1. What is the case for nufact? Hitoshi Murayama (UC Berkeley) Intl Scoping Study Meeting of Nufact and Superbeam Boston University, March 8, 2006

2. ISS Physics WS Boston2 The Question Neutrino physics has been full of surprises We’ve learned a lot in the last ~8 years We want to learn more New projects are more and more expensive Is it really worth it? Especially worth ~B$, B€, 100B¥?

3. ISS Physics WS Boston3 Elevator Pitch If you happen to be on an elevator with a powerful senator, can you explain why you want to spend ~B$ on your project in 30 seconds?

4. ISS Physics WS Boston4 What will NOT work For politicians and taxpayers, these arguments wouldn’t be convincing and/or interesting enough Measurements as precisely as we can Push limits on  13 as much as we can Verify the three-generation framework of neutrino oscillation Distinguish different flavor modles Field needs another machine to sustain itself

5. ISS Physics WS Boston5 Quantum Universe Report What are neutrinos telling us? Of all the known particles, neutrinos are the most mysterious. They played an essential role in the evolution of the universe, and their tiny nonzero mass may signal new physics at very high energies.

6. ISS Physics WS Boston6 Quantum Universe Report Einstein’s Dream of Unified Forces –Are there undiscovered principles of nature: new symmetries, new physical laws? –How can we solve the mystery of dark energy? –Are there extra dimensions of space –Do all the forces become one? The Particle World –Why are there so many kinds of particles? –What is dark matter? How can we make it in the laboratory? –What are neutrinos telling us? The Birth of the Universe –How did the universe come to be? –What happened to the antimatter?

7. ISS Physics WS Boston7 Outline Why Neutrinos? A few scenarios –sin 2 2  13 ≪ 0.01 –sin 2 2  13 > 0.01 –Mini-BooNE confirms LSND –LHC discovers new physics < TeV The Big Questions –Scenario to “establish” seesaw/leptogenesis Conclusion

8. Why Neutrinos?

9. ISS Physics WS Boston9 Interest in Neutrino Mass So much activity on neutrino mass already. Why are we doing this? Window to (way) high energy scales beyond the Standard Model!

10. ISS Physics WS Boston10 Why Beyond the Standard Model Standard Model is sooooo successful. But none of us are satisfied with the SM. Why? Because it leaves so many great questions unanswered  Drive to go beyond the Standard Model Two ways: –Go to high energies –Study rare, tiny effects 

11. ISS Physics WS Boston11 Rare Effects from High-Energies Effects of physics beyond the SM as effective operators Can be classified systematically (Weinberg)

12. ISS Physics WS Boston12 Unique Role of Neutrino Mass Lowest order effect of physics at short distances Tiny effect (m /E ) 2 ~(0.1eV/GeV) 2 =10 –20 ! Inteferometry (i.e., Michaelson-Morley) –Need coherent source –Need interference (i.e., large mixing angles) –Need long baseline Nature was kind to provide all of them! “neutrino interferometry” (a.k.a. neutrino oscillation) a unique tool to study physics at very high scales

13. ISS Physics WS Boston13 Ubiquitous Neutrinos They must have played some important role in the universe!

14. ISS Physics WS Boston14 The Data de Gouvêa ’ s classification: “Indisputable” –Atmospheric –Solar –Reactor “strong” –Accelerator (K2K) And we shouldn’t forget: “unconfirmed” –Accelerator (LSND)

15. ISS Physics WS Boston15 Historic Era in Neutrino Physics We learned: Atmospheric  s are lost. P=4.2 10 –26 (SK) (1998) converted most likely to  (2000) Solar e is converted to either  or  (SNO) (2002) Only the LMA solution left for solar neutrinos (Homestake+Gallium+SK+SNO) (2002) Reactor anti- e disappear (2002) and reappear (KamLAND) (2004)

16. ISS Physics WS Boston16 Neutrinos do oscillate!  Proper time 

17. ISS Physics WS Boston17 What we learned Lepton Flavor is not conserved Neutrinos have tiny mass, not very hierarchical Neutrinos mix a lot the first evidence for incompleteness of Minimal Standard Model Very different from quarks

18. ISS Physics WS Boston18 Typical Theorists’ View ca. 1990 Solar neutrino solution must be small angle MSW solution because it’s cute Natural scale for  m 2 23 ~ 10–100 eV 2 because it is cosmologically interesting Angle  23 must be ~ V cb =0.04 Atmospheric neutrino anomaly must go away because it needs a large angle Wrong!

19. ISS Physics WS Boston19 The I visibles

20. ISS Physics WS Boston20

21. ISS Physics WS Boston21 The Big Questions What is the origin of neutrino mass? Did neutrinos play a role in our existence? Did neutrinos play a role in forming galaxies? Did neutrinos play a role in birth of the universe? Are neutrinos telling us something about unification of matter and/or forces? Will neutrinos give us more surprises? Big questions  tough questions to answer

22. ISS Physics WS Boston22 Immediate Questions Dirac or Majorana? Absolute mass scale? How small is  13 ? CP Violation? Mass hierarchy? Is  13 maximal? LSND? Sterile neutrino(s)? CPT violation?

23. ISS Physics WS Boston23 Tools Available tools now: –SuperK, SNO, KamLAND, Borexino, Mini-BooNE, MINOS, Cuoricino, NEMO, SDSS, … Available soon (?): –Opera, Double-Chooz, T2K, MINER A, SciBooNE, NO A, reactor  13 expts, KATRIN, PLANCK, new photometric surveys, more 0  expts, … Do we really need more? What do we need?

24. ISS Physics WS Boston24 Do we really need more? What do we need? The answer depends on what we will find in the near future Talk about a few scenarios –sin 2 2  13 ≪ 0.01 –sin 2 2  13 > 0.01 –Mini-BooNE confirms LSND –LHC discovers new physics < TeV

25. sin 2 2  13 ≪ 0.01

26. ISS Physics WS Boston26 Obvious case? Superbeams will not address  13, mass hierarchy, or CP violation A clear case for neutrino factory and/or  - beam de Gouvêa: Will we get the funds to get a neutrino factory even if all previous investments end up “ unsuccessful ” ?

27. sin 2 2  13 >0.01

28. ISS Physics WS Boston28 sin 2 2  13 >0.01 Reactor/T2K/NO A finds sin 2 2  13 This is my prejudice Upgrades (4MW J-PARC to HyperK, Proton Driver+NO A 2nd detector, etc) –Measures sin 2 2  13 precisely –Determines mass hierarchy –Discovers CP violation What’s left then?

29. ISS Physics WS Boston29 The source of CP violation Having seen does not tell us what is causing it (in particular in the presence of “ matter effect background ” ) Is it due to the Dirac phase in the MNS matrix? Exactly the same question being addressed by B- factories –i.e.,  K can be explained by the KM phase, but is it? –Cross check in a different system, e.g., B  Yes! –Is there new interaction (e.g. SUSY loop)?  future

30. ISS Physics WS Boston30 Testing MNS hypothesis One way I know is to use tau modes Consequence of CPT and three flavors Can they be studied at neutrino factory? –I know it is tough even for a neutrino factory, but other facilities will clearly not do it

31. ISS Physics WS Boston31 Testing MNS hypothesis A simulation like this will make the case (e)(e) ()() (e)(e) ()() w/o new neutrino interactionwith new neutrino interaction

32. Mini-BooNE confirms LSND

33. ISS Physics WS Boston33 The hell breaks loose In this case, it is hard to understand what is going on, because there is currently no simple way to accommodate LSND result with other neutrino data –Multiple sterile neutrinos? –Sterile neutrino and CPT violation? –Mass varying neutrinos? –Something even more wild and wacky?

34. ISS Physics WS Boston34 What it takes We will need neutrino “oscillation” experiments with multiple baselines, multiple modes –E~10 GeV, L~10km, looking for  appearance –Redo CDHSW (  disappearance experiment with L=130 & 885m, E=19.2GeV) –E~1 GeV, L~1 km, looking for oscillatory behavior and CP violation in e  , or better,   e –Some in the air, some in the earth –Probably more –Muon source would help greatly

35. LHC discovers new physics <TeV

36. ISS Physics WS Boston36 TeV new physics Whatever it is, –SUSY, large extra dimensions, warped extra dimension, technicolor, Higgsless, little Higgs it is hard to avoid the TeV-scale physics to contribute to flavor-changing effects in general Renewed strong case for, e.g., super-B Very strong case for lepton flavor violation, g   2 –Hence, for a muon storage ring Obvious competition with ILC and beyond

37. ISS Physics WS Boston37 For example, SUSY High-energy data (LHC/ILC) will provide masses of superparticles –But most likely not their mixings Low-energy LFV experiments (e.g.,  e ,  A  eA) provide rates (T-odd asymmetry if lucky) –Combination of virtual particles in the loop and their mixing Put them together –Resolve the mixing –Constrain models of flavor

38. ISS Physics WS Boston38 What about the Big Questions? What is the origin of neutrino mass? Did neutrinos play a role in our existence? Did neutrinos play a role in forming galaxies? Did neutrinos play a role in birth of the universe? Are neutrinos telling us something about unification of matter and/or forces? Will neutrinos give us more surprises? Big questions  tough questions to answer

39. Origin of Neutrino Mass, our existence, even our universe

40. ISS Physics WS Boston40 Neutrinos must be Massless All neutrinos left-handed  massless If they have mass, can’t go at speed of light. Now neutrino right-handed??  contradiction  can’t be massive

41. ISS Physics WS Boston41 Two ways to go (1) Dirac Neutrinos: –There are new particles, right-handed neutrinos, after all –Why haven’t we seen them? –Right-handed neutrino must be very very weakly coupled –Why?

42. ISS Physics WS Boston42 Extra Dimensions All charged particles are on a 3-brane Right-handed neutrinos SM gauge singlet  Can propagate in the “bulk” Makes neutrino mass small m ~ 1/R if one extra dim  R~10  m An infinite tower of sterile neutrinos Or anomaly mediated SUSY breaking

43. ISS Physics WS Boston43 Two ways to go (2) Majorana Neutrinos: –There are no new light particles –Why if I pass a neutrino and look back? –Must be right-handed anti-neutrinos –No fundamental distinction between neutrinos and anti- neutrinos!

44. ISS Physics WS Boston44 Seesaw Mechanism Why is neutrino mass so small? Need right-handed neutrinos to generate neutrino mass To obtain m 3 ~(  m 2 atm ) 1/2, m D ~m t, M 3 ~10 15 GeV (GUT!), but R SM neutral

45. ISS Physics WS Boston45 Grand Unification electromagnetic, weak, and strong forces have very different strengths But their strengths become the same at 10 16 GeV if supersymmetry To obtain m 3 ~(  m 2 atm ) 1/2, m D ~m t  M 3 ~10 15 GeV! Neutrino mass may be probing unification: Einstein’s dream M3M3

46. ISS Physics WS Boston46 Leptogenesis You generate Lepton Asymmetry first. (Fukugita, Yanagida) Generate L from the direct CP violation in right-handed neutrino decay L gets converted to B via EW anomaly  More matter than anti-matter  We have survived “The Great Annihilation” Despite detailed information on neutrino masses, it still works (e.g., Bari, Buchmüller, Plümacher)

47. ISS Physics WS Boston47 Origin of Universe Maybe an even bigger role: inflation Need a spinless field that –slowly rolls down the potential –oscillates around it minimum –decays to produce a thermal bath The superpartner of right-handed neutrino fits the bill When it decays, it produces the lepton asymmetry at the same time (HM, Suzuki, Yanagida, Yokoyama) Decay products: supersymmetry and hence dark matter Neutrino is mother of the Universe? ~ amplitude size of the universe R

48. ISS Physics WS Boston48 Origin of the Universe Right-handed scalar neutrino: V=m 2  2 n s =0.96 r=0.16 Detection possible in the near future

49. ISS Physics WS Boston49 Can we prove it experimentally? Unfortunately, no: it is difficult to reconstruct relevant CP-violating phases from neutrino data But: we will probably believe it if the following scenario happens Archeological evidences

50. ISS Physics WS Boston50 A scenario to “establish” seesaw We find CP violation in neutrino oscillation –At least proves that CP is violated in the lepton sector U e3 is not too small –At least makes it plausible that CP asymmetry in right-handed neutrino decay is not unnaturally suppressed But this is not all

51. ISS Physics WS Boston51 A scenario to “establish” seesaw LHC finds SUSY, LC establishes SUSY no more particles beyond the MSSM at TeV scale Gaugino masses unify (two more coincidences) Scalar masses unify for 1st, 2nd generations (two for 10, one for 5*, times two)  strong hint that there are no additional particles beyond the MSSM below M GUT except for gauge singlets.

52. ISS Physics WS Boston52 Gaugino and scalars Gaugino masses test unification itself independent of intermediate scales and extra complete SU(5) multiplets Scalar masses test beta functions at all scales, depend on the particle content

53. ISS Physics WS Boston53 A scenario to “establish” seesaw Next generation experiments discover neutrinoless double beta decay Say,  m  ee ~0.1eV (quasi-degenerate) There must be new physics below  ~10 14 GeV that generates the Majorana neutrino mass

54. ISS Physics WS Boston54 A scenario to “establish” seesaw It leaves the possibility for R-parity violation Consistency between cosmology, dark matter detection, and LHC/ILC will remove the concern

55. ISS Physics WS Boston55 Preliminary High precision even for ILC  = 10 14 GeV seesawModified Type-I Type-II seesaw New particles 31313  24 15+15 * (m Q 2 -m U 2 )/M 1 2 11.2831.078 (m Q 2 -m E 2 )/M 1 2 11.0841.026 (m D 2 -m L 2 )/M 1 2 11.0401.014 Matt Buckley

56. ISS Physics WS Boston56 A scenario to “establish” seesaw B-mode fluctuation in CMB is detected, with a reasonable inflationary scale  strong hint that the cosmology has been ‘normal’ since inflation (no extra D etc)

57. ISS Physics WS Boston57 A scenario to “establish” seesaw Possible additional archeological evidence, e.g.,: lepton-flavor violation (  e conversion,  ) seen at the “reasonable” level expected in SUSY seesaw (even though I don’t believe mSUGRA) B d  K S shows deviation from the SM consistent with large b R -s R mixing above M GUT Isocurvature fluctuation seen suggestive of N 1 coherent oscillation, avoiding the gravitino problem

58. ISS Physics WS Boston58 Conclusions Revolutions in neutrino physics Neutrino mass probes rare/subtle/high-energy physics There is a very good chance for further big progress Most likely, we will need superbeam, and also neutrino factory and/or beta beam Neutrino physics is within the context of particle physics, astrophysics and cosmology Big questions can be answered only based on collection of experiments, not oscillation alone What’s the elevator pitch?