Comparing Large Underground Neutrino Detector Technologies: Liquid Argon, Liquid Scintillator, and Water Cherenkov

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Comparing Large Underground Neutrino Detector
TechnologiesLiquid Argon, Liquid Scintillator,
and Water Cherenkov

• John G. Learned
• University of Hawaii
• at ANT09, Hawaii

A personal view, based upon experience with all
three technologies.
Good source papers Report on the Depth
Requirements for a Massive Detector
at Homestake, arXiv0907.4183v2 Large
underground, liquid based detectors for
astro-particle physics in Europe scientific
case and prospects, arXiv0705.0116v2
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The three detectors in the LAGUNA study
1 vertical
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Material Properties
Property Scint Water Argon
Z 1,12 (11) 1,16(21) 40
X0 /cm 42 36 20
p /gm/cm3 0.8 1.0 1.0 1.39
?int /gm/cm2 75.7 84.6 117.2
?col /gm/cm2 55.7 60.1 76.4
-dE/dx /gm/cm2 2.30 1.99 1.52
n (optical) 1.49 1.33 1.23
?ms/vX0 2.1 2.3 3.1
Cost //kg 3 0.2 2
All three media are readily available in
industrial quantities.
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Water Cherenkov

• Cheapest target medium (but not negligible with
  filtering and dopants)
• Only route to megaton instruments
• Well proven technology (IMB, Kam, SK)
• Excellent for mu/e separation 1 GeV.
• Electron scattering for solar nus.
• Threshold above 4 MeV gt no geonus or n-p
  captures. n detection needs Gd.
• No complex event topologies.

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Liquid Scintillation Detectors

• Hi resolution, low threshold (ltMeV)
• Technology well developed (50 years, plus
  Borexino, KamLAND and soon SNO)
• Excellent for anti-neutrino detection by inverse
  beta decay.
• Liquid too expensive beyond 100kT.
• New recognition GeV neutrino physics too.

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Liquid Argon TPC Detectors

• Bubble chamber-like imaging, detailed event
  topology, with few mm resolution.
• Developed over 30 years, and now being applied in
  600 ton Icarus in Gran Sasso.
• No free protons for nucleon decay or inverse beta
  studies.
• Only detector for potential discrimination of e
  from e- at neutrino factory.

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Energy Range of Interest
Large Underground Detectors
Accelerator Neutrinos
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Liquid Treatment

• All three require special facilities, all
  expensive and a bit hard to compare.
• Lesson of past do great job on first fill into
  superclean detector, have radon tight system, and
  do not have to recirculate much or at all.

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Muon Rates for 100 kiloton Detectors at Homestake
Depth/ft Depth/mwe Muon Rate/ 2150m2/sec
300 265 1616
1000 880 215
2600 2300 2.8
3350 2960 0.71
3950 3490 0.32
4100 3620 0.14
4850 4290 0.05
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Depth Requirements

• All depends upon physics goals
• Also depends upon detector size external
  backgrounds (eg. from muon showers in rock)
  worst for small instruments. Big detectors take
  hit near periphery.
• Great depth only needed for MeV measurements
  (geonus, low end of solar).
• PDK, accelerator studies, atm nus, SN, DSNB all
  can be done at much less depth exact depth
  arguable depending upon technique and physics.

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Rough Graphical Representation of Depth
Requirements
Many caveats required, but trend is correct...
jgl opinion
Depth/kmwe 0 H2O LS LAr
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2
3
4
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Long Baseline 1GeV ?s
Nucleon Decay
Supernova
No Background
Reactors
Diffuse SN Neutrinos
Geo-Neutrinos
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Nucleon Decay Predictions
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Nucleon Decay
L Ar LS H2O
43/2.25
1.0 x 1035
The ep0 estimate for LENA is based upon new
fitting methods.
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Supernova Rates
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Diffuse Supernova Neutrino Background
Better low energy atmospheric neutrino flux
calculations needed.
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Physics Summary Comparison Chart
Physics Scint Water Argon
PDK epi0 1.0E35 yr 1.0E35 yr 0.4E35 yr
PDK nu-K 0.4E35 yr 0.2E35 0.6E35
Free ps Yes Yes No
Relic Sn nus lt1/cm2 1/cm2 No
Solar nus Yes Yes Yes
PeP Yes Yes Yes
Geo nus Yes No No
SN burst 2E4 2E5 6e4
Ethresh lt1 MeV 4 MeV 1 MeV
Nucl Thresh 15 MeV 30 MeV 60 MeV
Reactor Nus Yes Iff Gd No
Reactor Hierarchy Yes No No
Reactor Theta13 Yes No No
Atm nus Yes Yes Yes
LBL e appear Yes Yes Yes
LBL e/e- No No Yes
Indir WIMPs Yes Yes Yes
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LAGUNA Seems to be on the map!
Who will win?
Plus Japan (HyperK). How will DUSEL fit into
this picture?
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Bottom Line

• Each has strengths
• Long range LAr wins for detailed neutrino
  physics in LBL, tho nice anytime
• Great sizes (megaton) H2O wins
• Low energies Liquid Scint wins (particularly for
  geonus)
• Cost/vol hierarchy LArLSH2O
• Readiness LS H2O gt LAr
• I like them all!!