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DOUBLE BETA DECAY

DOUBLE BETA DECAY. Ettore Fiorini, Tokio June 8, 2007. 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

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DOUBLE BETA DECAY

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  1. DOUBLE BETA DECAY Ettore Fiorini, Tokio June 8, 2007 • 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)

  2. The process • (A,Z) => (A,Z+2) + 2 e- + 2 n-e=> detected in ten nuclei • 2. (A,Z) => (A,Z+2) + 2 e- + c ( …2,3 c) => Majoron • 3. (A,Z) => (A,Z+2) + 2 e- => To be revealed by a pick => < mn >≠ 0

  3. - - e - e u e d n W e u W n e d W d u d W - e u 2n - bb decay n n e e 0n - bb decay Neutrinoless bb decay

  4. 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

  5. Double Beta –DisintegrationM.Goeppert-Mayer, The John Hopkins University(Received May, 20 , 1935)From the Fermi theory of b- 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 channel as a powerful way to search for lepton number non conservation. Presently it is also considered as the most powerful way to investigate the value of the mass of a Majorana neutrino

  6. Oscillations indicate Dm2 ≠ 0, but unable to determine <mn > M.Ramsey-Musolf This.Conf. M.Ramsey-Musolf This.Conf.

  7. What are we requesting to neutrinoless DBD?

  8. Also essential to detemine if n is aDirac or a Majorana Particle Majorana =>1937

  9. Phase space Nuclear matrix elements EffectiveMajorana neutrino mass rateof DDB-0n 1/t= G(Q,Z) |Mnucl|2 <mn>2 Nuclear matrix elementsact 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 neededQuasiparticle Random Phase Approximation (QRPA) ,renormalized RQRPA ( to incorporate the Pauli principle)and pnQRPA. Quite sensitive to the particle-particle interaction parameter g pp The rate of neutrinoless DBD

  10. Alice in the Wonderland Amicus Plato , sed magis amica veritasPlato is a friend, but truth even more Two approaches: V.A.Rodin et al Nucl.Phys.A 729 (2006) 107 => gppfrom Tbb2n J.Suhonen Phys.Lett. B 607 (2005) 87 => gppfrom Tb2n Very recently M.Kortelained & J.Suhonen 0705.0469 [nucl-th]“in Terra Infidelium” => calculation of NME for 76 Ge and82Se where no single beta decay exists => uses Tbb2n Replaces Jastrow short range correlation with Unitarity Correlation Operator Method => Quite larger NME than Rodin et al A.Faessler (letter) : Jastrow reduces 0.5±.1; Brueckner 0.65 ±.2; Unitarity Correlator Method (UCOM) 0.85 ±.1 , Deformation (150Nd maybe 76 Ge) So far ~ 20 different calculations => 6 chosen by V.M.Gehman & S.Elliott hep-ph/0701099

  11. Nuclear matrix elements 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

  12. Experimntal results *H.Ejiri, Journ.Phys.Soc.of Japan, 74 (2005) 2101

  13. 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

  14. In December 2001, 4 authors (KDHK) of the HM collaboration announce the discovery of neutrinoless DBD t1/20n(y) = (0.8 – 18.3)  1025 y (1  1025 y b.v.) Mbb= 0.05 - 0.84 eV (95% c.l.) 2004 2001 54.98 kg•y 2.2 s 71.7 kg•y 4 s better results in 2004 skepticism in DBD community in 2001 HM collaboration subset (KDHK): claim of evidence of 0n-DBD

  15. detector e- e- source e- e- detector SourceDetector Experimental approaches Geochemical experimentsi82Se = > 82Kr, 96Zr = > 96Mo (?) , 128Te = > 128Xe (non confirmed), 130Te = > 130TeRadiochemical experiments238U = > 238Pu (non confirmed) Direct experiments Source = detector (calorimetric) Sourcedetector

  16. heat bath Thermal sensor absorber crystal Incident particle Cryogenic detectors DE @ 5 keV ~100 mk ~ 1 mg<1 eV ~ 3 eV @ 2 MeV ~10 mk ~ 1 kg<10 eV ~ keV

  17. Other possible candidates for neutrinoless DBD 130Te has high transition energy and 34% isotopic abundance => enrichment non needed and/or very cheap. Any future extensions are possible Performance of CUORE, amply tested with CUORICINO

  18. Two new experimentsNEMO III and CUORICINO

  19. CUORICINO

  20. Search for the 2b|on in 130Te (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 2modules, 9detector each, crystal dimension3x3x6 cm3 crystal mass330 g 9 x 2 x 0.33 = 5.94 kg of TeO2 11modules, 4detector each, crystal dimension5x5x5 cm3 crystal mass790 g 4 x 11 x 0.79 = 34.76 kg of TeO2

  21. Present CUORICINO result (new) t >3 x 1024 (90 % c.l.) 11.8 kg year of 130Te <m0n> < .16 - .84 eV => Klapdor et al m0n < .1- .9 eV

  22. DBD and Neutrino Masses Present Cuoricino region Arnaboldi et al., submitted to PRL, hep-ex/0501034(2005). Possible evidence (best value 0.39 eV) H.V. Klapdor-Kleingrothaus et al., Nucl.Instrum.and Meth. ,522, 367 (2004). With the same matrix elements the Cuoricino limit is 0.53 eV “quasi” degeneracy m1 m2  m3 Inverse hierarchy m212= m2atm Direct hierarchy m212= m2sol Cosmological disfavoured region (WMAP) Feruglio F. , Strumia A. , Vissani F. hep-ph/0201291

  23. Next generation experiments B:bolometric, I:Ionization,S: Scintillation, T:Tracking

  24. Ionization P.Grabmayr: This Conf.

  25. IONIZATION COBRA Use large amount of CdZnTe Semiconductor Detectors

  26. CANDLES L.Ogawa: This Conf.

  27. Test <mn> = 0.150 eV Scintillation • 0n: 1000 events per • year with 1% natural • Nd-loaded liquid • scintillator in SNO++ simulation: one year of data maximum likelihood statistical test of the shape to extract 0n and 2n components…~240 units of Dc2 significance after only 1 year!

  28. Scintillation

  29. Tracking SUPERNEMO

  30. MOON An Option: Multilayer scintillator plates and thin MWPC tracking chambers with thin bb source film For M0n=3, E-resolution s~ 2.2 % forN ~ 5 ton year, <m> ~ 47 – 32 meV for 100Mo – 82Se 90 % CL Detector ≠bb source Select bb sources Solar n as well Tracking chamber • H. Ejiri, et al., PRL, 85, 2000. • H. Ejiri et al., Czech. J. Phsy. 54, .

  31. Pickup Anode 100 mV/div 100 ns/div Y Z X Gas:He(85%)+CO2(15%) Principle of DCBA(DriftChamberBeta-rayAnalyzer) 150Nd→150Sm+2e- p (MeV/c): momentum, r (cm): radius, : pitch angle,B (kG): magnetic field, me (MeV/c2): electron mass

  32. 2P1/2 650 nm 493 nm 4D3/2 metastable 47s 2S1/2 EXO Tracking • concept: scale Gotthard experiment adding Ba tagging to suppress background (136Xe136Ba+2e) • single Ba detected by optical spectroscopy • two options with 63% enriched Xe • High pressure Xe TPC • LXe TPC + scintillation • calorimetry + tracking • expected bkg only by -2 • energy resolution E = 2% Present 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 2n mode • Set decent limit for 0n mode (probe Heidelberg- Moscow) LXe TPC Full scale experiment at WIPP or SNOLAB • 10 t (for LXe ⇒ 3 m3) • b = 4×10-3 c/keV/ton/y • 1/21.3×1028 y in 5 years • 〈m〉 0.013 ÷ 0.037 eV

  33. CUORE Cryogenic Underground Observatory for Rare Events 80 cm 19 towers with 13 planes of 4 crystals each Array of 988 TeO2 detectors (750 g each) M = 741 kgof TeO2 = 203 kgof 130Te

  34. disfavoured by cosmology CUORE expected sensitivity In 5 years: Strumia A. and Vissani F. hep-ph/0503246

  35. CONCLUSIONS Neutrino oscillationsDm2 ≠0 <mn> finite for at least one neutrino Neutrinoless double beta decay would indicateif neutrino is alepton violatingMajorana 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

  36. DAMA results on bb decay modes Roma2,Roma1,LNGS,IHEP/Beijing + in some activities: INR-Kiev Experimental limits on T1/2 obtained by DAMA (red) and by previous experiments (blue) [limits at 90% C.L. except for 2b+0n in 136Ce and 2b-0n in 142Ce - 68% C.L.] …. and in progress

  37. 210Po a line Counts Energy [keV] Resolution of the 5x5x5 cm3 (~ 760 g ) crystals : 0.8 keV FWHM @ 46 keV 1.4 keV FWHM @ 0.351 MeV 2.1 keV FWHM @ 0.911 MeV 2.6 keV FWHM @ 2.615 MeV 3.2 keV FWHM @ 5.407 MeV (the best a spectrometer ever realized)

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