L

1
L
The
imits
ets
S
D
N
olutions
peak about LSND
Anomaly
ew
eutrinos in
iscoveries
elphi
WIN05 20th International Workshop on Weak
Interactions and Neutrinos Delphi, Greece, June
6-11, 2005
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• THE FACTS

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Non Standard results
Standard results
Neutrino disappearance
Solar neutrino deficit 8 s effect
Atmospheric neutrino anomaly 14 s effect
Neutrino Oscillations
Homestake, SAGE, GALLEX, SK, SNO KamLAND
SK and K2K
sin2 ?13 lt 0.047

• ? m221 (7.3 - 9.1) 10-5 eV2
• sin2 ?12 (0.23 0.37)

? m231 (1.4 3.3) 10-3 eV2 sin2 2?23 gt
0.90
M. Maltoni et al., New J. Phys. 6122, 2004
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Standard results
No neutrino disappearance

• Bugey (?e ? ?e)
• L 15 m , 40 m, 95 m E? few MeV ? ?m2
  0.01 1 eV2
• CHOOZ and Palo Verde (?e ? ?e) for ?13 small
• L 1000 m E? few MeV ? ?m2 10-3 eV2
• CCFR (?? ? ??)
• L 0.715 km and 1.116 km (2 detectors)
• 40 GeV lt E? lt 230 GeV ? ?m2 10 100 eV2
• CDHS (?? ? ??)
• L 0.130 km and 0.835 km (2 detectors)
• E? GeV ? ?m2 1 100 eV2

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Standard results
No neutrino appearance

• NOMAD (?? ? ?e)
• L 0.635 km 1 GeV lt E? lt 100 GeV ? ?m2 1
  100 eV2
• KARMEN (?? ? ?e)
• L 17.6 m 16 MeV lt E? lt 50 MeV ? ?m2 0.1
  10 eV2

So far, so good! No short baseline neutrino
anomaly Neutrino anomalies explained by
oscillations between 3 neutrinos ? 2 independent
?m2
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Non-Standard result
Neutrino appearance

• LSND (?? ? ?e)
• L 30 m 20 MeV lt E? lt 52.8 MeV ? ?m2 1
  10 eV2
• It did see ?e appearance!

But ? m2atm ? msol ? ? m2LSND
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The LSND experiment
A. Aguilar et al., Phys. Rev. D64112007, 2001
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3.3 s effect
A. Aguilar et al., Phys. Rev. D64112007, 2001
G. Drexlin, Nucl.Phys.Proc.Suppl.118146-153,2003
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THE ESPECULATIONS
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Classifying solutions

• With and without sterile neutrinos
• With one and with more than one sterile
• With and without neutrino oscillations
• With and without CPT violation
• With non-standard and with standard processes
• With and without extra dimensions
• With problems and with problems
• Those we like and those we dont like
• Those we have proposed and those we havent
  proposed
• No solution

But if LSND is right, all imply NEW PHYSICS!
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4 neutrino models
22
31
?e ?? ?? ?s
? m2atm
? m2LSND
? m2LSND
? m2atm
? m2sol
? m2sol
Disfavored by SBL and atmospheric neutrino
experiments
Steriles would participate in solar and
atmospheric neutrino oscillations Ruled out at
5.1 s
M. Maltoni et al., New J. Phys. 6122, 2004
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32 neutrino models
? m2LSND2
? m2LSND1
? m2atm
? m2sol
Compatibility between SBL (including KARMEN) and
LSND of 30, instead of 3.6 in the standard 31
model
M. Sorel, J. M. Conrad and M. H. Shaevitz, Phys.
Rev. D66033009,2002
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CPT violating spectra
?e ?? ??
?m2atm
?m2sol
H. Murayama and T. Yanagida, Phys. Lett.
B520263-268, 2001 G.Barenboim, L. Borissov and
J. Lykken, Phys.Lett.B534106-113,2002
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4 neutrinos CPT violation
Assuming the same ?m2 for neutrinos and
antineutrinos but different mixings

• 31 models
• - U? 4 constrained by CCFR and atmospherics,
  not CDHS ? still some room
• - Ue4 constrained by GALLEX
• (?e disappearance during test with a 51Cr
  source)
• 22 models
• Too little sterile content on solar and
• atmospheric neutrino oscillations ? Ruled out
• Hybrid models
• (31)? , (22)? no bound from solar neutrino
  data
• (31)? , (22)? similar to (22) ? excluded

V. Barger, D. Marfatia and K. Whisnant, Phys.
Lett. B576303-308,2003
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CPT violating decoherence
Quatum gravity models involve singular space-time
configurations space-time foam ? decoherence is
the result of particle propagation due to the
fuzzy properties of the background not
necessarily related to mass differences between
particles and antiparticles Simple model
effects only in the antineutrino sector and
diagonal decoherence matrix ? No spectral
distortions at KamLAND
Without KamLAND
With KamLAND
G. Barenboim and N. E. Mavromatos, JHEP01034,
2005
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Lorentz violation
In the minimal Standard Model Extension (SME)
with Lorentz violation, neutrinos are massless
and oscillations are determined by 102 real
constants controlling the Lorentz violation
V. A. Kostelecký and M. Mewes, Phys. Rev.
D69016005, 2004
P (?? ? ?e) ' (heff)?e2 L2 ? for LSND
(heff)?e2 (3 x 10-19 GeV)2
aL 10-19 GeV cL 10-17
V. A. Kostelecký and M. Mewes, Phys. Rev.
D70076002, 2004
Unusual dependences for the oscillation phases
aL L and cL L E Predict, e.g., azimuthal
dependence for atmospheric neutrinos Constraints
(in the ? - ? sector) aL lt few 10-23 GeV cL lt
10-24
M. C. González-García and M. Maltoni. Phys. Rev.
D70033010, 2004
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LFV muon decay
The ?L 2 decay ? ? e ?e ?? (? e, ?,
?) could explain LSND data if
K. S. Babu and S. Pakvasa, hep-ph/0204236
B. Armbruster et al., Phys. Rev. Lett. 90181804,
2004
Scale of new physics relatively low, ? 300-400
GeV, ? effects on low energy observables, e.g.,
the SM ? parameter in the Michel spectrum
Predicted ? 0.7485 TWIST experiment Measured
? 0.75080 0.00032 0.00097 0.00023
J. R. Musser et al., Phys. Rev. Lett. 94101805,
2005
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Mass varying neutrinos
Matter effects on neutrinos due to the
interaction with a very light and weakly coupled
scalar particle could give rise to masses and
mixings which are enviroment dependent
Yukawa couplings
Nucleon number density
V(?)

• LSND, KamLAND, K2K and Palo Verde are
• in matter
• Bugey and CHOOZ are in air
• KARMEN is 50 in matter and 50 in air
• CDHS is unknown
• It could accomodate 31 models an experiment
• like Bugey but in matter should see
  disappearance
• Limits for 22 models are very model dependent

D. B. Kaplan, A. E. Nelson and N. Weiner, Phys.
Rev. Lett. 93091801, 2004 K. M. Zurek, JHEP
0410058, 2004
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Shortcuts in extra dimesions
In some theories with extra dimensions, SM
particles propagate only in the brane, but non-SM
particles can also do it in the bulk. If the
brane is distorted ? shortcuts
?s travel faster
This induces an effective term in the hamiltonian
which introduces resonant mixing driven by ?, the
aspect ratio of the brane deformation
The key point evading CDHS bounds by a resonance
in the range 30 - 400 MeV
No effect
No bound
If Eres 30 100 MeV ? no
signal in MiniBooNE If Eres 200 400 MeV ?
impressive signature in MiniBooNE
H. Päs, S. Pakvasa and T. J. Weiler hep-ph/0504096
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Neutrino oscillations decay
The decay option key ingredient to evade CDHS
bounds For small U?4 and short baselines
CDHS compares measurements at two detectors if
D1 D2 , no difference
This requires ?4 / m4 0.03-0.1 and m4 few eV
? g 103 -104 In contradiction with laboratory
bounds g lt 10-2
E. Ma, G. Rajasekaran and I. Stancu, Phys. Rev.
D61071302, 2000
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Neutrino decay
31 model with a decay option but LSND
explained by decay
Good fit to data
SPR, S. Pascoli and T. Schwetz, hep-ph/0505216
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LSND and KARMEN compatibility
Mixing of ?e with ?4 is not required ? we set Ue4
0 Only CDHS and atmospherics constrain the
model
SPR, S. Pascoli and T. Schwetz, hep-ph/0505216
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The rate of Ns is controlled by U? 4 and that of
?es by ghe In order to be consistent with
laboratory and supernova bounds, a typical value
is g 10-5 With ?-1 LLSND (g m4 1 - 10
eV) ? m4 100 keV
In addition, extending the model with an extra
neutrino and allowing for complex couplings, the
signal in the neutrino run might be suppressed
The MiniBooNE signal
SPR, S. Pascoli and T. Schwetz, hep-ph/0505216
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• THE RIGHT ONE

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• ??

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Conclusions

• Solar (8s) and atmospheric neutrino (14s)
  anomalies well understood in terms of
  oscillations
• LSND the only (anti)neutrino appearance
  experiment with positive signal (3.3s) why
  shouldnt it be right?
• Many possible solutions
• if LSND is right, (hopefully) one must be right
• If so, we might need to forget about our
  prejudices on sacred principles, modify the
  Standard Model of Cosmology
• We all will have more fun!
• If anyone is in a hurry

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we could ask to Delphis Oracle
Oracular responses were given every month, on the
7th day, the birthday of Apollo
Unfortunately

• So we will wait for MiniBooNE!