NEUTRINO PROPERTIES

J.Bouchez

CEA-Saclay

Eurisol town meeting

Orsay, 13/5/2003

Brief history of the neutrino(s)1930: Pauli postulates the neutrino (energy conservation in 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 decays

1956: V-A theory : only left-handed neutrinos interact

1962: Second variety (or flavor) of neutrinos : ≠ e

1970-1990’s: neutrinos intensively used to probe nucleon structure

1990: 3 families of neutrinos from Z0 width

2000: Third flavor () is observed

MINIMAL STANDARD MODEL: 3 families of massless neutrinos

1998-2000: neutrinos have a mass

What we know and what we want to know

● most probably 3 families of light standard (V-A) neutrinos: e

● neutrinos are massive: we know splittings between square masses

● absolute mass scale?

-> 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)

Which experiments ?● absolute mass scale:

time of flight: Supernova 1987A m< 20 eV

end of electron beta spectrum : Tritium m< 2.5 eV

Fluctuations of Cosmological Microwave Background: WMAP m<0.23 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……

Magnetic moment of neutrinos

MUNU experiment at Bugey reactor

< 1.2 10-10 B

Also: recent projects using 20 kg of tritium with TPC/MicroMegas detector

Neutrinoless double beta decaysNEMO experiment in

Frejus tunnelbest present limit: 76Ge (HM)

m eff < 0.4-0.8 eV

expected sensitivity

0.2-0.4 eV

Future projects:

towards 1 ton of isotopes

(CUORE, GENIUS)

0.01 eV ??!!

Flavor oscillations |e> = cos |1> + sin |2> |> = – sin |1> + cos |2>

|(t=0)> = |e> |(t)> = exp(-iE1t) cos |1> + exp(-iE2t) sin |2>

P(e –>) = |<|(t)>|2 = sin22 sin2 (m2/4E t)

mm12 –m2

2

L osc (m) = 2.5 E (MeV) /m2(eV2)

The solar neutrinos

All experiments (Homestake, GALLEX, SAGE, SuperK) have found an important deficit for the flux of solar e

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 m2 = 7 10-5 eV2

Sudbury Neutrino Observatory

KAMLAND

The atmospheric neutrinos

Maximal oscillation between and with m2 = 2.5 10-3 eV2

p + Azote pions

e e

Au niveau du sol:

2 pour 1 e

SuperKamioka

SuperKamioka

Separation e/

First generation of long baseline experiments

Mixing matrix: the missing parameters

1

e

l = Ul i i

U is a unitary matrix:

3 angles : 12 , 13 , 23

plus 1 CP violating phase

3 masses m1, m2, m3

SUN : m122 = 7 10-5 eV2 , 12~ 35o

ATM : m232 = 2.5 10-3 eV2 , 23 = 45o

Missing : 13 and the phase

both govern the e oscillation at the atmospheric frequency

We know that 13 is < 10o

we have to look for a small oscillation

Neutrino superbeamsStrategy 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 E (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 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

Neutrino beta beams

A new idea by Piero Zucchelli

Produce intense e (anti-e) beams by accelerating ( around 70) and storing radioactive ions in a storage ring

Advantages:

● strongly collimated neutrino beams ( Q = / 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

Superbeam / betabeam synergy

search for CP violation:

with only superbeam:

run 3 years in neutrinos and 7 years in antineutrinos

compare e and anti- anti-e

with superbeam and beta beam:

run 10 years and study simultaneously

e with the superbeam and

e with the beta beam (using 18 Ne )

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)

CP violation sensitivity

CP and oscillations

Posc(neutrinos) = |A|2 + |S|2 + 2 A S sin

P(antineutrinos) = |A|2 + |S|2 – 2 A S sin

(frequence atmospherique)

B = 0.02 (oscillation solaire)