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 ’s: neutrinos intensively used to probe nucleon structure 1990: 3 families of neutrinos from Z 0 width 2000: Third flavor (  ) is observed MINIMAL STANDARD MODEL: 3 families of massless neutrinos : 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  <  B Also: recent projects using 20 kg of tritium with TPC/MicroMegas detector

Neutrinoless double beta decays NEMO experiment in Frejus tunnel best present limit: 76 Ge (HM) m eff < eV expected sensitivity 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(-iE 1 t) cos  | 1 > + exp(-iE 2 t) sin  | 2 > P( e –>  ) = | | 2 = sin 2 2  sin 2 (  m 2 /4E t)  m   m 1 2 –m 2 2 L osc (m) = 2.5 E (MeV) /  m 2 (eV 2 )

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  m 2 = eV 2

Sudbury Neutrino Observatory

KAMLAND

The atmospheric neutrinos Maximal oscillation between  and  with  m 2 = eV 2

p + Azote  pions        e    e Au niveau du sol: 2  pour 1 e

SuperKamioka

Separation e/ 

First generation of long baseline experiments

Mixing matrix: the missing parameters 1   e          l = U l i i U is a unitary matrix: 3 angles :  12,  13,  23 plus 1 CP violating phase  3 masses m 1, m 2, m 3 SUN :   m 12 2 = eV 2,  12 ~ 35 o ATM :  m 23 2 = eV 2,  23 = 45 o Missing :  13 and the phase  both govern the    e oscillation at the atmospheric frequency We know that  13 is < 10 o we have to look for a small oscillation

Neutrino superbeams Strategy to measure  13 : Build an intense neutrino beam using a high power proton driver Install a detector at the oscillation maximum L opt = 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 6 He 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 P osc (neutrinos) = |A| 2 + |S| A S sin  P(antineutrinos) = |A| 2 + |S| 2 – 2 A S sin    (frequence atmospherique) B = 0.02 (oscillation solaire)