Neutrino Physics

1
Neutrino Physics

• Hitoshi Murayama (BerkeleyIPMU)
• NNN 2007, Hamamatsu
• Oct 3, 2007

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Outline

• Past Why Neutrinos?
• Present Era of Revolution
• Near Future Bright Prospect
• Big Questions Need Synergies
• Astrophysical Probe
• Conclusion

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Past

• Why Neutrinos?

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Probe to High Energies

• Effects of physics beyond the SM as effective
  operators
• Can be classified systematically (Weinberg)

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Unique Role of Neutrino Mass

• Lowest order effect of physics at short distances
• Tiny effect (mn/En)2(0.1eV/GeV)21020!
• 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
• Not entirely surprising (in retrospect) that
  neutrino mass was the first evidence for physics
  beyond standard model

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Ubiquitous Neutrinos
They must have played some important role in the
universe!
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Astrophysical Probe

• Neutrinos unhindered by the entire star, dusts,
  CMB, galactic intergalactic B, even last
  rescattering surface
• Possible probe into
• Core of stars (Sun, supernovae, GRB)
• Near blackholes (AGN)
• Dark Matter (Sun, galactic center, subhalo)
• Cosmology?

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Present

• Era of Revolution

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The Data

• Evidence for oscillation
• Indisputable
• Atmospheric
• Solar
• Reactor
• strong
• Accelerator (K2K)
• And we shouldnt forget
• unconfirmed
• Accelerator (LSND)

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SuperKamiokande Atmospheric ? disappear
Downwards ??s dont disappear
1/2 of upwards ??s do disappear
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SNOSolar ? transform in flavor
2/3 of ?es ? ????
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KamLANDReactor neutrinos do oscillate!
?Proper time ?
L0180 km
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What we learned

• Lepton Flavor is not conserved
• Neutrinos have tiny mass, not very hierarchical
• Neutrinos mix a lot
• the first evidence for
• demise of the Minimal Standard Model
• Very different from quarks

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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

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Immediate Questions

• Dirac or Majorana?
• Absolute mass scale?
• How small is q13?
• CP Violation?
• Mass hierarchy?
• Is q23 maximal?

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Future

• Bright Prospect

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Immediate Questions

• Dirac or Majorana?
• Absolute mass scale?
• How small is q13?
• CP Violation?
• Mass hierarchy?
• Is q23 maximal?

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Extended Standard Model

• Massive Neutrinos ? Minimal SM incomplete
• How exactly do we extend it?
• Abandon either
• Minimality introduce new unobserved light
  degrees of freedom (right-handed neutrinos)
• Lepton number abandon distinction between
  neutrinos and anti-neutrinos and hence matter and
  anti-matter
• Dirac or Majorana neutrino
• Without knowing which, we dont know how to
  extend the Standard Model
• KATRIN, 0???, Large Scale Structure

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Immediate Questions

• Dirac or Majorana?
• Absolute mass scale?
• How small is q13?
• CP Violation?
• Mass hierarchy?
• Is q23 maximal?

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T2K (Tokai to Kamioka)
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Immediate Questions

• Dirac or Majorana?
• Absolute mass scale?
• How small is q13?
• CP Violation?
• Mass hierarchy?
• Is q23 maximal?
• LSND? Sterile neutrino(s)? CPT violation?

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LMA confirmed by KamLAND

• Dream case for neutrino oscillation physics!
• Dm2solar within reach of long-baseline expts
• Even CP violation may be probable
• Possible only if
• Dm122, s12 large enough (LMA)
• q13 large enough

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q13 decides the future

• The value of q13 crucial for the future of
  neutrino oscillation physics
• Determines the required facility/parameters/baseli
  ne/energy
• sin22q13gt0.01 ? conventional neutrino beam
• sin22q13lt0.01 ? ? storage ring, ? beam
• Two paths to determine q13
• Long-baseline accelerator T2K, NO?A
• Reactor neutrino experiment 2?CHOOZ, Daya Bay

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NO?AFermilab to Minnesota
25kt
NOnA
MINOS
L810km
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Daya Bay
Empty detectors moved to underground halls
through access tunnel. Filled detectors swapped
between underground halls via horizontal tunnels.
Ling Ao Near 500 m from Ling Ao Overburden 98 m
Ling Ao-ll NPP (under const.)
Ling Ao NPP
Entrance portal
Daya Bay NPP
Total tunnel length 2700 m
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3? sensitivity on sin2 2?13
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T2K vs NO?A

• LBL ????e appearance
• Combination of
• sin22?13
• Matter effect
• CP phase ?

95CL resolutionof mass hierarchy
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Accelerator vs Reactor
Reactor w 100t (3 yrs) T2K T2K (5yr,n-only)
Reactor w 10t (3 yrs) T2K
90 CL
90 CL
Reactor experiments can help in Resolving the
?23 degeneracy (Example sin22?23 0.95
0.01)
Reactor w 100t (3 yrs) Nova Nova only (3yr
3yr) Reactor w 10t (3yrs) Nova
90 CL
McConnel Shaevitz, hep-ex/0409028
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My prejudice
?23
?12
?13

• Lets not write a complicated theory
• The only natural measure for mixing angles is the
  group-theoretical invariant Haar measure
• KolmogorovSmirnov test 64
• sin2 2q13gt0.04 (2s)
• sin2 2q13gt0.01 (99CL)

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T2KK
CP-violation may be observed in neutrino
oscillation!
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Big Questions

• Need Synergies

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Immediate Questions

• Dirac or Majorana?
• Absolute mass scale?
• How small is q13?
• CP Violation?
• Mass hierarchy?
• Is q23 maximal?

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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

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Seesaw Mechanism

• Why is neutrino mass so small?
• Need right-handed neutrinos to generate neutrino
  mass

, but nR SM neutral
To obtain m3(Dm2atm)1/2, mDmt, M310141015 GeV
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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)

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Origin of Universe
V(?)

• Maybe an even bigger role
• Microscopically small Universe at Big Bang got
  stretched by an exponential expansion (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)
• Neutrino is mother of the Universe?

?
log R
t
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LHC/ILC may help

• LHC finds SUSY
• ILC measures masses precisely

• If both gaugino and sfermion masses unify, there
  cant be new particles lt 1014GeV except for
  gauge-singlets

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Plausible scenario

• 0??? found
• LHC discovers SUSY
• ILC shows unification of gaugino and scalar
  masses
• Dark matter concordance between collider,
  cosmology, direct detection
• CP in ?-oscillation found

• Lepton flavor violation limits (??e?, ??e
  conversion, ???? etc) improve or discovered
• Tevatron and EDM (e and n) exclude Electroweak
  Baryogenesis
• CMB B-mode polarization gives tensor mode r0.16

If this happens, we will be led to
believe seesawleptogenesis (Buckley, HM)
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Neutrinos as Astrophysical Probe
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Dark Matter

• Indirect detection of galactic dark matter
• From the Sun, Galactic Center, Subhalos

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??s ??s

• EGRET down to ??2?10-8cm-2sec-1
• GLAST down to ??10-11cm-2sec-1
• Neutrinos/km3 ??4?10-10cm-2sec-1
• The catch
• GLASTgtGeV
• Icecubegt100GeV?
• Cross-correlation between ??s ??s gives us
  understanding of the source

Buckley, Freese, HM, Spolyar, Sourav
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Dark Energy with Neutrinos?

• Supernova relic neutrinos come from cosmological
  distances
• Its spectrum redshifted and superimposed
• Depends not only supernova rates and spectra, but
  also on the geometry of space
• Count Type-II_at_SNAP

• In principle, sensitive to Dark Energy
• HyperGADZOOKS!

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Conclusions

• Neutrino oscillation a unique tool to probe
  (very) high-energy world
• Era of revolution
• sin2 2?13 decides the future of LBL expts
• My prejudice ?13 is large
• Reactor accelerator LBL expts complementary
• To understand big questions we need a diverse
  set of experiments
• Neutrinos are also unique astrophysical probes