esign esign The Standard Model e ( e ) ( ) ( ) Flavor - PowerPoint PPT Presentation

IS THE NEUTRINO A MAJORANA OR A DIRAC PARTICLE ? Ettore Fiorini, Bologna June 17 2005 ν=ν− or ν � ν− Lepton number conservation or violation Has neutrino a finite mass 100 % chirality ν ν− → → ⇐ ⇐ ⇐ ⇐ � � � � esign esign

The Standard Model ν e (ν � e ) ν µ (ν � µ ) ν τ (ν �� τ ) Flavor conservation or violation Neutrino oscillations need m ν � 0 ν e ν µ ν e ν τ 2 2 ∆ m (eV ) L(km / m ) 2 2 ab ν ν − > θ P( - ) sin 2 sin ( 1 . 27 ) a b E ( GeV/ MeV )

Neutrino oscillations have been observed with solar, atmosperic and reactor neutrinos

ATMOSPHERIC NEUTRINOS Superkamiokande and MACRO Reactor and long baseline experiments Neutrino factories

2 � � 0 2 But oscillation experiments only indicate that m ν 0 But oscillation experiments only indicate that m ν ν ν ν ν ν ν to determine < m m ν > => double beta decay to determine < ν > => double beta decay ν ν ν ν ν ν 1. (A,Z) => (A,Z+2) + 2 e - + 2 ν ν e ¯ ν ν 2. (A,Z) => (A,Z+2) + 2 e - + χ χ ( …2,3 χ χ χ χ χ χ) 3. (A,Z) => (A,Z+2) + 2 e - (A,Z+1) (A,Z) (A,Z+2)

u u e - d d e - W ν ν ν ν e W ν e ν W e e - d ν e ν ν ν W d e - u u 0 ν ν - ββ ν ν ββ decay ββ ββ 2 ν ν - ββ ββ decay ν ν ββ ββ Neutrinoless ββ decay

Neutrinoless ββ decay would imply a non zero effective majorana neutrino mass as indicated by oscillation experiments

Experimental approaches Geochemical experiments i82 Se = > 82 Kr, 96 Zr = > 96 Mo (?) , 128 Te = > 128 Xe (non confirmed), 130 Te = > 130 Te Radiochemical experiments 238 U = > 238 Pu (non confirmed) Direct experiments Source ≠ ≠ detector ≠ ≠ Source = detector (calorimetric) detector e - source e - e - detector Source ≠ Detector e -

Cryogenic detectors heat bath Thermal sensor absorber crystal Incident particle

V T 3 = C 1944 ( )( ) J/K V Τ Vm D 2 ∆ = ξ E k C T V ∆Ε @ 5 keV ~100 mk ~ 1 mg <1 eV ~ 5 eV @ 2 MeV ~10 mk ~ 1 kg <10 eV ~ keV

Recent experiments on ββ0ν τ τ 1/2 τ τ 0 ν ν (y) ν ν Experim Isotope m* ee (eV) Range m ee > 1.9 × × 10 25 × × < 0.35 < 0.3 – 2.5 Heidelberg – Moscow 2001 76 Ge > 1.57 × × 10 25 × × < 0.38 < 0.3 – 2.5 IGEX 2002 > 2.1 × × 10 23 × × Mi DBD – ν ν 2002 ν ν 130 Te < 1.5 < 0.9 – 2.1 > 7.7 × × × × 10 24 128 Te ��� < 1.0 < 1.0 – 4.4 Bernatowicz et al. 1993 (GEO) > 1.2 × × 10 24 × × 136 Xe < 1.0 < 0.8 – 2.4 Belli et al. 2003 > 1.7 × × 10 23 × × 116 Cd < 1.7 < 1.6 – 5.5 Bizzeti et al. 2003 > 5.5 × × 10 22 × × 100 Mo < 4.8 < 1.4 - 256 Ejiri et al. 2001 > 1.8 × × 10 22 × × 48 Ca < 6.0 Osawa I. et al. 2002 * Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31 Τ = 1.2 x 1025 a => <m ν > ~ 0.44 eV The “Klapdor ” effect =>

Two new experiments NEMO III e CUORICINO

Searches with thermal detectors CUORE R&D (Hall C) CUORE (Hall A) Cuoricino (Hall A)

Crescita della massa dei bolometri total mass [kg] year

� Search for the 2 β | o ν in 130 Te (Q=2529 keV) and other rare events � At Hall A in the Laboratori Nazionali del Gran Sasso (LNGS) � 18 crystals 3x3x6 cm3 + 44 crystals 5x5x5 cm3 = 40.7 kg of TeO2 � Operation started in the beginning of 2003 => ~ 4 months � Background .18±.01 c /kev/ kg/ a ν ( 130 Te) > 1.8x 10 24 y <m ν 0 ν ν ν � T 1/2 ν > .2 -1. 1 ν ν Klapdor 0.1 – 0.9 2 modules, 9 detector each, 11 modules, 4 detector each, crystal dimension 3x3x6 cm 3 crystal dimension 5x5x5 cm 3 crystal mass 330 g crystal mass 790 g 9 x 2 x 0.33 = 5.94 kg of TeO 2 4 x 11 x 0.79 = 34.76 kg of TeO 2

Present Cuoricino region Arnaboldi et al., submitted to PRL, hep-ex/0501034 (2005). Possible evidence (best value 0.39 eV) With the same matrix elements the Cuoricino limit is 0.53 eV “quasi” degeneracy � � ≈ � �� ≈ � � Inverse hierarchy ∆ � � �� �� ∆ � � ��� Direct hierarchy ∆ � � �� �� ∆ � � ��� Cosmological disfavoured (WMAP) region Feruglio F. , Strumia A. , Vissani F. hep-ph/0201291

The CUORE project ��� �������������� ��������� �� �� ����� ��� � �������� 750 kg TeO 2 => 600 kg Te => 203 kg 130 Te ������������������������������ ��

����������� The discovery of neutrino oscillations to which ∆ m 2 � 0 Masatoshi contributed so much exists and ∆ ∆ ∆ We need to determine the Majorana nature of the neutrino and the absolute value of <m ν ν > ν ν Neutrinoless double beta decay would indicate not only lepton number violation , but also < < < m ν < ν > > � 0 > > ν ν This process has been indicated by an experiment (Klapdor) with a value of ~0.44 eV but not confirmed by CUORICINO Future experiments on neutrinoless double beta decay will allow to reach the sensitivity predicted by oscillations Their peculiar multiplinarity involves nuclear and e subnuclear physics , astrophysics , radioactivity, material science, geochronology etc