CONTENTS

1
Neutrino Oscillations Experimental Status
CONTENTS
I Formalism of neutrino oscillations II
Overview of the experimental situation III
Discussion and outlook
P. Vilain
2
Neutrino mixing and oscillations
3
Usual parametrization of the P-MNS matrix U
Pontecorvo(1957) Maki,Nakagawa,Sakata (1962)
1 Dirac phase
2 Majorana phases
NOTE - oscillation expts not sensitive to
Majorana phases - CP violation
phase ? not observable if ?13 0 -
in effective 2? formalism 1 angle ? à la
Cabbibo
4
From Y. Smirnov
Simplified ( 2 families) picture
Mixing angle
n2 sinq ne cosq nm
ne cosq n1 sinq n2
inversely
n1 cosq ne - sinq nm
nm - sinq n1 cosq n2
coherent mixtures of mass eigenstates
flavor composition of the mass eigenstates
n2
ne
n2
n1
n1
n2
nm
n1
Interference of the parts with the same
flavor depends on the phase difference
Df between n1 and n2
Propagation in vacuum
Due to difference of masses n1 and n2 have
different phase velocities
the phase difference increase will change the
interference pattern
oscillations
5
Propagation in vacuum (2 families, for instance
?e and ?? )
() A more serious quantum mechanical treatment
with wave packets give the same result for all
practical situations
6
In practical units
7
Damping
Distortion of the energy spectrum
8
General 3? Oscillation probability
9
If strong mass hierarchy effective 2-family
approximation
Physics governed by ? Dm2
? flavor composition of n3 only
10
Matter effects (very simplified)
Elastic forward scattering

Potentials
Ve ? Vm due to
ne density of electrons
Refraction length
Eigenstates in matter
depend on ne, E
IF Vacuum oscill. Length Refraction length
Resonance with maximal mixing
IF density changes slowly enough on the way of
neutrinos like in the Sun or the Earth
MSW adiabatic conversion
Mikheyev,Smirnov(1986) Wolfenstein(1978)
11
From Y. Smirnov
In the Sun 3 regimes depending on E?

P sin2 q
n0 gtgt nR
Non-oscillatory transition
n2m n1m
n2 n1
interference suppressed
Resonance
Mixing suppressed
n0 gt nR
Adiabatic conversion oscillations
n2m n1m
n2 n1
n0 lt nR
Small matter corrections
n2m n1m
n2 n1
ne
12
II Overview of the experimental situation
- Solar ? - Reactor ? -
Atmospheric ? - Accelerator ?
- (Supernova ?, UHE ?)
Oscillation of
13
Solar Neutrino Experiments
Solar neutrinos spectrum Detectors / experiments
thresholds
Super-K, SNO Cerenkov
Homestake
GALLEX,GNO,SAGE
14
Low threshold radio-chemical counting experiments
The glorious Homestake expt (1968-99) 31
years of datataking, 2000 int.ions
Gallium experiments GALLEX, GNO (
Gran Sasso) 1992-97 1998-
SAGE (Baksan mine) 1991-
15
Real-time water Cerenkov experiments Kamiokande
II Super-K 1987-95
1996-
16
Sudbury Neutrino Observatory (SNO) 2001-
Nucl-ex/0309004 SNO Coll. Hep-ph/0309130
Maltoni et al
NEW!
17
Measured event rates v.z.SSM predictions (Bahcall
et al.)
18
SNO 2002 evidence for FLAVOR CHANGE
19
Best oscillation fit (pre-SNO)
All data combined
LMA (MSW) solution
Dm2 6.8 10-5 eV2
tan2q 0.40
20
Reactor Neutrino Experiments
No effect seen
21
KamLAND several reactors at more than 100 km
? Sensitive to the LMA Solar parameters
22
R versus mean reactor distance
solar data KamLAND
Nobs NBG Nno-OSC
0.611 0.085 (stat) 0.041 (syst)
Nice confirmation - with - independent
of solar matter effects
LMA solar parameters
23
Atmospheric Neutrino Experiments
Within small computable corrections Up/Down
flux symmetry at ? production F(q) F(p-q) q
zenith angle But beam composition and spectra
relies on models
24
By far most complete and precise results provided
by Super-Kamiokande
SK can distinguish e-like events fuzzy Cerenkov
ring ?-like events
sharp measure
E(e or ?) and ? (e or ?)
Sub-GeV e-like
Sub-GeV m-like
Zenith angle distributions
96 0.6 GeV
87 0.6 GeV
Best ????? fit No oscillation
Multi-GeV e-like
Multi-GeV m-like FC
Purity ltEgt
84 7 GeV
99 7 GeV
25
Fit assuming
Limits on ?13
90 c.l.
26
Accelerator Neutrino Experiments
1)
Data taking going on
K2K the KEK to Kamioka experiment
No Oscillation
Best oscill. fit
27
Neutrino oscillation at accelerator beam dumps
2)
28
LSND experiment _at_ LANSCE, Los Alamos
Situation still unclear
167 tons liquid scintillator ltLgt 29 m Data
till 1999
Karmen-II experiment _at_ ISIS, Rutherford Lab
56 tons liquid scintillator ltLgt 15 m Data
till 2001
Wait 2005 results from MiniBoone (FNAL)
WMAP limit
IF signal confirmed need a sterile ?
29
3)
Search for ?? appearance at high E accelerator

30
Out of 106 events
31
III Discussion and outlook (ignoring LSND)
32
All wrong!
Rather a surprise !
?3
?2
?1
33
The next steps
a) Increase precision on solar parameters

• SNO Neutron Capture Detectors (He3 counters)
• KamLand more statistic ( geothermic ? ?)

b) Check the E dependance of solar survival
prob.ty

• KamLand Borexino decrease threshold to detect
  solar Be7 ?
• (But background from radioactivity?)
• pp neutrinos real-time detection
• some ideas but difficult
• SNO, SK threshold down to 4 MeV?

34
c) See the oscillation dip
In 2005 L750 km FNAL to Soudan mine ltEgt a
few GeV
35
d) Observe the ?? appearance
CNGS beam in 2006 L750 km (CERN to Gran
Sasso) ltEgt
20 GeV
ICARUS
Liquid Argon TPC very good e-shower identificati
on kinematics ? Separate ?e CC and ?? CC (with
??e)
36
OPERA
37
A hybrid experiment
38
e) Improve the limit on sin2 2?13 (now 0.1)
Crucial for the design of future big experiments
!

• 2 ways to reach 0.01
• Chooz-like reactor expt with 2 detectors
• (to lower systematics on ? flux)

Several sites being discussed

• Long Baseline ?e appearance
• (MINOS, ICARUS, OPERA)

39
Some remaining big questions
Mass hierarchy normal or inverted ?
Earth matter effects
Long Baseline
through earth matter Effect strongly
depends on sin2 2?13
40
CP violation ?CP ? 0 ?
Long Baseline
through earth matter Strongly depends on sin2
2?13 and correlated with matter effects
41

• To disentangle the two questions, one needs
• very pure and intense beams
• several experiments at different (and large) L/E
• very big detectors
• A lot of money..

PROJECTS - Off-axis experiments
- Superbeams -Neutrino
Factory (RD phase)
42
Off-axis Experiments

• putting a detector (at large L) slightly
  off-axis w.r.t. the ? beam
• ? lower rate BUT - lower energy ? less background
  from ?0
• - narrow
  energy range (from ? ? ?? kinematics)
• Well suited for studies of
• For instance NuMI Beam at 750 km

On axis
10 km off-axis
E(GeV)
E(GeV)
43
Superbeams
very high intensity proton beams LBL
(off-axis) experiment
J-PARC neutrino project - 50 GeV Proton
Synchrotron at JAERI (near KEK) - phase 1
(approved) 0.75 MW 100 K2K
1 GeV ? beam to SuperK (L 295km) -
phase 2 (RD) 4 MW ! 100
phase 1 beam to Hyper-K 1 Mton !
CERN study - 4 MW 2 GeV proton LINAC
- 300 MeV ? beam to Fréjus underground lab.
(L130 km) - large ( 400 kton) water
Cerenkov detector
44
Neutrino factory Muon storage ring
45
Absolute mass scale ?
Tritium ? decay end-point
46
status of present tritium experiments
Troitsk
Mainz gaseous T2-source
quench-condensed solid
T2-source
electrostatic retarding spectrometers with
magnetic adiabatic collimation
analysis 1994-99, 2001
analysis 1998/99, 2001
both experiments have reached their intrinsic
limit of sensitivity
New proposal KATRIN much larger spectrometer
(10 m ? !) to reach 0.2 eV sensitivity
47
All masses linked to lightest by oscillations
H. Robertson
48
Neutrinoless Double-beta Decay
Dirac or Majorana ?
Calculation of nuclear matrix elements
49
Moscow-Heidelberg experiment Example of active
source experiment
5 Ge crystals diodes total 11 kg - 86 enriched
76Ge in Gran Sasso Laboratory
?(E) ? E 0.7 10-3
Present status upper limits
50
Many other experiments in preparation

• NEMO3
• CUORE
• MAJORANA
• GENIUS
• COBRA
• MOON
• EXO
• XMASS

7 kg 100Mo tracking and calorimetry
Cryogenic calorimetry in TeO2 crystals
Robust and well known Ge technique Requires 500kg
(10ton?)of Enriched Ge
Cd(Zn)Te semiconductor
34 ton Mo sheets
1(10) ton enriched Xe in TPC
10 ton liquid Xe
Sensitivities varying from 0.5 eV down to 0.05 ev
Background is a challenge!
51
Conclusions

• Enormous progress in recent years
• Solar neutrino problem solved!
• Still some loose ends
• Many forthcoming experiments
• Three-generation scenario is most probable
• but LSND not yet ruled out
• Absolute mass scale from beta decays or
  cosmology?
• Next q13 key to mass hierarchy, CP violation
• Long-baseline or reactor
• New super beams

THEORY on origin of masses and mixings ?