most pressing questions
DESCRIPTION
Why 3 neutrinos? Normal or inverted hierarchy? CP violation? (after q 13 ) Nature of the neutrinos, Dirac or Majorana? Magnetic moment/radiative decays? Right-handed (sterile) neutrinos? VHE neutrinos? What about Big Bang neutrinos?. Most pressing questions. CP violation. - PowerPoint PPT PresentationTRANSCRIPT
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Most pressing questions
Why 3 neutrinos?
Normal or inverted hierarchy?
CP violation? (after 13)
Nature of the neutrinos, Dirac or Majorana?
Magnetic moment/radiative decays?
Right-handed (sterile) neutrinos?
VHE neutrinos?
What about Big Bang neutrinos?
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CP violation
)()( ee PP
13 is crucial to test CP violationIf leptonic CP violation is observed, leptogenesis can trigger baryogenesis
)()( ee PP
)4
sin(4
)4
cos(~
)4
(sin2sin
)4
(sin2sin)(
ceInterferen
213
212
213
Solar
2122
1222
23
cAtmospheri
2132
1322
23
E
Lm
E
Lm
E
LmJ
E
Lmc
E
LmsP e
J~cos13 sin213sin223 sin212sin
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Super beams, beta beams, factories
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New detectors
LAGUNA study for Large scale underground laboratory (1’000’000 m3)
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Dirac or Majorana neutrinos
• Complexity of the neutrino nature– LH gives LH e-
– RH anti- gives RH e+
• Mass term in Lagrangian mixes RH and LH terms
• Two possibilities:– existence of a R (Dirac neutrino)
– or association of and anti- (Majorana neutrino)
• Identical consequences if 0 mass
• Is the its own antiparticle?
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Double decays• With or without neutrino, this is the question !
With neutrinos, already seenWithout neutrinos, 2 e- carry all available energy
Extremely rare!
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Detectors
Two techniques:
Calorimeters (Ge) or spectrometers
Heidelberg-Moscow Nemo3
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Present limits
Level reached ~ 1 eVNext generation ~ 0.1 eV
m = U2 mi
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Correlations
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Right-handed (Sterile) neutrinos
• See-saw formula for active neutrinos m=MD(1/MM)(MD)T
– Majorana mass MM – Dirac mass MD=fv v=174 GeV vac. exp. val. of Higgs field
New model : MSM f small, N1 (10 keV), N2, N3 (100 MeV-1 GeV)
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Limits
A massless detector for massive neutrinos (1984)
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E.M. interactions of neutrinos
1) Magnetic moment
(e) < 10-11B (theory 10-19B for 1 eV mass)
2) Radiative decays
• Mass hierarchy E = E/2
• SN anti-e /m > 6 1015 s/eV
• Los Alamos /m > 15,4 s/eV
• Degenerated masses E = E m2/m2 = 2 E m/m
• Bugey anti-e /m > 2 10-4 s/eV if m/m > 10-7
• Solar eclipse /m > 100 s/eV if m2 ~ 10-5 eV2
3) Stimulated conversion
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Neutrino astronomy
Up to now, only two sources seen in the sky:
- The Sun and the supernova 1987A
Towards a neutrino sky map
Astroparticles « par excellence », protons feel magnetic fields and GZK mechanism. Photons interact with I.R. backgroundOnly neutrinos can reach from the frontiers of the Universe, but weak cross-sections mean huge detectors
p
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Predictions?
• Presumably protons are accelerated in SN remnants (1015 eV)• Also in jets, in particular in AGN (1018 eV)• On their way, protons interact giving 0 and ±.
• Sure contribution: from GZK suppression p + n
• At production, 2 for 1 e
• On earth, after oscillations, equal fluxes of e, ,
• Detectors 10000 bigger than SuperK are necessary.• Only possible in instrumenting existing media: Antarctic ice or
sea(lake) water.
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VHE neutrino detection
• Small fluxes but cross-section increases (although not linear anymore)
neutrino
Muon or tau
Generated ou can cross large distances in matter: few km for in rock, up to 30 km for Catastrophic bremsstrahlungCatastrophic bremsstrahlung
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At the South pole
• Cables with photomultiplier tubes are lowered in deep holes excavated in ice.
• Detection technique again based on light produced by Cerenkov effect.
• AmandaB has already given results– volume 500 m high by100 m section.
• Icecube in construction. • Already 59/80 strings holding 60 PMs• Will be 1 km3 big• Such an apparatus observes the Northern hemisphere
because cosmic muon background is enormous.
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Existing limits
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IceCube
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In the Mediterranean sea
• Antarès uses sea water as target. Advantage: less diffusion, better angular resolution
• Cables anchored 2,5 km deep, 30 storeys of 3 PMs spaced15m.
• 12 lines are operational• 350m high with section 100m x 100m • Complementarity to Amanda/Icecube: • Antarès will observe the Southern hemisphere
(galactic center).• Towards a km3 detector in the Meditteranean sea.
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Antarès
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Completed May 2008
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Still beyond?
• Large volumes, but statistics very limited.• Efficient detection of muons and taus of VHE
Energy measurement and angular information OK• But earth is opaque above1014 eV• Auger or JEM-EUSO allow the search of
skimming neutrinos from 1018 eV to 1020 eV.• Other techniques are investigated: radio emission
or sound.• Radio detection already attempted: Rice at South
Pole (moon shadow). Coming, Anita, Codalema…
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Big bang neutrinos
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ConclusionsVery rich domain of physics. Important progresses recently achieved: neutrinos have masses
m() = 50 meV, m() = 9 meV, m(e) = ?
They represent 0,5% of the energy content of the Universe.
Large experimental program still ahead
Solution to the matter-antimatter asymetry?
Solution to the missing mass problem?
Solution to the dark energy problem?
Future will tell.
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The most incomprehensible of our story is that the Universe is comprehensible.
A. Einstein