Neutrino Physics

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Neutrino Physics

• Oscillation (SK 1998 - MINOS 2006)
• Revolution (New parameters)
• Challenges and Tools (LBL)
• Implication (Particle Physics and Cosmology)

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• Oscillation

• Neutrino physics has surprised us all
• Many discoveries in the last 10 years
• Atmospheric ?? are converted to ?? (SK) (98)
• Solar ?e are converted to either ?? or ??(SNO)
  (02)
• Only the LMA solution left for solar neutrinos
  (HomestakeGalliumSKSNO) (02)
• Reactor anti-?e disappear/reappear (KamLAND) (04)
• Accelerator ?? disappear (K2K 04 , MINOS 06)
• MiniBoone fails to confirm LSND (07)

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(No Transcript)
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MiniBoone does not support the LSND result and
instead supports the three neutrino paradigm
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Neutrino oscillations quantum mechanics over
macroscopic distances

• Need coherent source
• Need interference (i.e., large mixing angles)
• Need long baseline

All provided by Nature
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MINOS Experiment
Chris Smith

• Main Injector Neutrino Oscillation Search
• High power nm beam produced by 120 GeV protons
  from the Main Injector at FNAL
• Two functionally identical detectors
• Near detector (ND) at Fermilab to measure the
  beam composition and energy spectrum
• Far detector (FD), 735km away, in the Soudan
  Mine, Minnesota to search for evidence of
  oscillations

735 km
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MINOS shifts up ? m232 a bit
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Latest global fit for atmospheric solar
oscillations

• Latest version Oct 07
• Latest SSM
• SNO salt data
• K2K
• Latest MINOS results

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• Revolution

• Lepton Flavor is not conserved
• Neutrinos have tiny masses, not very hierarchical
• Neutrinos mix a lot
• At least 7 new parameters for SM
• Quite unlike quark mass and mixing
• Of all fermions, neutrinos are least understood
• Tiny neutrino mass may indicate new physics

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7 New Parameters for SM!
3 masses 3 angles 1 phase 7 new parameters
for SM
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• Neutrino mass squared splittings and angles

3 ? errors
Valle et al
Normal
Inverted
Absolute neutrino mass scale?
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Tri-bimaximal mixing (TBM)
Harrison, Perkins, Scott
c.f. data

• Current data is consistent with TBM
• But no convincing reason for exact TBM expect
  deviations

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Useful to Parametrize lepton mixing matrix in
terms of deviations from tri-bimaximal mixing
SFK arXiv0710.0530 
r reactor
s solar
a atmospheric
Present data is consistent with r,s,a0
?tri-bimaximal
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c.f. Wolfenstein for quarks
Quark UT is very well determined
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In the case of leptons UT is unknown
Neither r nor ? is measured UT could be a
straight line!
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• The Challenges

• Measure the neutrino masses (m1, m2, m3 scale,
  ordering, nature)
• Measure the neutrino mixings (the
  deviations from tri-bimaximal mixing r,s,a and
  the CP phase ?)

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• The Tools

• Present experiments
• SuperK, KamLAND, Mini-BooNE, MINOS, Cuoricino,
  NEMO
• Forthcoming experiments
• CNGS, Double-Chooz Reactor, T2K, NO?A, KATRIN,
  0??? expts

• Possible future long baseline (LBL) experiments
• Superbeam upgrades, Beta beam or Neutrino Factory

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E.Falk
Daya Bay
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Oscillation formulae in terms of r,s,a
Only sensitive to the reactor parameter r
Reactor
L B L
Sensitive to r,s,a
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Oscillation formulae in terms of r,s,a (including
matter effects)
LBL
Sensitive to r, ?
For a list of formulae in terms of r,s,a see SFK
arXiv0710.0530 
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Future LBL Options

• Second generation super-beam CERN, FNAL, BNL,
  J-PARC II
• Neutrino Factory
• Beta-beam

Which one(s) to go for? ? ISS
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Prospects to measure ?13
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Prospects to measure CP Violation
ISS Scoping Study 06
Note choice of facility will depend on ?13
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Prospects to measure a s232- 0.5
S. Antusch, M. Huber, J. Kersten, T. Schwetz,
W. Winter
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Present 2 ? error
Prospects to measure the deviation of ?12 from
35o
SPMINreactor experiment at the first Survival
Probability Minimum
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• Implications for physics and cosmology

Particle Physics

• Origin of tiny neutrino mass
• Extra dimensions, See-saw mechanism, SUSY
• Unification of matter, forces and flavour
• GUTs, Family Symmetry, Strings,
• Did neutrinos play a role in our existence?
• Leptogenesis
• Did neutrinos play a role in forming galaxies?
• Hot/Warm Dark matter component
• Did neutrinos play a role in birth of the
  universe?
• Sneutrino inflation
• Can neutrinos shed light on dark energy? ? m?4

Cosmology
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• Neutrino mass is zero in the Standard Model for
  three reasons

• There are no right-handed neutrinos
• There are only Higgs doublets of SU(2)L
• There are only renormalizable terms

In the Standard Model these conditions all apply
so neutrinos are massless, with ?e , ?? , ??
distinguished by separate lepton numbers Le, L?,
L? Neutrinos and anti-neutrinos are distinguished
by the total conserved lepton number LLeL?L?
To generate neutrino mass we must relax 1 and/or
2 and/or 3
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Recall that a mass term can be thought of as an
interaction between left and right-handed chiral
fields
Left-handed neutrinos ?L can form masses with
either right-handed neutrinos ?R or with their
own CP conjugates ?cL
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Right-handed neutrinos ?R can also form masses
with their own CP conjugates ?Rc
Majorana
In principle there is nothing to prevent the
right-handed Majorana mass MRR from being
arbitrarily large since ?R is a gauge singlet
e.g. MRRMGUT On the other hand it is possible
that MRR 0 which could be enforced by lepton
number L conservation
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• Summary of Dirac vs. Majorana Mass

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• Dirac Neutrinos

Recall origin of electron mass in SM with
Yukawa coupling ?e must be small since ltH0gt175
GeV
Introduce right-handed neutrino ?eR with zero
Majorana mass
then Yukawa coupling generates a Dirac neutrino
mass
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• Q. Why are Dirac Yukawas so small? A.

Extra dimensions
An entomological analogy
Typical string/D-brane set-up involves extra
dimensions
bulk
brane
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• Flat extra dimensions with RH neutrinos in the
  bulk

Number of extra dimensions
e.g. for one extra dimension y the ?R
wavefunction spreads out over the extra
dimension, leading to a volume suppressed Yukawa
coupling at y0
?R in bulk
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• Warped extra dimensions with SM in the bulk

Overlap wavefunction of fermions with Higgs gives
exponentially suppressed Dirac masses, depending
on the fermion profiles
Planck brane
TeV brane
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• Majorana Neutrinos

Renormalisable ?L 2 operator
where ? is light Higgs triplet with VEV lt 8GeV
from ? parameter
Non-renormalisable ?L 2 operator
Weinberg
This is nice because it gives naturally small
Majorana neutrino masses mLL ltH0gt2/M where M is
some high energy scale The high mass scale can be
associated with some heavy particle of mass M
being exchanged (can be singlet or triplet)
e.g. see-saw mechanism at tree-level or singlet
Higgs exchange at one or two loops
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The See-Saw Mechanism
P.Minkowski, PLB67(1977)421
A very natural and appealing mechanism!
Neutrinos are so light because RH neutrino get
heavy Majorana masses (L number violated at HE)
Neutrinos are a probe of
physics at high energy scales up to MGUT!
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Sequential Dominance
SFK 98- (Basis Invariant 06)
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This implies a non-Abelian family symmetry
Need
with
2 3 symmetry (from maximal atmospheric
mixing) 1 2 3 symmetry (from tri-maximal solar
mixing)
Examples of suitable non-Abelian Family
Symmetries
SFK, Ross Velasco-Sevilla Varzelias
Discrete subgroups preferred by vacuum alignment
SFK, Malinsky
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Are neutrinos telling us something about
unification of matter, forces and flavour?
t
u
d
c
e
s
b
Family symmetry e.g. SU(3)
GUT symmetry e.g. SO(10)
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To build a model, must decide
Backup slides
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Survey of predictions for ?13 Albright and Chen
Large
Low
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Bjorken,Pakvasa,SFK
GUT Theory Prediction for ?13
.
.
.

.
Tri-bimaximal form for m?
. . .


GUT prediction for ?13
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SFK, Antusch,Masina
Sum Rule Prediction for ?12
Assume exact tri-bimaximal mixing in the neutrino
sector with Cabibbo-like charged lepton
corrections (motivated by GUTs) ? Sum rule
In the TBM parametrization recast as
CP phase
Solar
Reactor
Wolfenstein
Reactor
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Sum rule
Bands show 3 ? error for an optimized neutrino
factory determination of ?13cos ?
.
Current 3?
.
Antusch, Huber, SFK, Schwetz
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Prospects to measure sum rule combination ?13 cos
?
3? error in degrees on ?13cos ?
Antusch, Huber, SFK, Schwetz
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• Cosmology

WMAP 5 Year
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Temperature Maps
Earth
Universe
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• WMAP 5 shows that neutrinos must play an
  essential role in the Universe since n?n? gtgtne

Third peak provides evidence for the neutrino
cosmic background at 95 C.L.
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The Universe according to WMAP
Now
Then
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Did neutrinos play a role in forming galaxies?
Tegmark
Lesgourgues
CMB power spectrum
Galaxy power spectrum
Klapdor- signal 0.2 eV
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• Absolute ? mass scale and the nature of ? mass

Majorana (no signal if Dirac)
Neutrinoless double beta decay
Klapdor- 76 Ge 0.4 eV
(signal) Majorana 76 Ge 0.05
eV GERDA 76 Ge 0.1 eV (phase
II) 0.01
eV (phase III ) Non- 76 Ge CUORE, NEMO3
SuperNEMO ?50meV0.05 eV COBRA Cd116
??? EXO Xe136 1 ton 5y 50-70meV0.05-0.07eV SNO
Nd150 start 2011? ?50meV0.05 eV The
Future I 100-500meV SNemo CUORE GERDA EXO
SNO II 15-50meV 1 ton 10y? III 2-5meV 100 tons
20y??
Tritium beta decay
Present Mainz lt 2.2 eV KATRIN 0.35eV
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Cosmology vs Neutrinoless DBD
Approx. degeneracy is TESTABLE
Inverted hierarchy is TESTABLE
cosmo
Normal hierarchy is NOT TESTABLE
from F. Feruglio, A. Strumia, F. Vissani ('02)
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Leptogenesis
Boris Kayser
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Basic Idea of Leptogenesis
Fukugita,Yanagida

• Right-handed neutrinos are produced in early
  universe and decay out of equilibrium giving net
  lepton numbers Le , L? , L?
• CP violation from complex Yukawa couplings
• Out of equilibrium Boltzmann eqs lead to Le , L?
  , L? partial washouts
• Surviving Le, L? , L? are processed into B via
  B-L conserving sphalerons

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Allowed regions of TRH and MR1 in MSSM
Assumes maximal asymmetry and optimal washout
Antusch,Teixeira
Gravitino problem if TRHgt106 GeV
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Motivation to go beyond MSSM

• Exceptional Supersymmetric Standard Model
• - Solves ? problem of MSSM
• Solves fine tuning problem of MSSM
• Predicts Z, exotic D quarks, exotic L leptons
  at LHC
• Solves gravitino problem in leptogenesis (in
  progress)

Extra diagrams contribute to leptogenesis
SFK,Luo,Miller,Nevzorov
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Typical Spectrum
Athron,SFK,Miller,Moretti,Nevzorov
non-Higgs
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The Origin of the Universe

• Right-handed scalar neutrino as inflaton Vm2?
  giving r0.16, ns0.96 (Murayama,Suzuki,Yanagida,Y
  okoyama)
• Or sneutrino hybrid inflation r0, ns 0.9-1.0
  (Antusch, Bastero-Gil, SFK, Shafi)

Rachel Bean et al
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Conclusion

• 1998-2008 is the golden age of neutrino
  oscillations neutrino mass and mixing (beyond
  SM)
• Goal of next generation of oscillation
  experiments is to show that the deviations from
  TBM r,s,a are non-zero
• Challenge for future is to accurately measure
  r,s,a and ? to relate them to each other and to
  the Wolfenstein ?
• High precision experiments will be required
  (reactor, LBL, neutrinoless DBD)
• Challenge for particle theory is to understand
  the origin of the small neutrino mass and the
  large mixing
• Implications for GUTs and Flavour Models leading
  to testable predictions e.g. sum rule
• Implications for origin of matter and the Universe