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Neutrinos: Results and Future

Neutrinos: Results and Future. Boris Kayser DESY March 4, 2008. Evidence For  Flavor Change. Neutrinos Solar Reactor (L ~ 180 km) Atmospheric Accelerator (L = 250 and 735 km) Stopped  + Decay LSND L  30 m. Evidence of Flavor Change Compelling Compelling Compelling

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Neutrinos: Results and Future

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  1. Neutrinos: Results and Future Boris Kayser DESY March 4, 2008

  2. Evidence For  Flavor Change • Neutrinos • Solar • Reactor(L ~ 180 km) • Atmospheric • Accelerator(L = 250 and 735 km) • Stopped + Decay LSND L  30 m • Evidence of Flavor Change • Compelling • Compelling • Compelling • Compelling • Unconfirmed by MiniBooNE ) (

  3. The neutrino flavor-change observations imply that — Neutrinos have nonzero masses and that — Leptons mix.

  4. What We Have Learned

  5. 3 3 m2atm 2 2 m2sol m2sol } } 1 1 The (Mass)2 Spectrum or (Mass)2 m2atm Inverted Normal ~ ~ m2sol = 7.6 x 10–5 eV2, m2atm = 2.4 x 10–3 eV2

  6. Rapid oscillation reported by LSND —  1eV2 in contrast to m2atm = 2.4 x 10–3 eV2 > m2sol = 7.6 x 10–5 eV2 At least 4 mass eigenstates. Are There More Than 3 Mass Eigenstates? When only two neutrinos count,

  7. MiniBooNE Search for   e R.Tayloe at LP07 • No excess above background for energies E > 475 MeV. • Unexplained excess for E < 475 MeV. • Two-neutrino oscillation cannot fit LSND and MiniBooNE. • More complicated fits are possible.

  8. MiniBooNE in the NuMI Beam The MiniBooNE detector is illuminated by boththe MiniBooNE  beam, and the NuMI  beam pointed at MINOS. Distance to MiniBooNE — L (from NuMI source)  1.4 L (from MiniBooNE source) Neutrino oscillation depends on L and E only through L/E. Therefore, if an anomaly seen at some E in the MiniBooNE-beam data is due to oscillation, it should appear at 1.4 E in the NuMI-beam data.

  9. e CCQE sample:Reconstructed energy E of incoming  Outgoing electron angular distribution (Z. Djurcic, Dec. 11, 2007) PRELIMINARY All e All 

  10. To be continued … Meanwhile, we will assume there are only 3 neutrino mass eigenstates.

  11. Leptonic Mixing • This has the consequence that — • |i> =  Ui |> . • Flavor- fraction of i = |Ui|2 . • When a i interacts and produces a charged lepton, the probability that this charged lepton will be of flavor  is |Ui|2 . Mass eigenstate Flavor eigenstate  e, , or  PMNS Leptonic Mixing Matrix

  12. sin213 2 3 } m2sol 1 m2atm or (Mass)2 m2atm 2 } m2sol 3 1 sin213 [|Ui|2] [|Ui|2] e [|Uei|2] The spectrum, showing its approximate flavor content, is Inverted Normal

  13. The Mixing Matrix Solar Atmospheric Cross-Mixing cij cos ijsij sin ij Majorana CP phases 12 ≈ sol ≈ 34°,23 ≈ atm ≈ 37-53°, 13 < 10°  would lead to P() ≠ P().CP But note the crucial role of s13 sin 13. ~

  14. From talk by N. Saoulidou “Atmospheric” m2 and mixing angle from MINOS, Super-K, and K2K.

  15. ) 2 eV ( sol 2 m D Presented by KamLAND, a reactor e experiment. “Solar” m2 and mixing angle from KamLAND and solar experiments.

  16. KamLAND Evidence for Oscillation L0 = 180 km is a flux-weighted average travel distance. P(e  e) actually oscillates!

  17. 7Be Solar Neutrinos Until recently, only the 8B solar neutrinos, with E  7 MeV, had been studied in detail. The Large Mixing Angle MSW (matter) effect boosts the fraction of the 8B solar e that get transformed into neutrinos of other flavors to roughly 70%. At the energy E = 0.862 MeV of the 7Be solar neutrinos, the matter effect is expected to be very small. Only about45% of the 7Be solar e are expected to change into neutrinos of other flavors.

  18. Borexino — Detects the 7Be solar neutrinos via e  e elastic scattering. Event rate (Counts/day/100 tons) Observed: 47  7(stat)  12(syst) Expected (No Osc): 75  4 Expected (With 45% Osc): 49  4 Expected (With 70% Osc): ~ 31

  19. The Open Questions

  20. What is the absolute scale of neutrino mass? • Are neutrinos their own antiparticles? • Are there “sterile” neutrinos? We must be alert tosurprises!

  21. What is the pattern of mixing among the different types of neutrinos? • What is 13? • Is the spectrum like or ? • Do neutrino – matter interactions violate CP? Is P( )  P( ) ?

  22. What can neutrinos and the universe tell us about one another? • Is CP violation involving neutrinos the key to understanding the matter – antimatter asymmetry of the universe? • What physics is behind neutrino mass?

  23. The Importance of Some Questions, and How They May Be Answered

  24. Does  = ? That is, for each mass eigenstatei does — • i = i (Majorana neutrinos) • or • i ≠ i (Dirac neutrinos) ? Equivalently, do neutrinos haveMajorana masses? If they do, then the mass eigenstates are Majorana neutrinos.

  25. Majorana Masses Out of, say, a left-handed neutrino field, L, and its charge-conjugate, Lc, we can build a Majorana mass term — ()R L mLLLc X mL Quark and charged-lepton Majorana masses are forbidden by electric charge conservation. Neutrino Majorana masses would make the neutrinos very distinctive.

  26. The objects L and Lcin mLLLcare not the mass eigenstates, but just the neutrinos in terms of which the model is constructed. mLLLcinduces LLc mixing. As a result of K0 K0 mixing, the neutral K mass eigenstates are — KS,L  (K0  K0)/2 . KS,L = KS,L . As a result of LLc mixing, the neutrino mass eigenstate is — i = L+Lc = “+  ”. i = i.

  27. To Determine If Neutrinos Have Majorana Masses

  28. e– e– Nucl’ Nucl The Promising Approach — Neutrinoless Double Beta Decay[0] We are looking for a small Majorana neutrino mass. Thus, we will need a lot of parent nuclei (say, one ton of them).

  29. e– e– ()R L 0 u d d u W W ()R L : AMajorana mass term  0i = i Whatever diagrams cause 0, its observation would imply the existence of aMajorana mass term: Schechter and Valle

  30. The Central Role of 13 If sin2213 > 10–(2-3), we can study both of these issues with intense but conventional accelerator  and  beams, produced via +  + +  and –  – +  . Both CP violation and our ability to tell whether the spectrum is normal or inverted depend on 13. Determining 13 is an important step.

  31. How 13 May Be Measured Reactor neutrino experiments are the cleanest way. Accelerator neutrino experiments can also probe 13 . Now it is entwined with other parameters. In addition, accelerator experiments can probe whether the mass spectrum is normal or inverted, and look for CP violation. All of this is done by studying   e and   e while the beams travel hundreds of kilometers.

  32. The Mass Spectrum: or ? Generically, grand unified models (GUTS) favor — GUTS relate the Leptons to the Quarks. is un-quark-like, and would probably involve a lepton symmetry with no quark analogue.

  33. Note fake CP How To Determine If The Spectrum Is Normal Or Inverted Exploit the fact that, in matter, ( ) e e W ( ) e e affects  and  oscillation (differently), and leads to — P( e) > 1 ; < 1 ; P( e) Note dependence on the mass ordering

  34. Spin Spin Q: Does matter still affect  and  differently when  = ? A: Yes! e+ “”   W+ e– “”   W– The weak interactions violate parity. Neutrino – matter interactions depend on the neutrino polarization.

  35. The observed CP in the weak interactions of quarks cannot explain theBaryon Asymmetry of the universe. Is leptonic CP, throughLeptogenesis, the origin of theBaryon Asymmetry of the universe? Do Neutrino Interactions Violate CP? ( ) Wilfried Buchmueller Leading contributor (Fukugita, Yanagida)

  36. { Familiar light neutrino  } Very heavy neutrino N The very heavy neutrinos N would have been made in the hot Big Bang. Leptogenesis In Brief The most popular theory of why neutrinos are so light is the — See-Saw Mechanism (Yanagida; Gell-Mann, Ramond, Slansky; Minkowski)

  37. The heavy neutrinos N, like the light ones , are Majorana particles. Thus, an N can decay into l or l+. If neutrino oscillation violates CP, then quite likely so does N decay. In the See-Saw, these two CP violations have a common origin. Then, in the early universe, we would have had different rates for the CP-mirror-image decays – Nl + … and Nl + … This would have led to unequal numbers of leptons and antileptons (Leptogenesis). Then, Standard-Model Sphaleron processes would have turned  1/3 of this leptonic asymmetry into a Baryon Asymmetry. +

  38. Look forP( )  P( ) How To Search for CP In Neutrino Oscillation

  39. i Ui* Uei i Ui Uei* Q : Can CP violation still lead to P(  e) P(  e) when  = ? A:Certainly!  e Compare + e–  Detector + with “  e ” e+ –  Detector –

  40. Separating CP From the Matter Effect Genuine CP and the matter effect both lead to a difference between  and  oscillation. But genuine CP and the matter effect depend quite differently from each other on L and E. One can disentangle them by making oscillation measurements at different L and/or E.

  41. CP-odd interference Atmospheric CP-even interference Solar = with   –  and x  – x. ) ( Accelerator  Oscillation Probabilities With , , and — ; , , , (Cervera et al., Freund, Akhmedov et al.)

  42. At fixed L/E, genuine CP effects do not change with E, but the matter effect grows, enhancing(suppressing) the oscillation if the hierarchy is Normal(Inverted). Strategies The matter-effect parameter xhas E/12 GeV. At L/E of the 1st “atmospheric” oscillation peak, and E 1 GeV, the effect of matter on the neutrino atmospheric oscillation term (sin2213T1) is — Normal Inverted

  43. If E E/3 at fixed L, we go from the 1st atmospheric oscillation peak to the 2nd one. When E E/3 at fixed L, CP is tripled,butthe matter effect is reduced by a factor of 3.

  44. Neutrino Vision at Fermilab

  45. Develop a phased approach with ever increasing beam intensities and ever increasing detector capabilities Probe Mixing, Mass Ordering, CP Violation Y-K Kim

  46. The Intensity Frontier With Project X Y-K Kim National Project with International Collaboration NuMI (NOvA) 8 GeV ILC-like Linac DUSEL Recycler: 200 kW (8 GeV) for kaons, muons, … Main Injector: 2.3 MW (120 GeV) for neutrinos Project X = 8 GeV ILC-like Linac + Recycler + Main Injector

  47. Project X: Properties (Young-Kee Kim) ~2.3 MW at 120 GeV for Neutrino Science Initially NOvA, Possibly DUSEL later 200 kW at 8 GeV for Precision Physics 8 GeV H- Linac with ILC Beam Parameters (9mA x 1msec x 5Hz) v < c v = c (ILC Linac)

  48. (Y-K Kim)

  49. Present: MINOS (200 kW, 120 GeV) • MINOS: • best measurement of Dm223 • provide an early glimpse on q13 • MiniBooNE, SciBooNE: • probe neutrino parameters • measure neutrino x-sections Booster Accumulator Debuncher MiniBooNE SciBooNE Recycler Main Injector Tevatron Y-K Kim

  50. Phase 1: MINOS MINERvA NOvA (700 kW, 120 GeV) • NOvA: • provide the first glimpse of the • mass hierarchy for large q13 - the only • near term probe of hierarchy in the world • excellent sensitivity to q13 • MINERvA: • measure neutrino x-sections • (above 1 GeV) to high precision Booster Recycler Main Injector Y-K Kim

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