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Low Energy Neutrinos Neutrino Luminosity of the Sun & LENS Neutrino Oscillation Workshop

Low Energy Neutrinos Neutrino Luminosity of the Sun & LENS Neutrino Oscillation Workshop Conca Specchiulla, September 11, 2006 Christian Grieb Virginia Tech. LENS Expected Result: Low Energy Solar - Spectrum. >98% Flux <2MeV. Signal ( t = 4.76 µs). LENS-Sol Signal =

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Low Energy Neutrinos Neutrino Luminosity of the Sun & LENS Neutrino Oscillation Workshop

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  1. Low Energy Neutrinos Neutrino Luminosity of the Sun & LENS Neutrino Oscillation Workshop Conca Specchiulla,September 11, 2006 Christian Grieb Virginia Tech

  2. LENS Expected Result: Low Energy Solar -Spectrum >98% Flux <2MeV Signal (t = 4.76 µs) • LENS-Sol Signal • = • SSM(low CNO) + LMA • x • Detection Efficiency e • Rate: pp 40 pp ev. /y /t In • 2000 pp ev./ 5y/10t In  ±2.5% • Design Specification: S/N ≥ 3 pp:e = 64% 7Be:e = 85% pep:e = 90% Access to pp  spectral shapefor the first time

  3. Test of Solar Models Solar Neutrino fluxes at the earth according to SSM Solar models predict relative intensities in the pp-chain Reaction rates depend on temperature profile and abundances Cross check with measured fluxes (using neutrino oscillation physics) Data taken from John N. Bahcall, M.H. Pinsonneault, Phys.Rev.Lett.92, 121301 (2004)

  4. Neutrino Inferred Solar Luminosity Nuclear reactions in the pp-chain: Nuclear fusion reactions in the solar core pp-chain + CNO cycle H.A. Bethe Phys.Rev.55, 434 (1939) No solar model needed J. N. Bahcall and R. Ulrich, Rev. Mod. Phys.60, No. 2, p. 297 (1988)

  5. ? = Solar Luminosity: Neutrino vs. photon Energy Balance: Measured neutrino fluxes at earth + oscillation physics nuclear reaction rates energy release in the sun Solar luminosity as measured by photon flux • Will be met under these conditions: • Fusion reactions are the sole source of energy production in the sun • The sun is in a quasi-steady state (change in 40,000 years is negligible) • The neutrino oscillation model is correct & no other physics involved; • From a single detector: • Test of astrophysics, solar model (absolute fluxes); • Test of neutrino physics (LMA-MSW at low E, NSI, mass-varying ns, CPT invariance, Q13, …) (relative fluxes)

  6. Neutrino inferred Luminosity of the Sun - Experimental Status Predicted relative neutrino fluxes at the sun (SSM): Main contributions: pp 0.91 7Be 0.074 (CNO 0.014) 8B 0.00009 Measured neutrino fluxes at the earth: 8B (SK, SNO) known very well 7Be + 8B (Cl) sensitive mostly to 8B pp + 7Be + 8B (Ga) 7Be (Borexino, Kamland – in the future) • in principle can deduce pp- flux Problem: disentangling fluxes from individual neutrino sources R.G.H.Robertson, Prog. Part. Nucl. Phys. 57, 90 (2006) J.N.Bahcall and C.Peña-Garay, JHEP 0311, 4 (2003) Experimental status – No useful constraint!

  7. J. N. Bahcall and R. Ulrich, Rev. Mod. Phys.60, No. 2, p. 297 (1988) J. N. Bahcall and R. Ulrich, Rev. Mod. Phys.60, No. 2, p. 297 (1988) Temperature in the Solar Core impacts Neutrino Spectra, not just relative fluxes Temperature Profile Neutrino Production

  8. Temperature in the Solar Core impacts Neutrino Energies, not just relative fluxes pp- and pep neutrino production temperature and related Gamow peak energy: Relative kinetic particle energies add to the Q-value of capture and fusion reactions. Not all energies contribute evenly: pep pp-fusion: Gamow Peak at pp endpoint shifted up by ~5.2keV E0 pp Maxwellianenergydistribution X Tunnelingprobability C. Grieb and R.S. Raghavan, hep-ph/0609030 (2006) 7Be electron capture: maxwellian energy distribution shifts mean energy of 7Be n line by <E> ~ 1.29 keV J.N. Bahcall, Phys. Rev. D49(8), 3923 (1994) J.N. Bahcall, Phys. Rev. D44(6), 1644(1991) pep: combination, delta D<E> ~ 6.6 keV hep: J.N. Bahcall, Phys. Rev. D44(6), 1644(1991)

  9. Measurement of the Gamow Energy of pp-fusion in the sun with (improved) LENS Top:pp- spectrum with/without Gamow shift Bottom: Signal spectrum in LENS with/without Gamow shift 12t Indium - 6years - dE/E=6% at 300keV Measured Gamow shift in improved LENS: 10000 simulations with ~3000 pp n events each s=1.62keV Conclusion: Slightly improved LENS can detect the predicted Gamow shift in the pp- endpoint DE=5.2keV with 95% confidence. C. Grieb and R.S. Raghavan, hep-ph/0609030 (2006)

  10. LENS-Indium: Foundations CC -capture in 115In to excited isomeric level in 115Sn Tag: Delayed emission of (e/)+  Threshold: 114 keV  pp-’s 115In abundance: ~ 96% • Background Challenge: • Indium-target is • radioactive! (t = 6x1014 y) • 115In β-spectrum overlaps • pp-signal • Basic background discriminator: • Time/space coincidence tag • Tag energy: E-tag = Eβmax+116 keV • Requires good spacial resolution • 7Be, CNO & LENS-Cal signals • not affected by Indium-Bgd!

  11. BC505 Std 12000 h/MeV 8% InLS (PC:PBD/MSB) 10800 hν / MeV In 8%-photo Light Yield from Compton edges of 137Cs -ray Spectra L(1/e)(InLS 8%) ~ L(PC Neat) ! ZVT39: Abs/10cm ~0.001;  L(1/e)(nominally) >>20 m Norm. Absorbance in 10 cm InLS PC Neat l (nm) Indium Liquid Scintillator Status Milestones unprecedented in metal LS technology LS technique relevant to many other applications 1. Indium concentration ~8%wt (higher may be viable) 2. Scintillation signal efficiency (working value): 9000h/MeV 3. Transparency at 430 nm: L(1/e) (working value): 10m 4. Chemical and Optical Stability: at least 1 year 5. InLS Chemistry - Robust Basic Bell Labs Patent, filed 2001, awarded 2004

  12. New Detector Technology - The Scintillation Lattice Chamber Test of double foil mirror in liq. @~2bar Light propagation in GEANT4 Concept 3D Digital Localizabilityof Hit within one cube  ~75mm precision vs. 600 mm (±2σ) by TOF in longitudinal modules  x8 less vertex vol.  x8 less random coinc.  Big effect on Background  Hit localizability independent of event energy

  13. Indium --Background Topology – Space / Time coincidence β1 (Emax< 2 keV) (b = 1.2x10-6)* E() -114 keV 115In =4.76s 115In e/ 116 keV β0 + n (BS) (Emax = 499 keV)  498 keV  498 keV 115Sn 115Sn *Cattadori et al: 2003 Background Signal Signal Signature: Prompt e- ( ) followed by low energy (e-/) ( ) and Compton-scattered  ( ) Background: Random time and space coincidence between two -decays ( ); Extended shower ( ) can be created by: a) 498 keV  from decay to excited state; b) Bremsstrahlungs -rays created by ; c) Random coincidence (~10 ns) of more -decays; Or any combination of a), b) and c).

  14. Indium --Background Discrimination • Background rejection steps: • Time/space coincidence in the same cell required • for trigger; • B. Tag requires at least three ‘hits’; • C. Narrow energy cut; • D. A tag topology: multi- vs. Compton shower; • Classification of events according to hit multiplicity; • Cut parameters optimized for each event class • improved efficiency; Reduction by ~3.107 through time/space coincidence

  15. Summary Major breakthroughs in LENS: • ●Indium liquid scintillator synthesis • ● New detector technology (Scintillation Lattice Chamber) • ● GEANT4 Simulation of Indium -background • Basic feasibility of In-LENS-Sol secure (10t In, 125t In-LS) Science in LENS: • Measure solar -spectrum below 2MeV •  Luminosity of the sun • Gamow shift of pp- spectrum probes the T profile • Test of Astrophysics &  physics in one experiment Next Step: Test all the concepts and the technology developed so far & demonstrate Indium solar signal detection: MINI-LENS - 130 liter InLS scintillation lattice detector

  16. LENS-Sol / LENS-Cal Collaboration (Russia-US: 2004-) Russia: INR (Moscow): I. Barabanov, L. Bezrukov, V. Gurentsov, V. Kornoukhov, E. Yanovich; INR (Troitsk): V. Gavrin et al., A. Kopylov et al.; U. S.: BNL: R. L. Hahn, M. Yeh; U. N. Carolina: A. Champagne; ORNL: J. Blackmon, C. Rascoe, A. Galindo-Uribarri, Q. Zeng; Princeton U. : J. Benziger; Virginia Tech: Z. Chang, C. Grieb, M. Pitt, R.S. Raghavan, D. Rountree, R.B. Vogelaar; New collaborators cordially invited!

  17. Additional Slides

  18. Signal Reconstruction • Event localization relies on PMT hit pattern (NOT on signal timing) • Algorithm finds best solution for event pattern to match PMT signal pattern • System is overdetermined, hardly affected by unchannelled light • Timing information + position  shower structure

  19. Indium Background Simulations and Analysis • Data: Main Simulation of Indium Events with GEANT4 • ~ 4x106 In decays in one cell centered in ~3m3 volume (2-3 days PC time) • Analysis trials with choice of pe/MeV and cut parameters (5’ /trial) • Analysis Strategy • Primary selection - tag candidate shower • events with Nhit ≥ 3 • Classify all eligible events (Nhit ≥ 3) • according to Nhit • Optimize cut conditions individually for • each Nhit class • Main Cuts • Total energy: g2+g3 • Tag topology: Distance of lone  from • shower

  20. MINILENS Final Test detector for LENS LS Envelope • InLS : 128 L • PC Envelope : 200 L • 12.5cm pmt’s : 108 InLS InLS 500 mm 500 mm Opt segmentation cage Passive Passive Mirror Mirror 5 5 ” ” PMT PMT Shield Shield

  21. MINILENS: Global test of LENS R&D • Test detector technology • Large Scale InLS • Design and construction • Test background suppression of In • radiations by 10-11 • Demonstrate In solar signal detection • in the presence of high background • Direct blue print for full scale LENS

  22. Proxy pp- events in MINILENS • Proxy pp nu events in MINILENS from cosmogenic 115In(p,n)115Sn isomers • Pretagged via , p tracks • Post tagged via n and • 230 s delay •  Gold plated 100 keV • events (proxy pp), • Tagged by same cascade • as In- events •  Demonstrate In- Signal • detection even in • MINILENS

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