1 / 43

Neutrino masses from double beta decay

Neutrino masses from double beta decay. Kai Zuber University of Sussex. Contents. Introduction Double beta decay COBRA Outlook Summary and conclusions. Neutrino masses from cosmology. New WMAP measurement + SDSS data. Mass bound model dependent, currently done within  CDM.

deron
Download Presentation

Neutrino masses from double beta decay

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Neutrino masses from double beta decay Kai ZuberUniversity of Sussex UK Forum Dark Matter, RAL

  2. Contents • Introduction • Double beta decay • COBRA • Outlook • Summary and conclusions UK Forum Dark Matter, RAL

  3. Neutrino masses from cosmology New WMAP measurement + SDSS data Mass bound model dependent, currently done within CDM UK Forum Dark Matter, RAL

  4. Neutrinos in cosmology M. Tegmark UK Forum Dark Matter, RAL

  5. Combined SDSS and WMAP data M. Tegmark et al., Phys. Rev. D 69, 103501 (2003) UK Forum Dark Matter, RAL

  6. Neutrino mass from cosmology O. Lahav, Neutrino 2004 All upper limits 95% CL, but different assumed priors !

  7. Oscillation evidences LSND sin2 2 = 10-1-10-3 , m2 = 0.1-6 eV2 Atmospheric sin2 2 = 1.00 , m2 = 2.1  10-3 eV2 Solar + reactors sin2 2 = 0.81 , m2 = 8.2  10-5 eV2 If all three are correct... we need more (sterile ones) UK Forum Dark Matter, RAL

  8. Neutrino mass schemes UK Forum Dark Matter, RAL

  9. Neutrinos mass density UK Forum Dark Matter, RAL

  10. Contents • Introduction • Double beta decay • COBRA • Outlook • Summary and conclusions UK Forum Dark Matter, RAL

  11. 1+ (A,Z+1) (A,Z) 0+ (A,Z+2) Double beta decay - • (A,Z)  (A,Z+2) + 2 e- + 2e2 • (A,Z)  (A,Z+2) + 2 e-0 0+ In nature there are 35 isotopes 2: Seen in 10 isotopes, important for nuclear physics input 0: Only possible if neutrinos are Majorana particles UK Forum Dark Matter, RAL

  12. Spectral shapes 0: Peak at Q-value of nuclear transition Measured quantity: Half-life Dependencies (BG limited) T1/2  a •  (M•t/E•B)1/2 link to neutrino mass 1 / T1/2= PS * NME2 * (m / me)2 Sum energy spectrum of both electrons UK Forum Dark Matter, RAL

  13. 3 Flavour oscillations (PMNS) Analogous to CKM matrix solar atmospheric If sin 13 0 CP-violation Majorana: U= UPMNS diag(1,e i ,e i ) UK Forum Dark Matter, RAL

  14. Physical quantities Experimental observable: Half-life Double beta decay: Effective Majorana neutrino mass relative CP phases = 1 Beta decay me =  |Uek|2 mk UK Forum Dark Matter, RAL

  15. Neutrino mass schemes and DBD „normal“ mass hierarchy m1<m2<m3 „inverted“ mass hierarchy m3 < m1 < m2 almost degenerate neutrinos m1≈ m2≈ m3 quasi-degenerate hierarchical UK Forum Dark Matter, RAL

  16. Ca 48 4271 0.187 4.10E24 2.52E16 Ge 76 2039 7.8 4.09E25 7.66E18 Se 82 2995 9.2 9.27E24 2.30E17 Zr 96 3350 2.8 4.46E24 5.19E16 Mo 100 3034 9.6 5.70E24 1.06E17 Pd 110 2013 11.8 1.86E25 2.51E18 Cd 116 2809 7.5 5.28E24 1.25E17 Sn 124 2288 5.64 9.48E24 5.93E17 Te 130 2529 34.5 5.89E24 2.08E17 Xe 136 2479 8.9 5.52E24 2.07E17 Nd 150 3367 5.6 1.25E24 8.41E15 Phase space 0nbb decay rate scales with Q5 2nbb decay rate scales with Q11 Q-value (keV) (PS 0v)–1 (yrs) (PS 2v) –1 (yrs) Isotope Nat. abund. (%) UK Forum Dark Matter, RAL

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

  18. Spectrum 0 peak region UK Forum Dark Matter, RAL

  19. 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) UK Forum Dark Matter, RAL

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

  21. „Evidence“ II Step 1 Step 2 Some lines known, some are not Left hand side BG too high, hence for right hand side onlyregion without lines except the double beta one UK Forum Dark Matter, RAL For the double beta line they restrict themselves to 5 SD region

  22. Heidelberg-Moscow Evidence UK Forum Dark Matter, RAL

  23. Heidelberg -Moscow more statistics Recalibration Evidence ? T1/2 = 0.6 - 8.4 x 1025 yr Subgroup of collaboration m = 0.17 - 0.63 eV H.V. Klapdor-Kleingrothaus et al, Phys. Lett. B 586, 198 (2004) UK Forum Dark Matter, RAL

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

  25. DBD Q-value Running experiments CUORICINO: cryogenic bolometers40.7 kg TeO2 T1/2 > 1.8 x 1024 yr (90% CL) Arnaboldi et al, hep-ex/050134 NEMO-3: TPC Future: CUORE 760 kg TeO2 approved 10 kg enriched foils, 6 kg 100Mo T1/2 > 3.1 x 1023 yr (90% CL) Idea: Super-NEMO (100 kg) UK Forum Dark Matter, RAL

  26. C0BRA Use large amount of CdZnTe Semiconductor Detectors Array of 1cm3 CdTe detectors K. Zuber, Phys. Lett. B 519,1 (2001) UK Forum Dark Matter, RAL

  27. Isotopes nat. ab. (%) Q (keV) Decay mode UK Forum Dark Matter, RAL

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

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

  30. The 2x2 prototype Installation of setup at Gran Sasso Underground Laboratory 4 naked 1cm3 CdZnTe Very preliminary Cd113 0 region Cd116 0 region Te130 2.5 kg x days of data UK Forum Dark Matter, RAL

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

  32. The solid state TPC Introduce tracking properties by using segmented, Pixellated electrodes and pulse shape analysis Single electron spectra Angular correlation coefficient  UK Forum Dark Matter, RAL

  33. Pixellated detectors 3D - Pixelisation: UK Forum Dark Matter, RAL

  34. Contents • Introduction • Double beta decay • COBRA • Outlook • Summary and conclusions UK Forum Dark Matter, RAL

  35. 0nbb Experimental Situation 2 main experimental approaches: • Active Source • Passive Source Best 0n2b results involve active source experiments UK Forum Dark Matter, RAL

  36. Back of the envelope T1/2 = ln2 • a•NA• M • t / N (tT) ( Background free) 50 meV implies half-life measurements of 1026-27 yrs 1 event/yr you need 1026-27 source atoms This is about 1000 moles of isotope, implying 100 kg Now you only can loose: nat. abundance, efficiency, background, ... UK Forum Dark Matter, RAL

  37. 2 - decay 2 is ultimate, irreducible background Energy resolution important semiconductor Fraction of 2 in 0  peak: S. Elliott, P. Vogel, Ann. Rev. Nucl. Part. Sci. 2002 Signal/Background: UK Forum Dark Matter, RAL + Tracking option

  38. O.Cremonesi, n 2002 Future projects UK Forum Dark Matter, RAL * Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31

  39. Future - Ge approaches MAJORANA 500 kg of enrichedGe detectors GERDA Naked enriched Ge-crystals inLAr with lead shield Segmentation and pulse shape discrimination 20 kg enriched Ge-detectorsat hand (former HD-MO and IGEX) MERGE UK Forum Dark Matter, RAL

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

  41. ++ -modes n p e In general: Double charged higgs bosons, R-parity violating SUSY couplings, leptoquarks... e p n Q-4mec2 • (A,Z)  (A,Z-2) + 2 e+ (+2e)++ Q-2mec2 • e- + (A,Z)  (A,Z-2) + e+ (+2e )+/EC Q • 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) UK Forum Dark Matter, RAL

  42. Summary Double beta decay is the gold plated channel to probethe fundamental character of neutrinos Taking current evidences from oscillation data it islikely to be the only way to fix the absolute neutrino mass To go below 50 meV requires hundreds of kilograms ofenriched material However, there is a hotly discussed evidence by the Heidelberg group, which would imply almost degenerate neutrinos A lot of proposals and R&D projects among them is COBRA using CdZnTe semiconductors We need info on nuclear matrix elements ! UK Forum Dark Matter, RAL

  43. Join the Party! UK Forum Dark Matter, RAL

More Related