Geoneutrino Radiometric Analysis for Geosciences

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Geoneutrino Radiometric Analysisfor Geosciences
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Geoneutrino working groupA collaboration among
Geochemistry,Geophysics and Nuclear Physics

• Group Leader P. ILA
• Geochemistry F. Frey, W. McDonough
• Geophysics W. Gosnold
• Physics G. I. Lykken, N. Tolich,
• T. Weinbeck?, Jagam,
  A. Bernstein?
• Nuclear Engineering R. Pevey

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Objectives Considerations - 1

• We propose an antineutrino detector at DUSEL
  Homestake mine to study antineutrinos from the
  Earths crust and mantle.
• Two alternatives to more precisely constrain the
  mantle contribution are
• a detector distant from the continental crust
  (e.g. the proposed Hanohano submarine detector
  near Hawaii)
• or a detector on the continental crust where the
  local U and Th abundances are well known.
• (Ref. Fiorentini et. al, Enomoto et. al )

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Objectives Considerations - 2

• Homestake is an excellent location for the second
  alternative because of
• the detailed information on the local U and Th
  content
• the extremely low contribution of electron
  antineutrinos from nuclear power plants.
• Combined with a measurement at another site like
  SNO we could test our models of the contribution
  from the continental crust.
• The detection of geoneutrinos will provide
  constraints on alternative models for the
  abundances of U and Th in the bulk Earth.

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Initial step

• To determine U and Th mass of 500 km radius half
  sphere beneath Homestake.
• This can be done by using existing and to be
  acquired data on Th and U contents of surficial
  rocks and core from the mine combined with
  seismic data to extrapolate to depth.

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Experimental Plan

• We plan to evaluate two alternative detector
  designs
• Modular (1 M3 modules upto 1000 modules?)
• Single large detector (1000 modules).
• We will weigh the pros and cons of these
  alternatives like
• Large detectors have lower backgrounds, fully
  contained events
• Modular detectors have flexible detector geometry
  and cosmic ray backgrounds can be evaluated by
  placing the detectors at different locations.

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Evaluation of M3 detector

• M3 detector was used in a surficial environment
  with minimal shielding.
• (Ref. Bowden et al. NIM A 572 (2007) 985
  -998)
• It detected events near a power reactor with
  power ON and OFF
• With the reactor OFF there was a reduced signal.
• The origin of events detected with the reactor
  off are in question.

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Evaluation of M3 detector

• They could be geoneutrinos, unvetoed cosmic ray
  events, or residual artifacts.
• Our plan is to bring the existing M3 detector
  underground and understand the relative role of
  backgrounds in geoneutrino studies.

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Experimental Plan

• To determine U and Th abundance of 500 km radius
  half sphere beneath Homestake.
• This can be done by using existing, and to be
  acquired, Th and U contents of surficial rocks
  and core from the mine combined with seismic data
  to extrapolate to depth.

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• Thank You