Panic05

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
gt98 Flux lt2MeV
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 shape for 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)
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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)
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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 (CN
O 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!
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Temperature in the Solar Core impacts Neutrino
Spectra, not just relative fluxes
Temperature Profile

• Neutrino Production

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Temperature in the Solar Core impacts Neutrino
Energies, not just relative fluxes

• Relative kinetic particle energies add to the
  Q-value of capture and fusion reactions.
• Not all energies contribute evenly

pp- and pep neutrino production temperature and
related Gamow peak energy
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
?ltEgt 1.29 keV
J.N. Bahcall, Phys. Rev. D 49(8), 3923 (1994)
J.N. Bahcall, Phys. Rev. D 44(6), 1644(1991)
hep


pep combination, delta DltEgt 6.6 keV
J.N. Bahcall, Phys. Rev. D 44(6), 1644(1991)
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Measurement of the Gamow Energy of pp-fusion in
the sun with (improved) LENS
Toppp-? spectrum with/without Gamow shift
Bottom Signal spectrum in LENS with/without
Gamow shift 12t Indium - 6years - dE/E6 at
300keV
Measured Gamow shift in improved LENS 10000
simulations with 3000 pp n events each s1.62keV
Conclusion Slightly improved LENS can detect the
predicted Gamow shift in the pp-? endpoint
DE5.2keV with 95 confidence.
C. Grieb and R.S. Raghavan, hep-ph/0609030 (2006)
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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 ß-spectrum overlaps
• pp-? signal
• Basic background discriminator
• Time/space coincidence tag
• Tag energy E?-tag Eßmax 116 keV
• Requires good spacial resolution
• 7Be, CNO LENS-Cal signals
• not affected by Indium-Bgd!

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Indium Liquid Scintillator Status
Milestones unprecedented in metal LS
technology LS technique relevant to many other
applications
1. Indium concentration 8wt (higher may
be viable) 2. Scintillation signal efficiency
(working value) 9000 h?/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
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New Detector Technology - The Scintillation
Lattice Chamber
Test of double foil mirror in liq. _at_2bar
Light propagation in GEANT4
Concept

• 3D Digital Localizability of Hit within one cube
• ? 75mm precision vs. 600 mm (2s) by TOF in
  longitudinal modules
• ? x8 less vertex vol. ? x8 less random coinc. ?
  Big effect on Background
• ? Hit localizability independent of event energy

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Indium ?--Background Topology Space / Time
coincidence
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).
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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
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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
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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!
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Additional Slides
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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

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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 g2g3
• Tag topology Distance of lone ? from
• shower

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MINILENS
Final Test detector for LENS
LS Envelope

• InLS 128 L
• PC Envelope 200 L
• 12.5cm pmts 108

InLS
InLS
500 mm
500 mm
Opt segmentation cage
Passive
Passive
5

PMT
Mirror
5

PMT
Mirror
Shield
Shield
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MINILENS Global test of LENS RD

• 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