0 American Physical Society MultiDivisional Neutrino Study DOE-OS Briefing January 7, 2005 Washington DC Stuart Freedman Boris Kayser

1 Super KamiokANDE PMT Matrix Part I Why study neutrinos?

A view of the Sun from 1 Km underground

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Ray Davis Pioneering venture in Neutrino Physics

5 E 2 = m 2 c 2 E 1 = m 1 c 2 B. Pontecorvo Neutrino Ocillations In the rest frame Boosted to the lab frame

6 Atmospheric Neutrinos

7 The SuperKamiokande Light- Water Cherenkov Detector

8 Solar Neutrino Experiments

9 Neutrino Flavor Composition of 8 B Flux SNO

10 Reactor Antineutrino Experiments LMA :  m 2 = 5.5x10 -5 eV 2 sin 2 2  = KamLAND

11 81  8 events if no oscillation 56 events observed MINOS (FNAL  Soudan) 2005 Terrestrial Version of Atmospheric Neutrino Experiment If no oscillation: 151  11 Observe: 108

12 KamLAND Is the Neutrino Spectrum Distorted?

13 Is there an oscillation effect

14 Observing the oscillations in the neutrino rest frame

15 LSND at Los Alamos

16 Excerpts from the Charge “…response to the remarkable recent series of discoveries in neutrino physics…” “…build on the 2002 long range plans developed by NSAC and HEPAP.” “…create a scientific roadmap for neutrino physics.” “…examine the broad sweep of neutrino physics…” “…move towards agreement on the next steps…” The Study will lay scientific groundwork for the choices that must be made during the next few years.

17 Neutrino Study Organization Chairpersons Solar and Atmospheric Neutrino Experiments Reactor Neutrino Experiments Superbeam Experiments and Development Neutrino Factory and Beta-Beam Experiments and Development Neutrinoless Double Beta Decay and Direct Searches for Neutrino Mass What Cosmology/Astrophysics and Neutrino Physics can Teach Each Other Theory Discussion Group Writing Committee Organizing Committee

18 APS Neutrino Study: Midcourse Correction April 1-2, 2004 Berkeley

19 US scientists participate in neutrino physics worldwide

20 Present US Program in Neutrino Physics NSF DOE NP/HEP DOE HEP DOE NP/HEP DOE NP DOE HEP NASA DOE HEP NSF NP DOE HEP NSF DOE NP

21 Many of the past experiments and many of the future experiments we feel are particularly important rely on suitable underground facilities. The availability of these facilities will be crucial to future neutrino research. Underground Facilities

22 SNO Part II The Story

23 What Have We Learned? What Do We Not Know?

24 Neutrino masses — There is some spectrum of 3 or more neutrino mass eigenstates i : (Mass) Mass (  )  m i From neutrino flavor change (oscillation) experiments, we have learned that —  Neutrinos have nonzero rest masses  Leptons mix

25 We do not know how many different neutrinos there are. Just 3, the partners of the 3 charged leptons?? If the Liquid Scintillator Neutrino Detector (LSND) experiment is confirmed, there are more than 3. If LSND is not confirmed, nature may contain only 3 neutrinos. Then, from the existing neutrino oscillation data, the neutrino spectrum looks like —

26 (Mass) or }  m 2 sol  m 2 atm }  m 2 sol  m 2 atm  m 2 sol = 8 x 10 –5 eV 2,  m 2 atm = 2.5 x 10 –3 eV 2 ~ ~ Normal Inverted

27 Grand Unified Theories relate the Leptons to the Quarks. is un-quark-like, and would probably involve a lepton symmetry with no quark analogue. A grand goal of elementary particle physics is to unify all the forces of nature into a single force. The Grand Unified Theories, which do this for all the forces of nature save gravity, favor —

28 When W +   + +  , the produced neutrino state |  > is |  > =  U*  i | i >. Neutrino of flavor  Neutrino of definite mass m i Unitary Leptonic Mixing Matrix Flavor-  fraction of i = | | 2 = |U  i | 2. e  e,   ,    e, , or  i Leptonic mixing —

29  m 2 atm e [|U ei | 2 ]  [|U  i | 2 ]  [|U  i | 2 ]    (Mass) 2  m 2 sol } Bounded by reactor exps. with L ~ 1 km From max. atm. mixing, From  (Up) oscillate but  (Down) don’t { { { In LMA–MSW, P sol ( e  e ) = e fraction of 2 From max. atm. mixing,    includes (  –  )/√2 From distortion of e (solar) and e (reactor) spectra

30 The Mixing Matrix  12 ≈  sol ≈ 32°,  23 ≈  atm ≈ 36-54°,  13 < 15°  would lead to P(    ) ≠ P(    ). CP But note the crucial role of s 13  sin  13. c ij  cos  ij s ij  sin  ij AtmosphericCross-Mixing Solar Majorana CP phases ~

31 Are Neutrinos the Reason We Exist? The universe contains Matter, but essentially no antimatter. Good thing for us: This preponderance of Matter over antimatter could not have developed unless the two behave differently. (CP) The observed difference between Quark and antiquark behavior, as described by the Standard Model, is inadequate. Could the interactions of Matter and antimatter with neutrinos provide the crucial difference? Matter Antimatter Poof!

32 There is a natural way in which they could. The most popular theory of why neutrinos are so light is the — See-Saw Mechanism N Very heavy neutrino Familiar light neutrino } { The heavy neutrinos N would have been made in the hot Big Bang.

33 If Matter and antimatter interact differently with these heavy neutrinos N, then we can have — Probability [ N  e - + … ] ≠ Probability [ N  e + + … ] Matter antimatter in the early universe. This phenomenon (leptogenesis) would have led to a universe containing unequal amounts of Matter and antimatter. In time, they would have decayed into lighter particles.

34 We cannot repeat the early universe. But we can lend credibility to the hypothesis of leptogenesis by showing that Matter and antimatter interact differently with the light neutrinos. Source Detector e-e- -- Source Detector e+e+ ++ A neutrino flavor change involving Matter : A neutrino flavor change involving antimatter : If these two flavor changes have different probabilities, then quite likely so do — N  e - + … andN  e + + …

35 If N decays led to the present preponderance of Matter over antimatter, then we are all descendants of heavy neutrinos.

In Pursuit of  13 Both CP violation and our ability to tell whether the spectrum is normal or inverted depend on  13. How may  13 be measured? If sin 2 2  13 < 0.01, a neutrino factory will be needed to study both of these issues.

37  m 2 atm    (Mass) 2  m 2 sol } sin 2  13 is the small e piece of 3. 3 is at one end of  m 2 atm.  We need an experiment sensitive to  m 2 atm, and involving e. sin 2  13

38 Complementary Approaches Reactor e disappearance while traveling L ~ 1.5 km. L/E ~ 500 km/GeV. This process depends on  13 alone. Accelerator   e while traveling L > Several hundred km. L/E ~ 400 km/GeV. This process depends on  13 and other neutrino properties, including whether the spectrum is normal or inverted.

39 How To Determine If The Spectrum Is Normal Or Inverted In the experiments we will do with earth-born neutrinos, the neutrinos will travel through earth matter. Exploit the fact that, in matter, e – e interactions raise the effective mass of e.

40  m 2 atm e      (Mass) 2  m 2 sol }   m 2 atm    m 2 sol } vs. sin 2  13 If  m 2 atm shrinks (grows) in matter,  13 grows (shrinks).

41 The effect of matter increases as the neutrino distance of travel within it, L, does. Using larger L to determine whether the spectrum is normal or inverted could be a unique contribution of the U.S. program.

42 Does — i = i (Majorana neutrinos) or i ≠ i (Dirac neutrinos) ? e + ≠ e – since Charge(e + ) = – Charge(e – ). But neutrinos may not carry any conserved charge-like quantum number. A conserved Lepton Number L defined by— L( ) = L( – ) = –L( ) = –L( + ) = 1 may not exist. If it does not, then i = i  and we can have — Are Neutrinos Their Own Antiparticles?

43 Neutrinoless Double Beta Decay (0  ) Observation would establish that — Lepton number L is not conserved Neutrinos are Majorana particles ( = ) The origin of neutrino mass is not the same as the origin of the masses of charged leptons, quarks, nucleons, humans, the earth, galaxies i i W–W– W–W– e–e– e–e– Nuclear Process Nucl Nucl’ Then neutrinos and their masses are very distinctive.

44 The Quest for the Origin of Mass Neutrino experiments and the search for the Higgs boson both probe the origin of mass. The see-saw mechanism suggests that the physics behind neutrino mass resides at GeV, the extremely high energy where Grand Unified Theories say all the forces of nature, save gravity, become one.

45 The Open Questions

46 Neutrinos and the New Paradigm What are the masses of the neutrinos? What is the pattern of mixing among the different types of neutrinos? Are neutrinos their own antiparticles? Do neutrinos violate the symmetry CP?

47 Neutrinos and the Unexpected Are there “sterile” neutrinos? Do neutrinos have unexpected or exotic properties? What can neutrinos tell us about the models of new physics beyond the Standard Model?

48 Neutrinos and the Cosmos What is the role of neutrinos in shaping the universe? Is CP violation by neutrinos the key to understanding the matter – antimatter asymmetry of the universe? What can neutrinos reveal about the deep interior of the earth and sun, and about supernovae and other ultra high energy astrophysical phenomena?

49 KamLAND Part III Recommendations for future experiments

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KATRIN ’04 ’05 ’06 ’07 ’08 ’09 ’10 ’11 ’12 ’13 ’14 ’15 ’16 ’17 ’18 ’19 ’20 Running Existing Program Signal? MINOS RunningConstr. 7 Be Solar US Based US Participation KamLAND Reactor MiniBooNE Super-K + K2K+T2K HE Astro SNO Running Constr.Running R&D ConstructionRunning ConstructionRunning Green < $10M/yr Blue $10M - $40M/yr Orange $40M -$100M/yr Red > $100M/yr

New Experiments RunningConstructionR&D Constr.Running R&DConstructionRunning R&DConstr.Running R&D ConstructionRunning R&D No Signal? 1 ton  pp Solar Reactor Long Baseline 200 kg  Construction/Running Cross Sections ’04 ’05 ’06 ’07 ’08 ’09 ’10 ’11 ’12 ’13 ’14 ’15 ’16 ’17 ’18 ’19 ’20 Green < $10M/yr Blue $10M - $40M/yr Orange $40M -$100M/yr Red > $100M/yr New Experiments

Proton driver R&D Construction Running R&D Facilities R&DConstructionRunning Construction R&D Multipurpose Detector UG Lab Factory Running ’04 ’05 ’06 ’07 ’08 ’09 ’10 ’11 ’12 ’13 ’14 ’15 ’16 ’17 ’18 ’19 ’20 Const. Facilities Green < $10M/yr Blue $10M - $40M/yr Orange $40M -$100M/yr Red > $100M/yr

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