AntiNeutrino Simulations

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Anti-Neutrino Simulations

• And Elimination of Background Events
• Kansas State REU Program
• Author Jon Graves

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Topics

• What are neutrinos?
• How do we measure them?
• Double Chooz
• Fast neutrons
• Simulations and analysis
• Results
• Conclusion
• KamLAND
• Final Remarks

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What Are Neutrinos?

• Nearly massless
• Three flavors
• Mass oscillations
• Sources
• Fusion
• Fission
• CMBR
• Super Novae
• Cosmic Rays

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What Are Neutrinos?

• Reactions
• Neutron Transformation ---
• Proton Transformation
• Flavors
• Electron, Muon, Tau
• Detection yields 1/3 the value expected

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What Are Neutrinos?

• Sources
• Stars
• Radioactive Decay
• Nuclear Reactors
• Super Novae

View of the sun as seen in neutrinos. (Credit
Institute for Cosmic Ray Research, Tokyo)
Supernova 1987A
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How do we measure them?

• Anti-Neutrino - Proton interaction
• Prompt signal
• Positron/Electron annihilation
• -----

• Delayed signal
• Thermal neutron capture
• Gadolinium
• Hydrogen

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Double Chooz

• In northern France
• Cylindrical geometry
• Four volumes of interest
• Target
• Gamma-Catcher
• Buffer
• Inner Veto

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Double Chooz

• Target
• LS and Gd
• Used for capturing neutrons
• Gamma-Catcher
• LS only
• Used for detecting gammas from prompt and delayed
  events

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Double Chooz

• Buffer
• Mineral oil, a.k.a. Buffer oil
• Shields inner active volumes from accidental
  backgrounds
• U Th decay in PMTs
• PMTs line this volume
• Inner Veto
• Steel shield tags muons

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Fast neutrons

• My goals
• How does the detector geometry affect the
  neutrons?
• How does the surrounding rock affect the
  neutrons?
• How often do the neutrons correlate to neutrino
  events?

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Simulations and analysis

• Macro parameters
• Rock shell thickness
• Initial position of generated neutrons
• Fill of generated neutrons
• Number of events to simulate
• Geology

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Geology

• Rocks surrounding detector are simulated using
  the following elements
• Gd, Ti, Ni, Cr, Fe, K, N, Al, Si, C, O
• The following elements are quite common in
  northern France
• Mn, Na, Ca, H, P, Mg

• A report confirms these additions plus Cl.

Dominant Elements in Earths Crust
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Simulations and analysis

• My energy deposition program
• Plot histograms of
• Energy depositions within the detector
• Prompt/Delayed energies
• Time interval for prompt/delayed energies
• 1 to 100 microseconds
• Initial/Final positions of neutrons
• Provide data analysis output in an organized text
  format

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Results

• 10,000 events simulated, 4000.0mm rock thickness
• Target 2 statistical error
• Gamma-Catcher 6
• Buffer 17
• Inner Veto 74
• Most neutrons are absorbed by the steel shield
  and rocks
• No correlated events
• Should run 1,000,000 events for better error
  analysis

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PROBLEM!!
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Problem

• After running 1,000,000 events, discovered no
  correlations again.
• Further analysis revealed an improperly
  configured option in the macro for the simulator.
• Simulator was set to merge events shorter than
  1ms. This guarantees no correlations in the 1
  to 100?s window.

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Simulations and analysis

• Simulated 500,000 events with correctly
  configured macro at two different rock
  thicknesses.

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Results

• 400.0mm rock thickness
• Target 108 statistical error
• Gamma-Catcher 306
• Buffer 1445
• Inner Veto 6196
• 5.14 of deposition events occurred within the
  target and gamma-catcher volumes.
• 9 correlation events
• Eliminated all but 2 in final analysis due to
  multi-neutron events

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Results
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Results

• 4000.0mm rock thickness
• Target 32 statistical error
• Gamma-Catcher 63
• Buffer 271
• Inner Veto 1287
• 5.75 of deposition events occurred within the
  target and gamma-catcher volumes, similar to
  other thickness
• 2 correlation events
• Eliminated both in final analysis due to
  multi-neutron events
• 79.48 less events with a rock thickness 10 times
  greater.

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Results
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Conclusion

• Detector geometry (steel shield) and surrounding
  rocks are effective in blocking most high-energy
  neutrons.
• Neutron events rarely correlate to neutrino
  events. However, this must still be accounted
  for, considering neutrino events themselves are
  rare.
• Two to three per day, on average

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KamLAND

• Kamioka Liquid-scintillator Anti-Neutrino
  Detector
• Kamioka Mine in northwestern Japan (main island)
• Spherical geometry
• Duties involve monitoring equipment and ensuring
  everything is operating at peak efficiency.
• Hourly check

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Final Remarks

• Learned a great deal about programming,
  neutrinos, detectors, real-world experience.
• I made the right choice in choosing a career path
  involving high-energy physics.