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Dark Matter and Dark Energy by yurtgc548

VIEWS: 2 PAGES: 61

									Origin of Neutrino Mass


Hitoshi Murayama (UC Berkeley)
Neutrinos in Cosmology, in Astro,
  Particle and Nuclear Physics
   Erice, 17th September, 2005
                   Outline

•   Introduction
•   Implications of Neutrino Mass
•   Seven Questions
•   Why do we exist?
•   Models of Flavor
•   Conclusion

                     Erice 2005     2
Introduction
             The Question

• So much activity on neutrino mass already.
          Why are we doing this?
     Window to (way) high energy scales
        beyond the Standard Model!




                    Erice 2005                 4
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        
                       Erice 2005              5
Rare Effects from High-Energies

• Effects of physics beyond the SM as
  effective operators

• Can be classified systematically (Weinberg)




                     Erice 2005                 6
  Unique Role of Neutrino Mass
• Lowest order effect of physics at short distances
• Tiny effect (mn/En)2~(eV/GeV)2=10–18!
• 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           Erice 2005                      7
Ubiquitous Neutrinos




        Erice 2005     8
Sun as a neutrino source




      SuperK image of the Sun
            Erice 2005          9
We don’t get enough

                    We need survival
                    probabilities of
                    8B:   ~1/3
                    7Be:   <1/3
                    pp: ~2/3
                    Can we get three
                    numbers
                    correctly with
                    two parameters?
       Erice 2005                 10
             Year of Neutrino: 2002

March 2002

April 2002
with SNO

Dec 2002
with KamLAND




                      Erice 2005      11
   Solar Neutrino Problem
Finally Solved After 35 Years!
Historic Era in Neutrino Physics
We learned:
• Atmospheric nms are lost. P=4.2 10–26 (SK)
• converted most likely to nt
• Solar ne is converted to either nm or nt (SNO)
• Reactor anti-ne disappear and reappear (KamLAND)
• Only the LMA solution left for solar neutrinos
• Neutrinos have tiny but finite mass
                    the first evidence for
        incompleteness of Minimal Standard Model

                          Erice 2005                 13
                CP Violation
                                               2
 P(n e  n m )  P(n e  n m )  16s12 c12 s13c13 s23c23
            Dm2   Dm 2   Dm2 
 sin  sin  12 L sin  13 L sin  23 L
            4E   4E   4E 
• Possible only if:
  – Dm122, s12 large enough (LMA)
  – q13 large enough
• Can we see CP violation?
                         Erice 2005                        14
Typical Theorists’ View ca. 1990
• Solar neutrino solution must be small angle
  MSW solution because it’s cute           Wrong!
• Natural scale for Dm223 ~ 10–100 eV2
                                           Wrong!
  because it is cosmologically interesting
• Angle q23 must be ~ Vcb =0.04           Wrong!
• Atmospheric neutrino anomaly must go Wrong!
  away because it needs a large angle


                    Erice 2005               15
Implications of Neutrino Mass
Neutrinos are Left-handed




          Erice 2005        17
    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
                   Erice 2005                  18
           Standard Model
• We have seen only left-handed neutrinos
  and right-handed anti-neutrinos (CPT)
• Neutrinos are strictly massless in the
  Standard Model
  Finite mass of neutrinos implies that the
  Standard Model is incomplete!
• Not just incomplete but probably a lot more
  profound
                    Erice 2005              19
Mass Spectrum




What do we do now?
      Erice 2005     20
                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?
                          Erice 2005   21
                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
  (Arkani-Hamed, Dimopoulos, Dvali, March-Russell;
  Dienes, Dudas, Gherghetta; Grossman, Neubert)
• mn ~ 1/R if one extra dim  R~10mm
• An infinite tower of sterile neutrinos
• Or anomaly mediated SUSY breaking
                                   M 
(Arkani-Hamed, Kaplan, HM, Nomura)  1  d 4 q (LH u N )
                                Erice 2005   Pl          22
                 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!



                              Erice 2005   23
           Seesaw Mechanism

• Why is neutrino mass so small?
• Need right-handed neutrinos to generate
  neutrino mass , but nR SM neutral
                            mD   n L          2
        n L   n R                     mn 
                                                 mD
                                                     mD
                     mD     M  n R           M


To obtain m3~(Dm2atm)1/2, mD~mt, M3~1015GeV (GUT!)
                           Erice 2005                  24
             Grand Unification
                                                        M3
• electromagnetic, weak, and
  strong forces have very
  different strengths
• But their strengths become the
  same at 1016 GeV if
  supersymmetry
• To obtain
  m3~(Dm2atm)1/2, mD~mt
                                       Neutrino mass may be
        M3~1015GeV!
                                        probing unification:
                                         Einstein’s dream
                          Erice 2005                         25
Seven Questions
  Three-generation Framework

• Standard parameterization of MNS matrix
  for 3 generations
             U e1 U e 2 U e 3 
                              
    U MNS  U m1 U m 2 U m 3 
                              
             Ut 1 Ut 2 Ut 3 
      1             c13         s13ei  c12 s12 
                                                   
         c 23 s23            1          s12 c12 
                        i                         
       s23 c 23 s13e            c13             1

      atmospheric              ???            solar
                            Erice 2005                      27
                 Three-generation
• Solar, reactor, atmospheric and
  K2K data easily accommodated
  within three generations
• sin22q23 near maximal
  Dm2atm ~ 2.510–3eV2
• sin22q12 large
  Dm2solar ~810–5eV2
• sin22q13=|Ue3|2< 0.05 from
  CHOOZ, Palo Verde
• Because of small sin22q13, solar
  (reactor) & atmospheric n
  oscillations almost decouple
                                             Maltoni et al, hep-ph/0405172


                                Erice 2005                             28
               Six
              Seven Questions
•   Dirac or Majorana?
•   Absolute mass scale?
•   How small is q13?
•   CP Violation?
•   Mass hierarchy?
•   Verify Oscillation?
•   LSND? Sterile neutrino(s)? CPT violation?


                        Erice 2005              29
       KamLAND oscillation

• Now strong evidence that neutrinos do
  disappear and reappear (and again)



                                 Oscillation!



                   Erice 2005             30
Neutrinoless Double-beta Decay
• The only known practical
  approach to discriminate
  Majorana vs Dirac
  neutrinos
  0nbb: nn  ppe–e– with
  no neutrinos
• Matrix element 
  <mne>=SimniUei2
• Current limit
  |<mne>| ≤ about 1eV

                         Erice 2005   31
  Three Types of Mass Spectrum
• Degenerate
   –   All three around >0.1eV with small splittings
   –   Laboratory limit: m<2.3eV
   –   May be confirmed by KATRIN, cosmology
   –   |<mne>|=|SimniUei2|>m cos22q12>0.07m
• Inverted
   – m3~0, m1~m2~(Dm223)1/2≈0.05eV
   – May be confirmed by long-baseline experiment with matter effect
   – |<mne>|=|SimniUei2|>(Dm223)1/2 cos22q12>0.013eV (HM, Peña-Garay)
• Normal
   – m1~m2~0, m3~(Dm223)1/2≈0.05eV
   – |<mne>|=|SimniUei2| may be zero even if Majorana
                                Erice 2005                          32
           Cosmological Limit
• CMB+LSS+Lyman a (Seljak et al, astro-ph/0407372) :
  Si mni<0.42 eV, mn1<0.13 eV (95% CL)
• Puts upper limit on the effective neutrino
  mass in the neutrinoless double beta decay
  (Pierce, HM)
   – |<mne>|=|SimniUei2|<Simni |Uei2|<0.13eV
   – Heidelberg-Moscow: |<mne>|=0.11–0.56 eV
   – Reanalysis with Vogel’s MEs: |<mne>|=0.4–1.3 eV

                         Erice 2005                    33
       Cosmology vs Laboratory
• Global fit to the “World
  Data”
• indeed, tension between
  the Heidelberg-Moscow
  claim and cosmology
• Still subject to the
  uncertainties in nuclear
  matrix element (Bahcall, HM,
  Peña-Garay)
• Better data and theory
  needed!
                                         Lisi et al, hep-ph/0408045
                            Erice 2005                                34
      Why do we exist?
Matter Anti-matter Asymmetry
Erice 2005   36
Matter and Anti-Matter
   Early Universe


10,000,000,001                10,000,000,000




    Matter                      Anti-matter



                 Erice 2005                    37
Matter and Anti-Matter
  Current Universe
            us

            1




   Matter                    Anti-matter
      The Great Annihilation


                Erice 2005                 38
                      Baryogenesis
•   Gaussian scale-invariant fluctuation  inflation
•   Initial condition wiped out
•   What created this tiny excess matter?
•   Necessary conditions for baryogenesis (Sakharov):
    – Baryon number non-conservation
    – CP violation
        (subtle difference between matter and anti-matter)
    – Non-equilibrium
       G(DB>0) > G(DB<0)
• It looks like neutrinos have no role in this…


                                  Erice 2005                 39
         Electroweak Anomaly
• Actually, SM converts
  L (n) to B (quarks).
                                            QuickTime™ an d a
                                               decompressor
                                      are need ed to see this picture.




  – In Early Universe (T >
    200GeV), W is
    massless and fluctuate
    in W plasma
  – Energy levels for left-
    handed quarks/leptons                   QuickTime™ an d a
                                               decompressor
                                      are need ed to see this picture.


    fluctuate correspon-
    dingly

DL=DQ=DQ=DQ=DB=1  DB–L)=0
                         Erice 2005                                      40
                   Leptogenesis
• You generate Lepton Asymmetry first. (Fukugita, Yanagida)
• Generate L from the direct CP violation in right-handed
  neutrino decay



                                                  * *
     G(N1  n i H)  G(N1  n i H)  Im( h1j h1k hlk hlj )
• 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)                  41
                                               ~
                                               nR

    Origin of Universe
                                                                             QuickTime™ an d a
                                                                           Cinepak decompressor
                                                                       are need ed to see this picture.




• Maybe an even bigger role: inflation
• Need a spinless field that
     – slowly rolls down the potential




                                                amplitude
     – oscillates around it minimum                                          QuickTime™ an d a
     – decays to produce a thermal bath                                    Cinepak decompressor
                                                                       are need ed to see this picture.
• The superpartner of right-handed
  neutrino fits the bill
• When it decays, it produces the

                                                size of the universe
  lepton asymmetry at the same time
    (HM, Suzuki, Yanagida, Yokoyama)
•   Decay products: supersymmetry and
    hence dark matter                                                        QuickTime™ an d a
                                                                           Cinepak decompressor
Neutrino is mother of the Universe?                                    are need ed to see this picture.




                                       Erice 2005                                                         42
        Origin of the Universe
• Right-handed scalar
  neutrino: V=m2f2
• ns=0.96
• r=0.16
• Detection possible in
  the near future




                          Erice 2005   43
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
  – 0nbb found
  – CP violation found in neutrino oscillation
  – EW baryogenesis ruled out
               Archeological evidences

                      Erice 2005                 44
Models of Flavor
             Question of Flavor
• What distinguishes different generations?
   – Same gauge quantum numbers, yet different
• Hierarchy with small mixings:
       Need some ordered structure
• Probably a hidden flavor quantum number
       Need flavor symmetry
   – Flavor symmetry must allow top Yukawa
   – Other Yukawas forbidden
   – Small symmetry breaking generates small Yukawas
• Repeat Gell-Mann Okubo!
                             Erice 2005                46
            Broken Flavor Symmetry
   • Flavor quantum numbers (SU(5)-like):
      – 10(Q, uR, eR) (+2, +1, 0)
      – 5*(L, dR) (+1, +1, +1)
   • Flavor symmetry broken by a VEV ~0.02
      4    3
                  2        3        3
                                             3       3   2
                                                                    
      3                     2                       2           
Mu ~       2      , Md~       2        2
                                               , Ml~     2     
      2                                             3     2     
                1                                       
      – mu:mc:mt ~ md2:ms2:mb2 ~ me2:mm2:mt2 ~4: 2 :1
                            Erice 2005                         47
                Not bad!

• mb~ 3mt, ms ~ 3mm, md ~ 3me
• mu:mc:mt ~ md2:ms2:mb2 ~ me2:mm2:mt2




                    Erice 2005           48
    New Insight from Neutrinos

• Neutrinos are already providing significant
  new information about flavor symmetries
• If LMA, all mixing except Ue3 large
         big big medium n e    2
                             Dmsolar
e m t  big big  big n m 
                                    2    ~ 0.01 – 0.2
                   big  n t  Dmatm
                        
         big big
  – Two mass splittings not very different
  – Atmospheric mixing maximal
  – Any new symmetry or structure behind it?
                       Erice 2005                   49
      Is There a Structure
 in Neutrino Masses & Mixings?

• Monte Carlo random complex 33 matrices
  with seesaw mechanism
          (Hall, HM, Weiner; Haba, HM)




                    Erice 2005           50
                        Anarchy
 • Reasonable distributions from randomness
      Underlying symmetries don’t distinguish 3 neutrinos.
 • Flavor quantum numbers:
     – 10(Q, uR, eR) (+2, +1, 0)
     – 5*(L, dR) (+1, +1, +1)
       Inconceivable just a few years ago
       4  3  2        3  3  3   3  2            1 1 1
       3 2               2        2   2                       
M u ~                         2
                 , M d~    , M l~   2      , M n ~ 1 1 1
       2  1                      3  2                   
                                                       1 1 1

                             Erice 2005                          51
                  q13 in Anarchy
•   q13 cannot be too small if
    anarchy
•   How often can “large”
    angle fluctuate down to
    the CHOOZ limit?
•   Kolmogorov–Smirnov
    test: 12%
•   sin2 2q13>0.004 (3s)
•   CP violation likely
    observable at long
    baseline experiment

                              Erice 2005   (de Gouvêa, HM)   52
            Anarchy is Peaceful
• Anarchy (Miriam-Webster):
  “A utopian society of individuals who enjoy complete
  freedom without government”
• Peaceful ideology that neutrinos work together
  based on their good will
• Predicts large mixings, LMA, large CP violation
• sin22q13 just below the bound
• Ideal for superbeam, n-factory
   Pro-globalization!
                          Erice 2005                     53
Different Flavor Symmetries
    Altarelli-Feruglio-Masina hep-ph/0210342



                                               Hall, HM, Weiner
                                               Sato, Yanagida
                                               Vissani




                                               Barbieri et al


                    Erice 2005                          54
          Critical Measurements
• sin2 2q23=1.000.01?
   – Determines a need for a new symmetry to enforce the maximal
     mixing
• sin2 2q13<0.01?
   – Determines if the flavor quantum number of electron is different
     from mu, tau
• Normal or inverted hierarchy?
   – Most symmetries predict the normal hierarchy
• CP Violation?
   – Plausibility test of leptogenesis



                                Erice 2005                              55
                Large q23 and quarks
•   Large mixing between nt and nm
•   Make it SU(5) GUT
•   Then a large mixing between sR
    and bR
•   Mixing among right-handed fields
    drop out from CKM matrix
•   But mixing among superpartners
    physical
•   O(1) effects on bs transition
    possible
        (Chang, Masiero, HM)
•   Expect CP violation in neutrino
    sector especially if leptogenesis
•   BsJ/y f Bdf Ks


                                        Erice 2005   56
              More Fossils:
         Lepton Flavor Violation
• Neutrino oscillation
   lepton family number is not conserved!
   –   Any tests using charged leptons?
   –   Top quark unified with leptons
   –   Slepton masses split in up- or neutrino-basis
   –   Causes lepton-flavor violation (Barbieri, Hall)
   –   predict B(tmg), B(meg), me at interesting (or too-
       large) levels


                           Erice 2005                      57
              Dynamics behind
              flavor symmetry?
• Once flavor symmetry structure identified (e.g., Gell-Man–
  Okubo), what is dynamics? (e.g., QCD)
• Supersymmetry:
   –Anomalous U(1) gauge symmetry with
   Green-Schwarz mechanism
• Large Extra Dimensions:
   –Fat brane with physically separated left-
   and right-handed particles
• Technicolor:
   –New broken gauge symmetries at
                       Erice 2005                         58
   100TeV scale
                     Conclusions
• Revolutions in neutrino physics
• The solar neutrino problem solved!
• Small but finite neutrino mass:
   – Probes physics beyond the standard model
   – New insights into the origin of flavor
   – Interesting interplay between neutrinos and cosmos
• Neutrino mass may be responsible for our existence
• Neutrinos may even be the origin of the universe
• A lot more to learn in the next few years


                              Erice 2005                  59
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Erice 2005   61

								
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