NEUTRINO PROPERTIES

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NEUTRINO PROPERTIES
J.Bouchez CEA-Saclay
Eurisol town meeting Orsay, 13/5/2003
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Brief history of the neutrino(s)
1930 Pauli postulates the neutrino (energy
conservation in b decays) 1934 Fermi builds a
theory of beta decays 1956 Cowan and Reines
discover the neutrino (emitted by nuclear
reactors) 1955 Maximal parity violation in b
decays 1956 V-A theory only left-handed
neutrinos interact 1962 Second variety (or
flavor) of neutrinos nm ? ne 1970-1990s
neutrinos intensively used to probe nucleon
structure 1990 3 families of neutrinos from Z0
width 2000 Third flavor (nt) is
observed MINIMAL STANDARD MODEL 3 families of
massless neutrinos 1998-2000 neutrinos have a
mass
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What we know and what we want to know
? most probably 3 families of light standard
(V-A) neutrinos ne, nm, nt ? neutrinos are
massive we know splittings between square
masses ? absolute mass scale? -gt fondamental for
cosmology and unification scheme of
interactions ? are neutrinos their own
antiparticle (Majorana neutrinos) or not (Dirac
neutrinos) (for Majorana neutrinos, neutrinos
and antineutrinos differ only by their
helicity) ? what is the magnetic moment of the
neutrinos? ? are neutrinos stable? ? relation
between neutrino flavor eigenstates and mass
eigenstates (mixing matrix) only partially
known ? Is there CP violation in the neutrino
sector? (LEPTOGENESIS)
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Which experiments ?
? absolute mass scale time of flight Supernova
1987A mlt 20 eV end of electron beta spectrum
Tritium mlt 2.5 eV Fluctuations of
Cosmological Microwave Background WMAP mlt0.23
eV ? Dirac/Majorana search for neutrinoless
double beta decay (possible clue to absolute mass
scale) ? Magnetic moment neutrino diffusion on
electron at low energy ? Mixing matrix, mass
splittings, CP violation flavor oscillations
Use all possible neutrino sources Sun, reactors,
atmospheric showers, accelerators of various
energies
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Magnetic moment of neutrinos
MUNU experiment at Bugey reactor
mn lt 1.2 10-10 mB
Also recent projects using 20 kg of tritium with
TPC/MicroMegas detector
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Neutrinoless double beta decays
NEMO experiment in Frejus tunnel
best present limit 76Ge (HM) m eff lt
0.4-0.8 eV
Future projects towards 1 ton of
isotopes (CUORE, GENIUS) 0.01 eV ??!!
expected sensitivity 0.2-0.4 eV
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Flavor oscillations
negt cos? n1gt sin ? n2gt nmgt sin?
n1gt cos ? n2gt n(t0)gt negt n(t)gt
exp(-iE1t) cos? n1gt exp(-iE2t) sin? n2gt
P(ne gtnm) ltnmn(t)gt2 sin22? sin2 (Dm2/4E
t) Dm 2 m12 m22
L osc (m) 2.5 En (MeV) / Dm2(eV2)
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The solar neutrinos
All experiments (Homestake, GALLEX, SAGE, SuperK)
have found an important deficit for the flux of
solar ne SNO has measured the total neutrino
flux (neutral current on deuterium and found NO
deficit KamLand has confirmed a nearly maximal
oscillation for reactor antineutrinos over 200
km PROOF OF FLAVOUR OSCILLATIONS with Dm2 7
10-5 eV2
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Sudbury Neutrino Observatory
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KAMLAND
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The atmospheric neutrinos
Maximal oscillation between nm and nt with Dm2
2.5 10-3 eV2
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• p Azote ? pions
• p ? m nm
• m ? e nm ne

Au niveau du sol 2 nm pour 1 ne
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SuperKamioka
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SuperKamioka
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Separation e/m
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First generation of long baseline experiments
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Mixing matrix the missing parameters
n3
3 masses m1, m2, m3
nm
SUN Dm122 7 10-5 eV2 , ?12 35o ATM
Dm232 2.5 10-3 eV2 , ?23 45o
nt
?23
ne
n2
?13
Missing ?13 and the phase d both govern the nm
?? ne oscillation at the atmospheric
frequency We know that ?13 is lt 10o
?12
n1
nl Ul i ni
U is a unitary matrix 3 angles ?12 , ?13 ,
?23 plus 1 CP violating phase d
we have to look for a small oscillation
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Neutrino superbeams
Strategy to measure ?13 Build an intense
neutrino beam using a high power proton
driver Install a detector at the oscillation
maximum Lopt 500 km x En (GeV) ? The
detector should be installed deep underground ?
For sensitivities of 1 degree on ?13 , its mass
should be about 1 megaton ? only realistic
technique Water Cerenkov ? bonus
unprecedented sensitivity on proton lifetime and
SN explosions Projects ? USA NuMI off-axis
FNAL injector (0.4 MW) fine grained calorimeter
(50 kt) MI upgrade ? BNL superbeam ? ?
Japan JHF n proton driver 0.8 MW
SuperKamioka upgrade to 4 MW and
HyperKamioka (1 MTon) ? Europe CERN SPL (4 MW)
Water Cerenkov (0.5 to 1 Mton) at Frejus
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Neutrino beta beams
A new idea by Piero Zucchelli Produce intense ne
(anti-ne) beams by accelerating (G around 70) and
storing radioactive ions in a storage
ring Advantages ? strongly collimated neutrino
beams ( Q G / Q ) ? perfectly known spectrum
(beta decay) ? very high flavor purity With
present technologies, an anti-ne beam produced
by 6He is competitive with the SPL superbeam
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Superbeam / betabeam synergy
search for CP violation
with only superbeam run 3 years in neutrinos
and 7 years in antineutrinos compare nm ? ne and
anti-nm ? anti-ne with superbeam and beta
beam run 10 years and study simultaneously nm ?
ne with the superbeam and ne ? nm with the beta
beam (using 18 Ne )
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Can betabeams do everything ?
Very recently, it has been suggested to store
simultaneously ( with no intensity loss ) both
6 He and 18 Ne in the same storage ring. This
opens the possibility to study CP violation with
only beta beams Potentialities are presently
under study (compromise on beam energies)
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CP violation sensitivity
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CP and oscillations

• Posc(neutrinos) A2 S2 2 A S sin d
• P(antineutrinos) A2 S2 2 A S sin d
• 1.4 ?13 (frequence atmospherique)
• B 0.02 (oscillation solaire)