Eligio Lisi

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Rencontres de Moriond
March 2005
Eligio Lisi INFN, Bari, Italy
Special thanks to G.L. Fogli, A. Marrone, A.
Melchiorri, A. Mirizzi, D. Montanino, A.M.
Rotunno, A. Palazzo
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Outline Overview of
3? mass-mixing parameters Constraints from ?
oscillation searches Constraints from
non-oscillation searches Combining oscill.
non-oscill. ? observables Beyond the standard
3? scenario (LSND) Conclusions

• Organizers request Talk should be a short
  introduction aimed
• at PhD students in experimental (non-neutrino)
  particle physics
• ? I shall skip all refs. or details for ?
  experts/theorists, with
• apologies to colleagues (for more info, see
  Proceedings or ask me)

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3? mixing
? Neutrinos mix (as quarks do)
? The standard rotation ordering of the CKM
matrix for quarks happens to be useful also
for neutrinos
but with very different angles
? Only if s213?0 one can hope to probe the
CP-violating phase ? (holy grail of future ?
oscillation experiments ? see Kaysers talk)
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3? mass2 spectrum and flavor content (e ? ?)
Absolute mass scale ? unknown but lt O(eV)
Hierarchy sign(?m2) unknown
?e content of ?3 unknown but lt few
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3? oscillations
Flavor is not conserved as
neutrinos propagate
Oscill. phase
Two macroscopic oscillation lengths governed by
?m2 and ?m2, with amplitudes governed by ?ij.
Leading expt. sensitivities
Atmospheric ?, K2K long baseline accelerator (a)
Solar ?, KamLAND long baseline reactor ? (b)
CHOOZ short-baseline reactor ? (a,b)
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Constraints on (?m2, ?23, ?13) from SK K2K
CHOOZ
See talks by Sulak (SK) and Mariani (K2K)
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Super-Kamiokande atmospheric ?
For ?130 and ?m20, a very simple formula fits
all SK data ( MACRO Soudan2)
1st oscillation dip still visible despite large L
E smearing
Strong constraints on the parameters (?m2,
?23)
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Atmospheric ? oscillation evidence robust
confirmed with lab-? in K2K Many interesting
details depend on theoretical input subleading
effects
Contours at 1, 2, 3? (1 dof). Note linear scale
for ?m2 and sin2?23, with 2nd octant of ?23
unfolded
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At the ?m2 scale of SKK2K, nonobservation of
?e??e in the CHOOZ reactor experiment sets
strong upper bounds on ?13
Growing literature interest in subleading
effects due to ?13, ?m2, sign(?m2), ? But need
very significant error reduction to probe them A
challenge for future high-statistics experiments
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Constraints on (?m2, ?12, ?13) from solar ?
KamLAND
See talks by Sulak (SK), Berger (kamLAND),
Miknaitis (new SNO data)
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Solar ?e??e,?,? vs atmospheric ????? matter
(MSW) effect
??,?
??,?

• Atmospheric ?? and ?? feel background
• fermions in the same way (through NC)
• no relative phase change ( vacuum-like)

Z
fermion
?e
?e
But ?e , in addition to NC, have CC interac. with
background electrons (density Ne). Energy
difference V ?2 GF Ne
W
e
e
Solar ? analysis must account for MSW effects in
the Sun and in the Earth (Earth matter
effects negligible for KamLAND reactor
neutrinos) SolarKamLAND combination provide
evidence for Vsun (not yet for Vearth)
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Dramatic reduction of the (?m2,?12) param. space
in 2001-2003 (note change of scales)
ClGaSK (2001) SNO-I
(2001-2002) KamLAND-I (2002)
SNO-II (2003)
( confirmation of solar model)
Direct proof of solar ?e???,? in SNO through
comparison of
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in 2004 (KamLAND-II with revised background)
unique Large Mixing Angle solution, and another
change of scale
evidence for oscillatory effects in KamLAND
reactor L/E spectrum
What about MSW effects?
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Exercise (1) Change MSW potential by hand, V
?aMSWV (2) Reanalyze all data with
(?m2,?12,aMSW) free (3) Project
(?m2,?12) away and check if aMSW1
( a way of measuring GF through solar
neutrino oscillations )
Results with 2004 data, aMSW1 confirmed within
factor of 2 and aMSW0 excluded ? Evidence for
MSW effects in the Sun But
expected subleading effect in the Earth
(day-night difference)
still below experimental uncertainties.
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2005 (last week) new data detailed analysis
from SNO
Solar
Previous results basically confirmed
Slightly higher ratio CC/NC P(?e??e)
SolarKL
Slight shift (lt1? upwards) of allowed range for
?12
2004
2005
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3? analysis of 2004 solarKamLAND data (?13 free)
Solar and KamLAND data also prefer ?130
(nontrivial consistency with SKCHOOZ)
Bounds on (?m2,?12) not significantly altered
for unconstrained ?13
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Grand Total from global analysis
of oscillation data
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Marginalized ??2 curves for each parameter (2004)
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Numerical 2? ranges (95 CL for 1dof), 2004 data
Note Precise values for ?12 and ?23 relevant for
model building (see talk by Tanimoto)
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Probing absolute ? masses through
non-oscillation searches
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Three main tools (m?, m??, ?)

• ? decay m2i ? 0 can affect spectrum endpoint.
  Sensitive to
• the effective electron neutrino mass
  (most direct method)

2) 0?2? decay Can occur if m2i ? 0 and ??.
Sensitive to the effective Majorana mass
(and phases) (several talks this afternoon)
3) Cosmology m2i ? 0 can affect large scale
structures in (standard) cosmology
constrained by CMBother data. Probes (see talk
by Pastor)
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Even without non-oscillation data, the (m?, m??,
?) parameter space is constrained by previous
oscillation results
Significant covariances
Partial overlap between the two hierarchies
Large m?? spread due to unknown Majorana phases
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But we do have information from non-oscillation
experiments

• ? decay no signal so far. Mainz Troitsk expts
  m? lt O(eV)

• 0?2? decay, no signal in all experiment, except
  in the most
• sensitive one (Heidelberg-Moscow). Rather
  debated claim.
• Claim accepted m?? in sub-eV range (with
  large uncertainties)
• Claim rejected m?? lt O(eV).

• Cosmology. Upper bounds
• ? lt eV/sub-eV range,
• depending on several
• inputs and priors. E.g.,

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0?2? claim rejected
0?2? claim accepted
Tension with cosmological bound (no
combination possible at face value) But too
early to draw definite conclusions
Cosmological bound dominates, but does not
probe hierarchy yet
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E.g., if 0?2? claim accepted cosmological
bounds relaxed
Combination of all data (oscnonosc.) possible
Complete overlap of the two hierarchies (degenerat
e spectrum with large masses)
High discovery potential in future (m?, m??, ?)
searches
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Beyond three-neutrino mixing LSND
Many theoretical reasons to go beyond the
standard 3? scenario A purely experimental
reason the puzzling LSND oscillation claim
?M2O(eV2) with very small mixing?
Solutions invented so far (new sterile states,
new interactions or properties) seem rather ad
hoc and/or in poor agreement with world
neutrino data
If MiniBoone (talk by McGregor) confirms LSND
this year, many ideas will be revised, and the
neutrino session of Moriond 2006 will be fun!
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Conclusions
Neutrino mass mixing established
fact Determination of (?m2,?12) and (?m2,?23)
Upper bounds on ?13 Oscillation-induced
spectral distortions Direct evidence for solar ?
flavor change Evidence for matter effects in the
Sun Upper bounds on ? masses in (sub)eV range
Great progress in recent years
Determination of ?13 Leptonic CP
violation Absolute m? from ?-decay and
cosmology Test of 0?2? claim and of
Dirac/Majorana ? Matter effects in the
Earth Normal vs inverted hierarchy Beyond the
standard 3? scenario Deeper theoretical
understanding
and great challenges for the future!