.Raghavan/VT/June05

  18. Before Cuts After Cuts Bgd Nu Bgd Nu BS >450 kev • Surviving bgd different for • different Nhit showers • New Analysis Paradigm (VT) • Apply progressively less tight cuts for larger Nhit Increased detection Efficiency and lower bgd g2+g3 nu events 498 Total Tag Energy R.S.Raghavan/VT/June05

  19. Analysis Strategies: Basic selection: Events with given Nhit Every hit in candidate event is a possible vertex with a previous beta in that cell to mimic nu event NEW ANALYSIS STRATEGY Classify events according to NHit Optimize cut conditions separately for each class R.S.Raghavan/VT/June05

  20. Typical LENS-Sol: DESIGN FIGS. OF MERIT (Lattice Design) 4mx4mx4m supermodules:InLS: 8% In; L(1/e) =1000cm; Y= 9000hν/MeV; Cell Size (mm x mm x mm) Det Eff % Nu Rate /T In/y Bgd Rate /T In/y S/N Mass for 2000 ev/5y (pp flux3%) T (In) g2 T (InLS) 75 1000pe/MeV4x4x4 64 40 13 3 10 125 g2+g3 125 950pe/MeV 5x5x5 41.8 26 9 2.9 15.3 190 Shower Rad. 180 1000 p/MeV 6x6x6 33.1 20.7 22 1 19.3 240 R.S.Raghavan/VT/June05 R.S.Raghavan/VT/June05

  21. Summary • Major breakthroughs in • In LS technoloy • Detector Design • Analysis and Background Simulations • Conceptual feasibility of In-based LENS secure • Simple Small ( < 10 t In /125 ton InLS) LENS in view • Next Steps—Work in Progress • Chemical Technology of large scale InLS production • Detector construction technology R.S.Raghavan/VT/June05

  22. VT-NRL Low Bgd Laboratory @ Kimballton Mine VA

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