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Neutrino Physics

Neutrino Physics. Member Eriko kusunoki Kenji shu Takeshi saito Mesanori iwamoto Mitsutaka nakao. NISHIMURA Group. CONTENTS. ν - Source. Theory of Neutrino Physics Super Kamiokande (Super K) Measuring Cosmic Rays T2K Experiment Analyzing T2K data. ν - Oscillation.

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Neutrino Physics

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  1. Neutrino Physics Member Eriko kusunoki Kenji shu Takeshi saito Mesanoriiwamoto Mitsutakanakao NISHIMURA Group

  2. CONTENTS ν- Source • Theory of Neutrino Physics • Super Kamiokande (Super K) • Measuring Cosmic Rays • T2K Experiment • Analyzing T2K data ν- Oscillation ν- Detector

  3. Theory of Neutrino Physics

  4. What is neutrino? ・Three Flavors ・Neutral (no charge) ・Only Weak Interaction ・Very Tiny Mass very difficult for detecting…

  5. The interesting point is… Neutrino Oscillation

  6. Neutrino Oscillation(Two mixing case) ・The mass basis is different from the interaction basis. The probability to change νμinto ντis… ✔ flavour Θ:mixing angle L : Length [km] E : energy[GeV] Δm2 : mass square difference[eV2] mass ✔ ✔ but nature is more complex…

  7. Neutrino Oscillation(Three mixing case) ✔ ✔ ❓ ~45° ~34° Atmospheric Neutrinos νμ→ντ Solar Neutrinos νe→νx Accelerator νμ→νe What we want to know is … T2K Mixing Parameter

  8. CP violation~What is δCP in PMNS matrix?~ This parameter leads to CP violation. Leading Term CP term

  9. How can we detect neutrinos? The answer is… Super K

  10. Super-Kamiokande Kamioka 1km Inner tank 11,129 PMTs (50cm) detect neutrinos. 1km Underground We can block muonsthat originate from cosmic ray. 41.4m outer tank • 1,885 PMTs (20cm) • distinguish neutrinos from muons coming from outside. water 39.3m 50,000 t

  11. Neutrino detection @Super-Kamiokande inverse beta decay Neutrinos interact with particle in water. O n p • → SK detect Cherenkov light that is created when a charged particle travels faster than the speed of light in water. Cherenkov light H neutrino Blue : weak light Vertex Timing ofdetection Vertex position Finding Cherenkov ring Neutrino traveling direction and energy Red : strong light Event display

  12. ｅ Neutrino detectors Super-Kamiokande Next: Hyper-Kamiokande Metal dynode Improving performance (Volume of tank) ×25 • PMT (PhotoMultiplier-tube) • HPD (Hybrid-Photo‐Detector) To measure the light energy, we use PMTs. HK might uses HPDs instead of PMT. Let’s use HPD !!!! ~2kV Photon ｅ ｅ photoelectric effect Avalanche diode HPD accomplish superior performance in low cost !! ~8kV

  13. Testing PMTs and HPDs ThesePMT are used in super-K to measure the cosmic rays. HPDs may be used in Hyper-K . We tested an HPD and a PMT to measure the angular Distribution of cosmic ray muons . PMT HPD

  14. The Angular Distribution of Cosmic ray Muons The flux is given by J(x,θ) = J(x,0) (n = Where λ is mean free path The purpose of this experiment was finding the value of n.

  15. μ Scintillator(50cm×50cm) Set up We used two sets of two detectors to measure the angular distribution. Scintillator(20cm×20cm) HPD PMT PMT First detector Second detector

  16. We made a coincident circuit to count muons which activated all detectors.

  17. Results We corrected flux by a solid angle

  18. fitting We fitted a× and determined n = 2.470.53 .

  19. T2K Experiment

  20. What is T2K? • Tokai(J-PARC) to Kamioka(SK) • Pure • SK can distinguish and • Observe appearing and disappearing ? http://t2k-experiment.org/ja/

  21. Devices to discovery • Distance • Off axis (on axis) 。 2.5 appearensae in E = 0.6 GeV disappearing in L =295 km SK L = 295 km E ～ 0.6 GeV

  22. Enrichment signals • Selection one ring -like events • Reduce BG cuts using Monte Carlo calculations 377 events is first selected by timing 60 193 Number of rings e -like evernts cut NC,μ cut BG cut collapse π,μ cut in beam 57 44 39 28

  23. events -like single ring events were found • Proton created in J-PARC : • expected BG : 4.92 • So we calculate expectation and estimate Was happened? ? 6.57

  24. Analyzing T2K data

  25. What we have • T2K result number : Proton number : Very new : Physical Review Letters, 2014 Feb • Theory

  26. Maximum Likelihood Method to find • Likelihood function : ← maximize L • ← minimize Compare numbers obs. vs exp. Poisson distribution Restrict systematic parameters f : systematic errors ← parameters Expectation of numbers observed : signal of oscillation depends on ←par : background appeared as by M.C. simulation (depends on , , , function was given)

  27. Get • Best fit Change minimizing That = experimental result!!!

  28. Get errors • Error(1 sigma) → get at

  29. Get confidence level for → get at Significance : 6.9s actually exists and non-zero!!!

  30. Comparison with actual T2K Actual T2K Our verification C.L. : • C.L. : Same value, same error T2K was correct!!! (C.L. is better by using energy likelihood function)

  31. In actual T2K experiment… • Likelihood function : oscillation parameter : systematic error parameter f are more than 49!

  32. Future experiment • T2K is just in beginning • Continue to get 10 times more data • Check the sensitivity () (We did) → twice more precise • Anti-Neutrino experiment by Hyper-K can measure

  33. Summary Experiment Analyzing Theory

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