Modeles Theoriques

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Modeles Theoriques

• Andrea Romanino
• CERN

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Plan of the talk

• Interpretation of ATM and SUN data
• Expectations for and
• Precise predictions for and

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Experimental constraints
(ATM, K2K) (SUN, KamLAND) (CHOOZ, Palo
Verde) (Heidelberg-Moscow) (Mainz,
Troitsk) (Cosmology)
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Smallness of neutrino masses

• Natural scale of fermion masses v 174 GeV
• Why
• (must have a different origin than

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Right-handed neutrinos
SO(10)
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See-saw
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Origin of large mixings
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• (from in the case of degenerate neutrinos)
• from in the case of normal hierarchy
• from in the case of inverse hierarchy
• from
• (anarchy)

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Large angles?

• Dirac and Majorana
  mass terms trasform differently under symmetries
• E.g. . In the symmetric limit
• However, it only works
• with degenerate ?s
• E.g.
• Requires a non abelian symmetry acting on the
  three families
• Often unstable

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• However A, B are not fundamental parameters
• see-saw
• Natural solution

King
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e.g. Altarelli Feruglio and refs
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• Inverse Hierarchy barring tunings or
  cancellations, must be close to the
  experimental limit
• In fact
• an inverse hierarchy requires, barring tunings, a
  correction to from
• a correction to from contributes to

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• Correction from
• Correction from

• an inverse hierarchy requires, barring tunings, a
  correction to from

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• a correction to from contributes to

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• In all cases, contributes to
• is also model-dependent, but involves the
  charged fermions
• Implementing the same pattern in (e.g.
  SU(5))
• Central value observable with suberbeams (but gt
  O(1) uncertainty)

Gatto Sartori
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Feruglio Strumia Vissani
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Minimal models

• Use the minimal number of effective parameters
  needed to account for the data 41
• Produce 2 correlations among
• i.e. a prediction for

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Reducing the number of parameters

• Simplest possibility assume the presence of (2)
  zeros in the neutrino mass matrix written in the
  flavor basis,
• However, the parameters in are only
  combinations of the parameters in the basic
  lagrangian
• Our approach
• assume the relative smallness (vanishing) of some
  parameters in the basic lagrangian
• assume there are no correlations among those
  parameters (non-abelian symmetries could give
  rise to further possibilities)
• We find only 5 possible predictions

Frampton, Glashow, Marfatia
Barbieri, Hambye, AR
e.g. Ibarra, Ross
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Barbieri, Hambye, AR
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E is the only case which corresponds to IH and in
which the predictions depend on d (hence the
lower limit and the constraint cos d gt 0.8) In
case D, (hence the upper
limit) Cases A, B, E are within the sensitivity
of superbeams case C requires SB BB case D
has chances with a nu-factory. Cases A, B, C, D
assume no 12 rotation in the charged lepton
sector There are good prospects for 0?2ß decay
only in the IH case (E), but as long as d is not
known, there is no special prediction. Case A has
been first studied by Frampton, Glashow, Yanagida.
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Summary

• The present data can be comfortably accommodated
  in the standard framework for the origin of
  neutrino masses and provides valuable information
  on the structure of the basic lagrangian
• Based on the interpretation of present data, on
  our understanding of the charged fermion sector,
  and on naturalness considerations, there are good
  prospects of measuring with superbeams
• Despite the large number of model building
  possibilities, there is a relatively small number
  of possible predictions for compatible with
  not having correlations among the parameters in
  the basic lagrangian