Transcript Diapositive 1

Neutrino Physics
Alain Blondel University of Geneva
1. What are neutrinos and how do we know ?
2. The neutrino questions
3. Neutrino mass and neutrino oscillations
4. neutrino oscillations and CP violation
5. on-going and future neutrino experiments on oscillations
6. on-going and future neutrino-less double-beta experiments
7. Conclusions
Neutrino physics -- Alain Blondel
Les neutrinos interagissent très peu et ont une masse extrêmement faible. Pourtant
il se pourrait bien qu'ils détiennent la clé de plusieurs questions fondamentales en
physique des particules. On passera en revue les expériences les plus marquantes
par lesquelles les propriétés des neutrinos ont été établies, puis on fera un bilan
des questions actuelles et du programme d'expériences prévu pour y répondre.
1. Propriétés des neutrinos: découverte, hélicité, neutrinos et antineutrinos, les
familles de neutrinos.
2. Interactions des neutrinos, courant charges et courants neutres, les neutrinos
dans le Modèle Standard.
3. La découverte des neutrinos du soleil, et le mystère des neutrinos solaires. Les
neutrinos atmosphériques et la découverte des transmutations de neutrinos.
4. Propriétés des neutrinos massifs, les oscillations. Oscillations de neutrino
oscillations avec trois familles. Les expériences neutrino auprès des réacteurs
nucléaires.
5. La recherche de l'angle manquant theta_13. Les effets de matière et la violation
de CP, le programme expérimental futur sur les oscillations.
6. Les mesures directes de la masse des neutrinos. Les neutrinos et la cosmologie.
7. Questions théoriques sur les masses des neutrinos, masses de Dirac ou de
Majorana ? La recherche de la désintégration double beta sans neutrinos. Envoi
sur le rôle des neutrinos pour façonner l'univers.
Evaluation
Examen oral.
Sessions : Juin - Août/Septembre ECTS : 3.5
Neutrino physics -- Alain Blondel
Neutrinos have mass and mix
This is NOT the Standard Model
why cant we just add masses to neutrinos?
Neutrino physics -- Alain Blondel
i i
Majorana neutrinos
or
i i
Dirac neutrinos?
e+  e– since Charge(e+) = – Charge(e–).
   any conserved charge-like
But neutrinos may not carry
quantum number.
There is NO experimetal evidence or theoretical need for
a conserved Lepton Number L as
L(ν) = L(l–) = –L(ν) = –L(l+) = 1
i
then, nothing distinguishes
i
i
from
i
violation of fermion number….
!
Neutrino physics -- Alain Blondel
Adding masses to the Stadard model neutrino 'simply' by adding a Dirac
mass term
implies adding a right-handed neutrino.
No SM symmetry prevents adding then a term like
and this simply means that a neutrino turns into a antineutrino
(the charge conjugate of a right handed antineutrino is a left handed neutrino!)
this does not violate spin conservation since a left handed field has a component
of the opposite helicity (and vice versa)
L  - + + m/E
Neutrino physics -- Alain Blondel
In the most general way:
MR  0
mD  0
Dirac + Majorana
MR  0
mD = 0
Majorana only
MR = 0
mD  0
Dirac only, (like e- vs e+):
m
L R
R L
Iweak= ½ 0
½ 0
4 states of equal masses
Some have I=1/2 (active)
Some have I=0 (sterile)
m
L
R
Iweak= ½
½
2 states of equal masses
All have
I=1/2 (active)
MR  0
mD  0
Dirac + Majorana
m
Iweak=
L NR
R NL
½ 0
½ 0
4 states , 2 mass levels
m1 have I=1/2 (active)
m2 have
I=0 Blondel
(sterile)
Neutrino physics
-- Alain
Note that this is not necessary
As one can have M anywhere…
Neutrino physics -- Alain Blondel
Neutrinos : the New Physics there is… and a lot of it!
SM
L
I= ½
Dirac mass term
only
R
½
L R
½ 0
R L
½ 0
Majorana
mass term only
L
½
‘R ‘
½
Dirac AND Majorana
Mass terms
NR
0
L
½
X 3 Families
6 massless states
wrong
NL
0
R
½
X 3 Families
X 3 Families
X 3 Families
3 masses
12 states
3 active neutrinos
3 active antinu’s
6 sterile neutrinos…
3 mixing angles
1 CP violating phase
0v = 0
3 masses
6 active states
No steriles
3 mixing angles
3 CP violating phases
0v  0
6 masses
12 states
6 active states
6 sterile neutrinos…
More mixing angles
and CPV phases
0v  0
 Leptogenesis and
Dark matter
Mass hierarchies are all unknown except m1 < m2
Preferred scenario has both Dirac and Majorana terms …
… many physics possibilities and experimental challenges
The mass spectrum of the elementary particles. Neutrinos are 1012 times
lighter than other elementary fermions. The hierarchy of this spectrum
remains a puzzle of particle physics.
Most attractive wisdom: via the see-saw mwchanism,
the neutrinos are very light because they are low-lying states
in a split doublet with heavy neutrinos of mass scale interestingly
similar to the grand unification scale.
m M  <v>2
with <v> ~= mtop =174 GeV
 for m. O(10-2) eV  M ~1015 GeV
Neutrino physics -- Alain Blondel
One often considers that MR ~ MGUT ~ 1010 to 1015 GeV
Neutrino physics -- Alain Blondel
Pion decay with massive neutrinos
p+
m+
p+
L
+
m+
L
Lc = R
(m /E)2
1
(.05/30 106)2 = 10-18
no problem
Neutrino physics -- Alain Blondel
e
would measure a distribution with three
values of mass with the following
probabilities
¦U1e¦2 ¦U2e¦2
The smallest possible flavor neutrino mass?
<m
Valeurs présentes
1
2
2
e>=¦U1e¦
¦U3e¦2
m1 + ¦U2e¦2 m2 + ¦U3e¦2 m3
3
Neutrino physics -- Alain Blondel
m
Neutrino physics -- Alain Blondel
have Majorana mass term
Neutrino physics -- Alain Blondel
Neutrino physics -- Alain Blondel
ce que mesure le 0
est <m> :
m1 m2 m3 are physical masses
of active neutrino (I=1/2)
which in this case are just the same
as in oscillation experiments
(GF)4
Vertex
emission
Deposited energy:
E1+E2= 2088 keV
Internal hypothesis:
(Dt)mes –(Dt)theo = 0.22 ns
Common vertex:
(Dvertex) = 2.1 mm
NEMO
Criteria to select  events:
• 2 tracks with charge < 0
• 2 PMT, each > 200 keV
• PMT-Track association
• Common vertex
• Internal hypothesis (external event rejection)
• No other isolated PMT (g rejection)
• No delayed track (214Bi rejection)
typical 2 evenement
GIF2004 Alain Blondel
Neutrino physics -- Alain Blondel
Neutrino physics -- Alain Blondel
Neutrino physics -- Alain Blondel
GERDA has accumulated enough statistics now to confirm of not HdM result by summer 2013
Neutrino physics -- Alain Blondel
Neutrino physics -- Alain Blondel
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Neutrino physics -- Alain Blondel
Neutrino physics -- Alain Blondel
Neutrino physics -- Alain Blondel
Neutrino physics -- Alain Blondel
Neutrino physics -- Alain Blondel
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KAMLAND
Neutrino physics -- Alain Blondel
Neutrino physics -- Alain Blondel
Neutrino physics -- Alain Blondel
Sterile neutrinos ( right handed neutrinos)
Sterile neutrinos can have masses extending from
(essentially 0) all the way to GUT-inspired 1010 GeV!
We have many hints for ‘something that could be indications for
sterile neutrinos ‘ in the ~ few eV2 range
In general these hints are not performed with the desired
methodological quality
-- no near detector
-- no direct flux measurement
-- no long target hadroproduction with full acceptance
-- etc.. etc…
-- none is 5 sigma
-- need decisive experiments (> 5 significance)
-- look wide! other ranges than LSND ‘effect’
Alain Blondel NUFACT12 23-07- 2012
1989 The Number of light neutrinos
e+e-  Z  qq , vs
e+e-  Z 
ALEPH+DELPHI+L3+OPAL in 2001 N = 2.984 0.008
Error dominated by systematics on luminosity.
At the basis of the experiment: background to golden channel is low, because there is no known neutrino
interaction that produces a fast electromagnetic signal followed by a ‘slow neutron’ capture signal
However we do not know all neutrino reactions at these low energies.
Neutrino physics -- Alain Blondel
Can be fit by oscillation signal
Neutrino physics -- Alain Blondel
Alain Blondel NUFACT12 23-07- 2012
Thierry Lasserre
Alain Blondel NUFACT12 23-07- 2012
Shaewitz Neutrino 2012
Alain Blondel NUFACT12 23-07- 2012
Sterile neutrino search a global view:
Detected by mixing between sterile and active neutrino
ideal experiments:
source
known process
active, 
0. if sterile cannot
be produced (too heavy)
apparent deficit
in decay rate
detector
known process
sterile
active, 
1. disappearance,
not necessarily
oscillatory
best is
NC disappearance
2.   appearance
(at higher order)
Alain Blondel NUFACT12 23-07- 2012
Alain Blondel NUFACT12 23-07- 2012
CONCLUSIONS
1. Neutrinos were a cornerstone of the construction of the Standard Model
helicity of neutrinos is LEFT (???)
discovery of neutral currents and determination of nucleon structure of quarks
2. Neutrinos have mass
there is no unique answer to this in the Standard Model
Dirac or Majorana mass term, or both?
3. There are three families of neutrinos and they mix
This is the source of neutrino oscillations
and could lead to observable CP violation
4. If neutrinos have both Majorana and Dirac mass terms
A possible explanation of small masses of active neutrinos
Predicts the existence of neutrinoless double beta decay
Predicts the existence of massive sterile neutrinos
5. AND….
Provide a beautiful dark matter candidate
Provide an explanation for the matter-antimatter asymmetry of the Univers
Neutrino physics -- Alain Blondel