Neutrino Oscillations in vacuum

1. Neutrino Oscillations in vacuum Student Seminar on Subatomic Physics Fundamentals of Neutrino Physics Dennis Visser 15-10-2010

2. Outline 1. Plane wave derivation of neutrino oscillation probabilities 2. Wave packet treatment 3. Averaged oscillation probabilities 4. The KamLAND experiment 5. Additional topics (given time)

3. Plane wave derivation 7.4 7.10 def 7.21 We have assumed that all neutrinos have equal momenta and we define: 7.17 7.8 7.19 7.20 def We also assume that neutrinos propagate with the speed of light: 7.23

4. Plane wave derivation 7.23 Consider two-neutrino mixing 7.67 Amount of mixing Oscillation term because of the mass difference

5. Wave packet treatment WHY ? Consider the decay process In principle it is possible to know the energy and momentum of the neutrino from experiment, but even when we know them exactly … Heisenberg uncertainty relation:

6. Wave packet treatment WHY ? 1. Heisenberg uncertainty relation: → Neutrinos described by wave packets 2. Different massive neutrinos have different velocities → Different massive neutrino wave packets only detected coherently when the baseline is small enough

7. Wave packet treatment Fig. 8.2 When different masssive neutrinos in general not detected coherently

8. Wave packet treatment Fig. 8.3 When different masssive neutrinos in general not detected coherently

9. Wave packet treatment Natural Linewidth: 8.128 Particle decaying at rest: 8.129 Particle decaying in flight: 8.130

10. Wave packet treatment Due to the velocity difference between the two massive neutrinos For reactor neutrinos: [5] Lcoh >> baseline L, implying that one can neglect the wave packet effects for reactor neutrinos (for supernova neutrinos this is not true, Lcoh << baseline L)

11. Averaged oscillation probabilities Beside the averaging of the oscillation probabilities because of the wavepacket nature of neutrinos, there is also need for averaging the oscillation probabilities because for example: - Energy resolution of the detector is finite - Propagation distance not exactly known 7.93

12. Averaged oscillation probabilities 7.93 7.94 7.95 7.96

13. Averaged oscillation probabilities 7.93 7.96 Let’s consider the case

14. Averaged oscillation probabilities 1. Averaged oscillation probabilities because of the wave packet nature of neutrinos: 2. Averaged oscillation probabilities because of experimental uncertainties: Note that we have assumed For reactor neutrinos only experimental uncertainties important

15. Averaged oscillation probabilities Fig 7.2

16. Averaged oscillation probabilities Assume that from an experiment we have an upper limit for the transition probability: Then: → EXCLUSION PLOT Fig 7.3

17. Averaged oscillation probabilities Exclusion plot for a disappearance experiment 7.109 EXCLUDED REGION (lower bound) Fig. 7.4 b

18. Averaged oscillation probabilities (bounds) EXCLUDED REGION EXCLUDED REGION Fig 7.5 a

19. Averaged oscillation probabilities (measured) (measured) Fig 7.5 b

20. Averaged oscillation probabilities Dotted curve: best fit values: Fig 12.3

21. The KamLAND experiment Ref.[3]

22. The KamLAND experiment Ref.[3]

23. The KamLAND experiment Balloon filled with 1000 tons of liquid scintillator, acting as both the target and detection volume Surrounded by 1879 PMTs mounted on a steel sphere Volume between balloon and steel spere filled with non-scintillating mineral oil acting as a shield from external neutron and gamma radiation 20 m Volume between the steel sphere and the rock has a third layer, filled with water with PMTs mounted on the cylindrical surface on the outside KamLAND. This final layer uses Cherenkov radiation to detect muons passing through the detector. The muons can interact with the material in the central detector producing background radiation. By knowing exactly when a muon passes through KamLAND, the detector volume can be vetoed, to avoid detecting the background. Ref.[2]

24. The KamLAND experiment Ref.[6]

25. The KamLAND experiment Ref.[4]

26. The KamLAND experiment Ref.[4]

27. Summary • Neutrino flavor eigenstates not equal to neutrino mass eigenstates, this implies that neutrinos oscillate • Neutrinos described by wave packets, wave packet description is important when the baseline is large • Plane wave derivation valid for small L/E ratio • To explain results for large L/E ratio we need to average over an appropriate distribution of L/E, because of experimental uncertainties and/or wave packet effects. For large L/E ratio neutrinos are detected incoherently • Neutrino experiments give exclusion plots in the plane • Neutrino experiments are not that easy • From the KamLand experiment + solar experiment we have obtained precise values for one of the oscillation angles and one of the mass differences

28. References [1]Carlo Giunti and Chung W. Kim, Fundamentals of Neutrino Physics and Astrophysics, Oxford University Press, 2007 [2] KamLAND website, http://kamland.lbl.gov [3] Koichi Ichimura, Recent Result from KamLAND, presentation givenat ICHEP08 [4] Patrick Decowski, KamLAND Neutrino Oscillation Results and Solar Future, presentation given at Neutrino 2008 [5] C.W. Kim, Neutrino Physics: Fundamentals of Neutrino Oscillations, hep-ph/9607391, 1996 [6] The KamLAND Collaboration, Precision Measurement of Neutrino Oscillation Parameters with KamLAND, hep-ex/0801.4589, 2008

29. Additional topics

30. Oscillation probabilities 7.23 7.30 7.38

31. Antineutrino oscillation probabilities 7.49 7.50 7.51

32. CPT & CP transformations 7.53 7.56 CPT is assumed to be conserved in SM 7.57 7.59 7.61 7.62 7.63

33. Mass spectrum Fig 13.1 13.5 13.6

34. Mass spectrum Assume that 13.13 Then: 13.14 13.15 13.16

35. Mass spectrum Now assume that 13.18 Then: 13.19 13.20 13.21

36. Mass spectrum 13.22 13.8