Neutrino oscillations and non-standard neutrino-matter interactions (NSI)

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Neutrino oscillations and non-standard
neutrino-matter interactions (NSI)

• Cecilia Lunardini
• INT UW department of Physics, Seattle

• A.Friedland, C.L. M.Maltoni, PRD 70111301,
  2004 (atmospheric n.),
• Friedland, C.L. Carlos Pena-Garay,
  Phys.Lett.B594347,2004 (solar n.) A. Friedland,
  C.L., to appear soon

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Contents

• Neutrino oscillations and matter effects
• Non standard interactions (NSI)?
• Testing NSI with oscillation experiments
• Atmospheric neutrinos

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Neutrino oscillations and matter effects
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Atmospheric neutrinos as probes of neutrino
interactions
From M.C. Gonzalez Garcia and Y. Nir,
Rev.Mod.Phys.75345-402,2003
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Event rates at SuperKamiokande
From M.C. Gonzalez Garcia and Y. Nir,
Rev.Mod.Phys.75345-402,2003
vacuum
matter
21/2 GF ne
D m2/4E
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Zenith distribution

• ne, unsuppressed -gt small ne mixing (q13, bound
  from reactors)
• nm has zenith-dependence suppression -gt large nm
  - nt mixing

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Results q p/4 , D m2 2.1 10-3 eV2
From M.C. Gonzalez Garcia and Y. Nir,
Rev.Mod.Phys.75345-402,2003
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The Hamiltonian 2 2 effective vacuum
ne,nm,nt basis
Small corrections due to solar mass splitting (D
m2sol 8 10-5 eV2) and mixing, and to q13
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Non standard interactions?

• Effects of (neutral current) NSI on neutrino
  oscillations

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New interactions (NSI)

• Predicted by physics beyond the standard model
• Can be flavor-preserving or flavor violating
• How large NSI ?
• Theory most likely small, but large values
  not impossible
• Experiments poor direct bounds from neutrinos
  (strong bounds from charged leptons not directly
  applicable because SU(2) is violated)

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• The Lagrangian

vertex Current bound
ee Pt tlt0.5 LEP
ed Pte lt1.6 CHARM
-0.4 lteu Ree lt 0.7 CHARM
FromS.Davidson, C.Pena-Garay and N.Rius, JHEP
0303011,2003
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Phenomenological approach

• We want to test NSI in a 3-flavor context, with
  NSI in e,t sector
• The oscillation Hamiltonian

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Important differences

• If eet¹ 0, Hmat is NOT flavor diagonal -gt
  conversion in the matter-dominated regime (high
  E)
• If et t¹ 0, nm -nt oscillations are
  matter-affected -gt suppression of mixing in the
  matter-dominated regime
• ne is coupled (mixed) to nm - nt by interplay of
  ee t and q

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Testing NSI with oscillation experiments
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What do we learn from atmospheric neutrinos?

• What is the region of NSI allowed by the data?
• Is this region interesting? More restricted than
  existing limits?
• If NSI are there, maybe the values of D m2
  and q are different from what we think?
• Fully general analysis (3-neutrinos)?

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Predicting the fit to data

• Consider the Hamiltonian in the matter
  eigenbasis (n2cosb ne sin b ei 2y nt, )
• l2,l1 matter eigenvalues , D ºD m232/(4E)

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1.Small NSI should be OK

• If l1 , l2 ltlt D, (-gt b 0) , the standard
  case is recovered

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2. Large NSI generally bad

• If l1, l2 gtgt D, nm oscillations are
  suppressed at high energy -gtincompatible with data

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3. With an exception!

• If l2 gtgt D, AND l1 ltlt D , nm oscillations
  are NOT suppressed at high energy nm
  n1 oscillations.
• Suppression reduction to 2 neutrinos

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Why does this work?

• Right nm disappearance at high energy (E 5 -100
  GeV)
• Similar to standard at lower energy (vacuum terms
  dominate)

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The c2 test

• Parameters D m2,q,eee, eet, ,et t per electron
  
• Data K2K (accelerator) 1489 days
  SuperKamiokande-I , 55 d.o.f.
• m , e contained
• Stopping and through going muons
• New 3D fluxes by Honda et al. (astro-ph/0404457)

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A smile
l10.2 (standard)
l10 (et te2et/(1eee))
l1-0.2 (standard)

• Section of 3D region at eee-0.15 (others
  marginalized) inverted hierarchy
• c2min48.50 for no NSI
• Contours c2 - c2min7.81,
  11.35, 18.80 (95,99, 3.6 s)

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And a butterfly

• Section of 3D region at eee-1
• Transition to case l2 ltlt D, AND l1 gtgt D

1
ett
-1
-0.4
0.4
eet
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K2K crucial!
Atmospheric only

• K2K matter-free
• Consistency K2K/atmospheric q qm p/4
  cos b gt 0.47

Atmospheric K2K
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Mass and mixing may change with NSI

• Shaded marginalized over NSI
• eee-0.15
• eet0,ett0, eet0.30,ett0.106
  eet0.60,ett0.424 eet0.9,ett0.953

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Taking into account NSI

• Mixing in matter maximal (qeff p/4) -gt smaller
  vacuum mixing q lt p/4
• Oscillation length in matter (zenith dependence)
  require D m2eff 2.2 10-3 eV -gt larger D m2
  D m2 2.6 - 2.8 10-3 eV

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q13 makes an asymmetric smile
eee0, sin q130.141
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Comments open issues

• Surprise! Atmospheric neutrinos allow large NSI
  in the e-t sector (NOT in the nm - nt sector)
• zeroth order effects are (surprisingly!) well
  predicted by analytics
• Subdominant effects calculable (in part) q13,
  solar parameters, emt, 3-neutrino effects,

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• What NSI are compatible with everything?
• Combine with solar neutrinos? Smile becomes
  restricted and asymmetric large NSI still
  allowed (work in progress)
• How to test the e-t NSI?
• Minos, LBL experiments, supernovae

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Conclusions

• Neutrino oscillations experiments put competitive
  constraints on NSI
• Atmospheric neutrinos allow large NSI in the e -
  t sector, along the parabolic direction l2 gtgt
  D, AND l1 ltlt D (l2 ltlt D, AND
  l1 gtgt D)
• NSI at the allowed level can change the vacuum
  parameters extracted from the data by (at least)
  few 10.
• They can be tested with neutrino beams
  (intermediate and long base lines)

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Solar neutrinos a new solution!

• LMA-0 Day/Night suppressed by (q - a)' 0.15
• eu11ed11-0.065 eu12 ed12-0.15

90,95,99,99.73 C.L.