2. 14-15. May 2005UK Forum Dark Matter, RAL Neutrino masses from double beta decay Kai Zuber University of Sussex

3. 14-15. May 2005UK Forum Dark Matter, RAL Contents Introduction Double beta decay COBRA Outlook Summary and conclusions

4. 14-15. May 2005UK Forum Dark Matter, RAL Neutrino masses from cosmology New WMAP measurement + SDSS data Mass bound model dependent, currently done within CDM

5. 14-15. May 2005UK Forum Dark Matter, RAL Neutrinos in cosmology M. Tegmark

6. 14-15. May 2005UK Forum Dark Matter, RAL Combined SDSS and WMAP data M. Tegmark et al., Phys. Rev. D 69, 103501 (2003)

7. Neutrino mass from cosmology DataAuthors m m i 2dFGRSElgaroy et al. 02 < 1.8 eV WMAP+2dF+…Spergel et al. 03 < 0.7 eV WMAP+2dFHannestad 03 < 1.0 eV SDSS+WMAPTegmark et al. 04 < 1.7 eV WMAP+2dF+ SDSS Crotty et al. 04 < 1.0 eV Clusters +WMAPAllen et al. 040.56 +0.30 -0.26 eV All upper limits 95% CL, but different assumed priors ! O. Lahav, Neutrino 2004

8. 14-15. May 2005UK Forum Dark Matter, RAL Oscillation evidences LSND Atmospheric Solar + reactors sin 2 2 = 10 -1 -10 -3, m 2 = 0.1-6 eV 2 sin 2 2 = 1.00, m 2 = 2.1 10 -3 eV 2 sin 2 2 = 0.81, m 2 = 8.2 10 -5 eV 2 If all three are correct... we need more (sterile ones)

9. 14-15. May 2005UK Forum Dark Matter, RAL Neutrino mass schemes

10. 14-15. May 2005UK Forum Dark Matter, RAL Neutrinos mass density

11. 14-15. May 2005UK Forum Dark Matter, RAL Contents Introduction Double beta decay COBRA Outlook Summary and conclusions

12. 14-15. May 2005UK Forum Dark Matter, RAL (A,Z) (A,Z+2) + 2 e - + 2 e 2 (A,Z) (A,Z+2) + 2 e - 0 - 0+0+ 1+1+ 0+0+ (A,Z) (A,Z+1) (A,Z+2) 0 : Only possible if neutrinos are Majorana particles In nature there are 35 isotopes Double beta decay 2 : Seen in 10 isotopes, important for nuclear physics input

13. 14-15. May 2005UK Forum Dark Matter, RAL Spectral shapes Sum energy spectrum of both electrons 0 : Peak at Q-value of nuclear transition T 1/2 a (Mt/ EB) 1/2 1 / T 1/2 = PS * NME 2 * (m / m e ) 2 Measured quantity: Half-life Dependencies (BG limited) link to neutrino mass

14. 14-15. May 2005UK Forum Dark Matter, RAL 3 Flavour oscillations (PMNS) Analogous to CKM matrix solar If sin 13 0 CP-violation atmospheric U= U PMNS diag(1,e i,e i )Majorana:

15. 14-15. May 2005UK Forum Dark Matter, RAL Physical quantities Experimental observable: Half-life Double beta decay: Effective Majorana neutrino mass Beta decay m e = |U ek | 2 m k relative CP phases = 1

16. 14-15. May 2005UK Forum Dark Matter, RAL inverted mass hierarchy m 3 < m 1 < m 2 hierarchical quasi-degenerate Neutrino mass schemes and DBD normal mass hierarchy m 1 <m 2 <m 3 almost degenerate neutrinos m 1 m 2 m 3

17. 14-15. May 2005UK Forum Dark Matter, RAL Phase space decay rate scales with Q 5 2 decay rate scales with Q 11 Q-value (keV) IsotopeNat. abund. (%) (PS 0v) –1 (yrs) (PS 2v) –1 (yrs) Ca 4842710.1874.10E242.52E16 Ge 7620397.84.09E257.66E18 Se 8229959.29.27E242.30E17 Zr 9633502.84.46E245.19E16 Mo 10030349.65.70E241.06E17 Pd 110201311.81.86E252.51E18 Cd 11628097.55.28E241.25E17 Sn 12422885.649.48E245.93E17 Te 130252934.55.89E242.08E17 Xe 13624798.95.52E242.07E17 Nd 15033675.61.25E248.41E15

18. 14-15. May 2005UK Forum Dark Matter, RAL Heidelberg -Moscow Five Ge diodes (overall mass 10.9 kg) Five Ge diodes (overall mass 10.9 kg) isotopically enriched ( 86%) in 76 Ge isotopically enriched ( 86%) in 76 Ge Lead box and nitrogen flushing of the detectors Lead box and nitrogen flushing of the detectors Digital Pulse Shape Analysis (factor 5 reduction) Peak at 2039 keV Digital Pulse Shape Analysis (factor 5 reduction) Peak at 2039 keV

19. 14-15. May 2005UK Forum Dark Matter, RAL 0 peak region SpectrumSpectrum

20. 14-15. May 2005UK Forum Dark Matter, RAL Evidence for 0 -decay?- References Latest Heidelberg-Moscow results H.V. Klapdor-Kleingrothaus et al., Eur. Phys. J. A 12,147 (2001) Evidence H.V. Klapdor-Kleingrothaus et al., Mod. Phys. Lett. A 16,2409 (2001) Critical comments F. Feruglio et al., hep-ph/0201291 C.A. Aalseth et al., hep-ex/0202018 and more Reply H.V. Klapdor-Kleingrothaus, hep-ph/0205228 H.L. Harney, hep-ph/0205293 New evidence H.V. Klapdor-Kleingrothaus et al, Phys. Lett. B 586, 198 (2004)

21. 14-15. May 2005UK Forum Dark Matter, RAL Evidence I Statistical significance: 53.93 kg x yr Apply pulse shape 28 kg x yr Ignore det. 4 (no muon veto, slightly worse energy resolution) Completely new statistical treatment - Bayesian method Only region of 5 around peak is used for background determination Step 1 Step 2

22. 14-15. May 2005UK Forum Dark Matter, RAL Evidence II Step 1Step 2 For the double beta line they restrict themselves to 5 SD region Left hand side BG too high, hence for right hand side only region without lines except the double beta one Some lines known, some are not

23. 14-15. May 2005UK Forum Dark Matter, RAL Heidelberg-Moscow Evidence

24. 14-15. May 2005UK Forum Dark Matter, RAL Heidelberg -Moscow Evidence ? H.V. Klapdor-Kleingrothaus et al, Phys. Lett. B 586, 198 (2004) T 1/2 = 0.6 - 8.4 x 10 25 yr m = 0.17 - 0.63 eV Subgroup of collaboration more statistics Recalibration

25. 14-15. May 2005UK Forum Dark Matter, RAL If peak is real... Is peak something specific to Ge? Uncertainties in the nuclear matrix elements? Check with a different isotope Physics mechanism at work ? Tracking 1.) Go out and check (GERDA, MAJORANA) 2.) NEMO, COBRA n n p p e e

26. 14-15. May 2005UK Forum Dark Matter, RAL Running experiments DBD Q-value CUORICINO: cryogenic bolometers 40.7 kg TeO 2 Future: CUORE 760 kg TeO 2 approved NEMO-3: TPC 10 kg enriched foils, 6 kg 100 Mo Idea: Super-NEMO (100 kg) T 1/2 > 1.8 x 10 24 yr (90% CL) Arnaboldi et al, hep-ex/050134 T 1/2 > 3.1 x 10 23 yr (90% CL)

27. 14-15. May 2005UK Forum Dark Matter, RAL C0BRA Use large amount of CdZnTe Semiconductor Detectors Array of 1cm 3 CdTe detectors K. Zuber, Phys. Lett. B 519,1 (2001)

28. 14-15. May 2005UK Forum Dark Matter, RAL Isotopes nat. ab. (%)Q (keV)Decay mode

29. 14-15. May 2005UK Forum Dark Matter, RAL Advantages Source = detector Semiconductor (Good energy resolution, clean) Room temperature (safety) Tracking (Solid state TPC) Modular design (Coincidences) Industrial development of CdZnTe detectors Two isotopes at once 116 Cd above 2.614 MeV

30. 14-15. May 2005UK Forum Dark Matter, RAL Cobra - The people T. Leigertwood, D. McKechan, C. Reeve, J. Wilson, K. Zuber C. Gößling, H. Kiel, D. Münstermann, S. Oehl, T. Villett University of Dortmund University of Sussex Laboratori Nazionali del Gran Sasso M. Junker University of Warwick P.F. Harrison, B. Morgan, Y. Ramachers, D. Stewart T. Bloxham, M. Freer P. Seller B. Fulton, R. Wadsworth A. Boston, P. Booth, P. Nolan University of Birmingham University of Liverpool University of York Rutherford Appleton Laboratory

31. 14-15. May 2005UK Forum Dark Matter, RAL The 2x2 prototype 4 naked 1cm 3 CdZnTe Very preliminary 2.5 kg x days of data 0 region Te130 0 region Cd116 Installation of setup at Gran Sasso Underground Laboratory Cd113

32. 14-15. May 2005UK Forum Dark Matter, RAL The 64 detector array Aim for next 2 years: The next step towards a large scale experiment, Scalable modular design, explore coincidences Include: Cooling Nitrogen flushing Mass factor 16 higher, about 0.4 kg CdZnTe Physics: - Can access 2 ECEC in theoretically predicted region -Precision measurement of 113Cd - New limits Part of the detectors at Dortmund

33. 14-15. May 2005UK Forum Dark Matter, RAL The solid state TPC Single electron spectra Angular correlation coefficient Introduce tracking properties by using segmented, Pixellated electrodes and pulse shape analysis

34. 14-15. May 2005UK Forum Dark Matter, RAL Pixellated detectors 3D - Pixelisation:

35. 14-15. May 2005UK Forum Dark Matter, RAL Contents Introduction Double beta decay COBRA Outlook Summary and conclusions

36. 14-15. May 2005UK Forum Dark Matter, RAL 0 Experimental Situation ExperimentIsotopeT 1/2 0 (y) (eV) You Ke et al. 1998 48 Ca > 9.5 10 21 (76%) < 8.3 Klapdor-Kleingrothaus 2001 76 Ge > 1.9 10 25 < 0.35 Aalseth et al 2002 > 1.57 10 25 < 0.33 - 1.35 Arnold et al. 2004 82 Se> 1.3 x 10 23 < 1.5-3.1 Arnold et al. 2004 100 Mo >3.1 10 23 < 0.33-0.84 Danevich et al. 2000 116 Cd > 1 10 23 < 2.2 Bernatowicz et al. 1993 130/128 Te* (3.52 0.11) 10 -4 < 1.1 – 1.5 Bernatowicz et al. 1993 128 Te* > 7.7 10 24 < 1.1 – 1.5 Arnaboldi et al. 2005 130 Te > 1.8 10 24 < 0.5 – 1.1 Luescher et al. 1998 136 Xe > 4.4 10 23 < 1.8 – 5.2 Belli et al. 2001 136 Xe > 7 10 23 < 1.4 – 4.1 De Silva et al. 1997 150 Nd > 1.2 10 21 < 3 Danevich et al. 2001 160 Gd > 1.3 10 21 < 26 2 main experimental approaches : Active Source Active Source Passive Source Passive Source Best 0 2 results involve active source experiments

37. 14-15. May 2005UK Forum Dark Matter, RAL Back of the envelope 1/2 = ln2 a N A M t / N ( T) ( Background free) 50 meV implies half-life measurements of 10 26-27 yrs 1 event/yr you need 10 26-27 source atoms This is about 1000 moles of isotope, implying 100 kg Now you only can loose: nat. abundance, efficiency, background,...

38. 14-15. May 2005UK Forum Dark Matter, RAL 2 - decay + Tracking option S. Elliott, P. Vogel, Ann. Rev. Nucl. Part. Sci. 2002 Energy resolution important semiconductor Fraction of 2 in 0 peak: Signal/Background: 2 is ultimate, irreducible background

39. 14-15. May 2005UK Forum Dark Matter, RAL Future projects ExperimentAuthorIsotopeDetector descriptionT 5y 1/2 (y) * COBRA Zuber 2001 116 Cd 10 kg CdTe semiconductors 1 x 10 24 0.71 CUORICINO Arnaboldi et al 2001 130 Te 40 kg of TeO 2 bolometers 1.5 x 10 25 0.19 NEMO3 Sarazin et al 2000 100 Mo 10 kg of bb(0n) isotopes (7 kg Mo) with tracking 4 x 10 24 0.56 CUORE Arnaboldi et al. 2001 130 Te 760 kg of TeO 2 bolometers 7 x 10 26 0.027 EXO Danevich et al 2000 136 Xe 1 t enriched Xe TPC 8 x 10 26 0.052 GEM Zdesenko et al 2001 76 Ge 1 t enriched Ge diodes in liquid nitrogen + water shield 7 x 10 27 0.018 GENIUS Klapdor- Kleingrothaus et al 2001 76 Ge 1 t enriched Ge diodes in liquid nitrogen 1 x 10 28 0.015 MAJORANA Aalseth et al 2002 76 Ge 0.5 t enriched Ge segmented diodes 4 x 10 27 0.025 DCBA Ishihara et al 2000 150 Nd 20 kg enriched Nd layers with tracking 2 x 10 25 0.035 CAMEO Bellini et al 2001 116 Cd 1 t CdWO 4 crystals in liquid scintillator > 10 26 0.069 CANDLES Kishimoto et al 48 Ca several tons of CaF 2 crystal in liquid scintillator 1 x 10 26 GSO Danevich 2001 160 Gd 2 t Gd 2 SiO 5 :Ce cristal scintillator in liquid scintillator 2 x 10 26 0.065 MOON Ejiri et al 2000 100 Mo 34 t natural Mo sheets between plastic scintillator 1 x 10 27 0.036 Xe Caccianiga et al 2001 136 Xe 1.56 t of enriched Xe in liquid scintillator 5 x 10 26 0.066 XMASS Moriyama et al 2001 136 Xe 10 t of liquid Xe 3 x 10 26 0.086 * Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31 O.Cremonesi, 2002

40. 14-15. May 2005UK Forum Dark Matter, RAL Future - Ge approaches MAJORANA GERDA 500 kg of enriched Ge detectors Segmentation and pulse shape discrimination Naked enriched Ge-crystals in LAr with lead shield 20 kg enriched Ge-detectors at hand (former HD-MO and IGEX) MERGE

41. 14-15. May 2005UK Forum Dark Matter, RAL EXO Tracking and scintillation 136 Xe 136 Ba ++ e - e - final state can be identified using optical spectroscopy (M.Moe PRC44 (1991) 931) 200 kg enriched Xe prototype under construction at WIPP New feature:

42. 14-15. May 2005UK Forum Dark Matter, RAL + + - modes (A,Z) (A,Z-2) + 2 e + (+2 e ) + + e - + (A,Z) (A,Z-2) + e + (+2 e ) +/EC 2 e - + (A,Z) (A,Z-2) (+2 e ) EC/EC Important to reveal mechanism if 0 is discovered Enhanced sensitivity to right handed weak currents (V+A) n n p p e e In general: Q-4m e c 2 Q-2m e c 2 Q Double charged higgs bosons, R-parity violating SUSY couplings, leptoquarks...

43. 14-15. May 2005UK Forum Dark Matter, RAL Summary A lot of proposals and R&D projects among them is COBRA using CdZnTe semiconductors Double beta decay is the gold plated channel to probe the fundamental character of neutrinos Taking current evidences from oscillation data it is likely to be the only way to fix the absolute neutrino mass However, there is a hotly discussed evidence by the Heidelberg group, which would imply almost degenerate neutrinos To go below 50 meV requires hundreds of kilograms of enriched material

44. 14-15. May 2005UK Forum Dark Matter, RAL