LENSCAL

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LENS-CAL I. Barabanov, V. Gurentsov, V.
Kornoukhov Institute for Nuclear Research,
Moscow and R. S. Raghavan, Virginia
Tech LONU-LENS Blacksburg, Oct 15, 2006
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Nuclear Matrix Element for Indium Neutrino
Capture Reaction

• The Capture Cross Section is
• s 1.632 x10-44 x gA2 B(GT) We pe F(ZW)
• gA2 1.58
• We Prompt Electron energy in mc2 units
• pe Electron momentum v (We2 1)
• F(Z50, We) Fermi function
• B(GT) is reduced Gamow Teller Nuclear Matrix
  Element
• B(GT) must be calculated/ measured in Laboratory
• Theoretical Estimate made in RSR original PRL
  paper
• Using nuclear systematics and shell model
  parameters of the
• The In (initial) and Sn (final) states
• B(GT) 0.16

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Measurement J. Rapaport et al, Phys.Rev.
Letters 54, 2325 (1985) Performed via
115In(p,n) forward scattering at Indiana U
Cyclotron s (p,n) is proportional to
B(GT) Forward (0o) neutron emission with. Ep 120
MeV and 200 MeV B calibrated against B(F) 3
for Analog state Result B(GT) (neutrino state)
0.17 (10) B(GT) 0 to states upto 4 MeV V.
good agreement with rsr theory
In-Sn neutrino state
Neutrino state
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Neutrino Source Calibration of B(GT)

• In(p,n) reaction is strong interaction reaction
  which measures B(GT) via strong interactions.
• Desirable to have direct weak interaction
  measurement of B(GT)
• Direct measurement using a megCuri neutrino
  source.
• LENS-CAL
• ?Source Technology Expertise developed in
  Russia
• (SAGE detector calibration with 51Cr and 37
  Ar Sources)
• ?LENS-CAL? MegaCurie source made in Russia
• Compact In loaded
  detector
• Operated probably in
  Baksan

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Table I Characteristics of neutrino Sources
for LENS-CAL
Neutrino Energy typically 700 keV
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Source Energy 700 keV OK for LENS-CAL First No
other excited state reached. LENS tag ensures
excitation of specific state in daughter
Sn. Usual problem in radiochem expts such Ga is
not present here Second Energy beyond In
beta Endpoint. So double Coincidence
enough Simplified tag analysis
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• Design Concepts for LENS-Cal Detector
• Indium Density
• Consider a neutrino source in the center of a
  spherical detector
• The event yield Y is
• Y s e ? ? S /(4p r2 ) k 4p r2 dr s e k ?
  R( radius of detector)
• -k the fraction of 4p enclosed by the detector
  array (k 1)
• e the signal detection efficiency ? In foil
  thickness
• Y varies as ? the Indium Density.
• Need design with high Indium density
• In LS typically In is 8 -15
• Can this be increased?
• In foil Plastic Sandwich Stack Detector

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Basic Idea of Sandwich Stack -- Use thin Indium
foil sandwiched by thin plastic bar Thicknesses
Indium foil? Signal electron emerge with high
efficiency Plastic? thickness gt range of
electron Optimized thicknesses In foil 70-100
mg/cm2
Plastic 300 mg/cm2 Good for E? 700 keV
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In Sandwich Stack Expts Bell Labs 1979 Original
Intent pp neutrinos ! ?very thin In foil
lt10mg/cm2 ?plastic 160mg/cm2? ?60g/l Compared
to Ar source In foil 100mg and Plastic 300 mg
??330 g/l Sandwich stack
design offers X2.2 higher Indium density Modules
with Stacks 20x20x200cm Light attenuation
OK Recent INR Monte Carlos Verify
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LENS-CAL Conceptual Design based on Sandwich
Stack In Loading
Side view
Plan view
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60
60
37Ar
37Ar
Ar
37
360
Indium 8 tons Plastic 25 tons.
Indium 100mg/cm2 Plastic 300mg/cm2 Indium
Density ? 0.33 g/cm3. Plastic Module 20x20x200
max Light guides/PMTs
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Preliminary Simulation Results
51Cr source with activity - 5 mCq Neutrino
cross-section capture 3.03x10-44 cm2 In
thickness 0.1 g/cm2 Scintillator slab thickness 3
mm Threshold for neutrino electron 450
keV Threshold of shower energy - 300 keV. Total
In mass 5 t Module cross section
55 cm2 1010 cm2
1515 cm2 Neutrino detection efficiency,
31 26
22 Background (total) per day 1.5
2. 4.4 Number of neutrino
events per 100 d 1515 1271
1075 Good Event Rate and Low intrinsic In
Bgd.
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• New Physics from LENS Cal?
• Look for Sterile Neutrino Oscillations in
  LENS-CAL
• L. Mikaelyan et al, hep-ph/0310246 Jonathan Link
• LSND? ?m2 1eV2 104 x ?m12 2 of reactor ?e
• sin2 2? 0.1to 0.001
• Test at short baselines lt10m available in
  LENS-CAL
• Kamland 105 m x10-4 (0.7/3 MeV) 2m in
  LENS-CAL
• Look for event rate distribution vs. radius in
  LENS-CAL
• 
  detector !

i LSND Collaboration, Phys. Rev.Lett. 79 (1998)
1774 ii KamLand Collaboration, Phys. Rev. Lett.
94 (2005) 081801
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Conclusions Preliminary Analysis Shows Indium
sandwich Stack Detectors with Technically
feasible 51Cr sources are viable Further work
for other sources Source Strengths . Revisit
In LS modules ?lower density but higher
efficiency