1 DOUBLE BETA DECAY • Double beta decay at the borderline between nuclear and subnuclear physics (no border in my opinion) • Nucleus acting as a microlaboratory to investigate fundamental problems in nuclear, subnuclear and astroparticle physics • Great need of help from theorist and experimentalist in volved in low energy nuclear physics • Double beta decay yesterday, today and tomorrow • Advanced instrumentation • Technical problems and particularly the reduction of the background (at the lowest value with respect to any other experiment) Ettore Fiorini, Tokio June 8, 2007
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1 DOUBLE BETA DECAY Double beta decay at the borderline between nuclear and subnuclear physics (no border in my opinion) Nucleus acting as a microlaboratory.
3 0 - decay e - e - d d u u W W e e Neutrinoless decay
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DOUBLE BETA DECAY
• Double beta decay at the borderline between nuclear and subnuclear physics (no border in my opinion)
• Nucleus acting as a microlaboratory to investigate fundamental problems in nuclear, subnuclear and astroparticle physics
• Great need of help from theorist and experimentalist in volved in low energy nuclear physics
• Double beta decay yesterday, today and tomorrow• Advanced instrumentation • Technical problems and particularly the reduction of the
background (at the lowest value with respect to any other experiment)
Ettore Fiorini, Tokio June 8, 2007
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1. (A,Z) => (A,Z+2) + 2 e- + 2 -e => detected in ten nuclei
2. 2. (A,Z) => (A,Z+2) + 2 e- + ( …2,3 ) => Majoron3. 3. (A,Z) => (A,Z+2) + 2 e- => To be revealed by a pick => < m >≠ 0
The process
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u e -
d
d
e -W
u
e
e
2 - decay
W
0 - decay
e -
e -
d
du
u
W
We
e
Neutrinoless decay
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Suggested in general form by Maria Goepper Mayer just one year after the Fermi theory of beta decay. She was interested in the nuclear point of view
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Double Beta –Disintegration
M.Goeppert-Mayer, The John Hopkins University(Received May, 20 , 1935)
From the Fermi theory of disintegration the probability of simultameous emission of two electrons (and two neutrinos) has been calculated. The result is that this process occurs sufficiently rarely to allow an half-life of over 1017 years for a nucleus, even if its isobar of atomic number different by 2 were more stable by 20 times the electron mass
Double beta decay was at the beginning searched In the neutrinoless Double beta decay was at the beginning searched In the neutrinoless channel as a powerful way to search for channel as a powerful way to search for lepton number non lepton number non conservationconservation. Presently it is also considered as the most powerful way . Presently it is also considered as the most powerful way to investigate the value of the to investigate the value of the massmass of a of a Majorana neutrinoMajorana neutrino
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Oscillations indicate m2 ≠ 0, but unable to determine <m >
M.Ramsey-Musolf This.Conf.
M.Ramsey-Musolf This.Conf.
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What are we requesting to neutrinoless DBD?
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Also essential to detemine if is a Dirac or a Majorana Particle
Majorana =>1937
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The rate of neutrinoless DBD
= G(Q,Z) |Mnucl|2 <m>2
rate of DDB-0 Phase space Nuclear matrix elements
EffectiveMajorana neutrino mass
Nuclear matrix elements act as the value of the effective neutrino massVarious models have been applied:
Shell Model ( valid for low A nuclei, but now ri-elaborated also for nuclei of intermediate A) . High speed computer facilities needed
Quasiparticle Random Phase Approximation (QRPA) ,renormalized RQRPA ( to incorporate the Pauli principle)and pnQRPA. Quite sensitive to the particle-particle interaction parameter g pp
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Alice in the Wonderland
Two approaches:
V.A.Rodin et al Nucl.Phys.A 729 (2006) 107 => gpp from T
J.Suhonen Phys.Lett. B 607 (2005) 87 => gpp from T
Very recently
M.Kortelained & J.Suhonen 0705.0469 [nucl-th] “in Terra Infidelium” => calculation of NME for 76 Ge and 82Se where no single beta decay exists => uses T
Replaces Jastrow short range correlation with Unitarity Correlation Operator Method => Quite larger NME than Rodin et al
1. S.Simkovic et al Phys.Rev. C 60 (1999) 055502 2. V.A.Rodin et al Nucl. Phys. A 766 (2006) 1073. O.Civitarese and J.Suhonen , Nucl. Phys. A 729 (2003) 8674.K.Muto et al , Z.Phys.334 (1989) 1875. E.Caurrier et al, Nucl. Phys. A 654 (1999) 973c6. P. Vogel , Presentation to CINPAP 2006
Conclusions of an experimentalist.=> many nuclei have to be investigated- Uncertaintiy on nuclear matrix elements- Environmenthal radioactivity produce many peaks which in principle could fake neutrinoles DBD events, but not in two or more different nuclei
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HM collaboration subset (KDHK): HM collaboration subset (KDHK): claim of evidence of 0claim of evidence of 0-DBD-DBD
In December 2001, 4 authors (KDHK) of the HM collaboration announce the discovery of neutrinoless DBD
/20 (y) = (0.8 – 18.3) 1025 y (1 1025 y b.v.)
M = 0.05 - 0.84 eV (95% c.l.)
54.98 kg•y 2.2
2001
71.7 kg•y 4
2004
skepticism in DBD community in 2001 better results in 2004
130Te has high transition energy and 34% isotopic abundance => enrichment non needed and/or very cheap. Any future extensions are possiblePerformance of CUORE, amply tested with CUORICINO
Other possible candidates for neutrinoless DBD Other possible candidates for neutrinoless DBD
Use large amount of CdZnTe Semiconductor Detectors
IONIZATION
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CANDLES
CaF2(pure)
liquid ScintillatorPMT(5")× 4
purewater
CaF2
LS
w.l. shifter
Reflector
L.Ogawa: This Conf.
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• 0n: 1000 events per• year with 1% natural• Nd-loaded liquid• scintillator in SNO++
Test <m> = 0.150 eV
maximum likelihood statistical test of the shape to extract 0 and 2 components…~240 units of 2 significance after only 1 year!
simulation:one year of data
Scintillation
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Scintillation
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Tracking SUPERNEMO
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MOONAn Option: Multilayer scintillator plates and thin MWPC tracking chambers with thin source filmFor , E-resolution 2.2 % forN ~ 5 ton year,
<m> ~ 47 – 32 meV for 100Mo – 82Se 90 % CL
Tracking chamber
H. Ejiri, et al., PRL, 85, 2000. H. Ejiri et al., Czech. J. Phsy. 54, .
Detector ≠ sourceSelect sourcesSolar as well
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Principle of DCBADCBA (DDrift CChamber BBeta-ray AAnalyzer)
Gas:He(85%)+CO2(15%)
Y
Z X
Pickup
100 mV/div 100 ns/div
Anode
ee mmpT
rBp
2/122 )(
,3.0cos150Nd→150Sm+2e-
p (MeV/c): momentum, r (cm): radius,
: pitch angle, B (kG): magnetic field,
me (MeV/c2): electron mass
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■ conceptconcept: scale Gotthard experiment adding Ba taggingBa tagging to suppress background (136Xe136Ba+2e)
■ single Ba detected by optical spectroscopy
■ two options with 63% enriched Xe ▶High pressure Xe TPC High pressure Xe TPC ▶LXe TPC + scintillation LXe TPC + scintillation
■ calorimetry + trackingcalorimetry + tracking■ expected bkg only by -2
▶energy resolution E = 2%
Present R&DPresent R&D■ Ba+ spectroscopy in HP Xe / Ba+ extr. ■ energy resolution in LXe (ion.+scint.)■ Prototype scale:► 200 kg enriched L136Xe without tagging► all EXO functionality except Ba id► operate in WIPP for ~two years ■Protorype goals:►Test all technical aspects of EXO
(except Ba id)►Measure 2 mode►Set decent limit for 0 mode
(probe Heidelberg- Moscow)
22PP1/21/2
44DD3/23/222SS1/21/2
493 nm493 nm650 nm650 nm
metastable metastable 47s47s
LXe TPCLXe TPC
EXOEXO
Full scale experiment at WIPP or Full scale experiment at WIPP or SNOLABSNOLAB■10 t10 t (for LXe ⇒ 3 m3)
▶b = 4×10-3 c/keV/ton/y▶1/21/2 1.31.3××10102828 y y in 5 years▶⟨⟨mm 0.013 0.013 ÷÷ 0.037 eV 0.037 eV
Tracking
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80 cm
19 towers with13 planes of4 crystals each
CUORECUORECryogenic Underground Observatory for Rare EventsCryogenic Underground Observatory for Rare Events
Neutrino oscillations m2 ≠0 <m> finite for at least one neutrino
Neutrinoless double beta decay would indicate if neutrino is a lepton violating Majorana particle and would allow in this case to determine <mn> and the hierachy of oscillations.
This process has been indicated by an experiment (Klapdor) with a value of ~0.44 eV but has not been confirmed
Future experiments on neutrinoless double beta decay will allow to reach the sensitivity predicted by oscillations in the inverse hierarchy scheme
Help us from low energy nuclear physics both with theory and experiments
The multidisciplinarity of searches on double beta decay involves nuclear and e subnuclear physics, astrophysics , radioactivity, material science, geochronology etc. It could help in explaining the particle-antiparticle asymmetry of the Universe
CONCLUSIONS
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DAMA results on DAMA results on decay modes decay modes
Experimental limits on T1/2 obtained by DAMA (red) and by previous experiments (blue) [limits at 90% C.L. except for 2+0 in 136Ce and 2-0 in 142Ce - 68% C.L.]