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? Fast neutrons
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 Flavors
Neutron Transformation --->
Proton Transformation
Flavors
Electron, Muon, Tau
Detection yields 1/3 the value expected

5. What Are Neutrinos? Sources Stars Radioactive Decay Super Novae
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 Gamma-Catcher LS and Gd
Used for capturing neutrons
Gamma-Catcher
LS only
Used for detecting gammas from prompt and delayed events

9. Double Chooz Buffer Inner Veto 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 = < % 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 = < % 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 = < % 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.