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Anti-Neutrino Simulations

Anti-Neutrino Simulations. And Elimination of Background Events Kansas State REU Program Author: Jon Graves. Topics. What are neutrinos? How do we measure them? Double Chooz Fast neutrons Simulations and analysis Results Conclusion KamLAND Final Remarks. What Are Neutrinos?.

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Anti-Neutrino Simulations

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  1. Anti-Neutrino Simulations And Elimination of Background Events Kansas State REU Program Author: Jon Graves

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

  3. What Are Neutrinos? • Nearly massless • Three “flavors” • Mass oscillations • Sources • Fusion • Fission • CMBR • Super Novae • Cosmic Rays

  4. What Are Neutrinos? • Reactions • Neutron Transformation ---> • Proton Transformation • Flavors • Electron, Muon, Tau • Detection yields 1/3 the value expected

  5. 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

  6. How do we measure them? • Anti-Neutrino -> Proton interaction • Prompt signal • Positron/Electron annihilation -----> • Delayed signal • Thermal neutron capture • Gadolinium • Hydrogen

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

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

  9. 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

  10. 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?

  11. Simulations and analysis • Macro parameters • Rock shell thickness • Initial position of generated neutrons • Fill of generated neutrons • Number of events to simulate • Geology

  12. 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 Earth’s Crust

  13. 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

  14. Results • 10,000 events simulated, 4000.0mm rock thickness • Target = 2 <------70.7% relative 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

  15. PROBLEM!!

  16. 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.

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

  18. Results • 400.0mm rock thickness • Target = 108 <------9.6% relative 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

  19. Results

  20. Results • 4000.0mm rock thickness • Target = 32 <------17.7% relative 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.

  21. Results

  22. 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

  23. 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

  24. 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.

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