StAndrews 2006 lect2 orig

Contents: 

Contents Lecture 1 General introduction What is measured in DBD ? Neutrino oscillations and DBD Other BSM physics and DBD Nuclear matrix elements Lecture 2 Experimental considerations Current status of experiments Future activities Outlook and summary

Nuclear matrix elements: 

Nuclear matrix elements The dark side of double beta decay

Nuclear matrix elements: 

Nuclear matrix elements F. Simkovic

Uncertainties: 

Uncertainties F. Simkovic

Uncertainties: 

Uncertainties F. Simkovic

Reminder: 

Reminder 2 0

Multipoles: 

Multipoles 0: All intermediate states contribute How to explore those???

Charge exchange reactions: 

Charge exchange reactions Currently: (d,2He) and (3He,t) 2: Only intermediate 1+ states contribute Supportive measurements from accelerators

M0 calculations: 

M0 calculations V. Rodin, A. Faessler, F. Simkovic, P. Vogel, nucl-th/0503063 Looks convincing, but not everybody agrees... Remember: Half life to neutrino mass conversion is proportional to M2 Consequence: We have to measure 3-4 isotopes to compensate for that

Summary - So far: 

Summary - So far Neutrinoless double beta decay is the gold plated channel to probe the Majorana character of neutrinos It also provides information on the absolute neutrino mass scale Benchmark of 50 meV, hierarchies hard to disentangle, probably only way of laboratory experiment to go to 50 meV (ignoring claimed evidence) If observed, Schechter-Valle theorem guarantees Majorana neutrinos A lot of physics can be deduced not accessible to accelerators, but how to disentangle contributions to 0 However there are also major uncertainties, especially nuclear matrix elements We have achieved quite a lot, but there is still a lot to do

Can you prove that  is Dirac?: 

Can you prove that  is Dirac? Answer: Show that neutrinos have a static magnetic momentt Energy in field: CPT changes sign of spin, thus Eem=-Eem, bu they must be thee same for Majorana neutrinos. Hence

Contents: 

Contents Lecture 1 General introduction What is measured in DBD ? Neutrino oscillations and DBD Other BSM physics and DBD Nuclear matrix elements Lecture 2 Experimental considerations Current status of experiments Future activities Outlook and summary

The search for 0: 

The search for 0 or

Phase space : 

Phase space 0nbb decay rate scales with Q5 2nbb decay rate scales with Q11   Q-value (keV) Isotope Nat. abund. (%) (PS 0v)–1 (yrs x eV2) (PS 2v) –1 (yrs)

Slide15: 

Back of the envelope T1/2 = ln2 • a • NA• M • t / N (tT) ( Background free) For half-life measurements of 1024-25 yrs 1 event/yr you need 1024-25 source atoms This is about 10 moles of isotope, implying 1 kg Now you only can loose: nat. abundance, efficiency, background, ...

Spectral shapes: 

Spectral shapes Sum energy spectrum of both electrons 0: Peak at Q-value of nuclear transition T1/2  a •  (M•t/E•B)1/2 1 / T1/2 = PS * ME2 * (m / me)2 Measured quantity: Half-life Dependencies (BG limited) link to neutrino mass

Half - life estimate 0 : 

Half - life estimate 0 T1/2  a •  (M•t/E•B)1/2 a: isotopical abundance M: mass t: measuring time E: energy resolution B: background (c/keV/kg/yr) Signal sensitivity  stat. precision of background Nobs = NBG T1/2 = ln2 • a • NA• M • t / N (tT) Background  detector mass Q E Q+E/2 Q-E/2 B

Signal information: 

Signal information Single electron energies Daughter ion (A,Z+2) Angle between electrons Sum energy of both electrons Gamma rays (eg. four 511 keV photons in ++) (A,Z)  (A,Z+2) + 2 e- Signal: One new isotope (ionised), two electrons (fixed total energy)

Slide19: 

The dominant problem - Background Cosmogenics thermal neutrons How to measure half-lives beyond 1020 years??? The usual suspects (U, Th nat. decay chains) 2 Alphas, Betas, Gammas High energy neutrons from muon interactions The first thing you need is a mountain, mine,...

Contents: 

Contents Lecture 1 General introduction What is measured in DBD ? Neutrino oscillations and DBD Other BSM physics and DBD Nuclear matrix elements Lecture 2 Experimental considerations Current status of experiments Future activities Outlook and summary

Geochemical approach: 

Geochemical approach Major advantage: Experiment is running since a billion years T: age of ore Practically search has been possible due to the high sensitivity of noble gas mass spectrometry. Thus daughter should be noble gas. Signal: Isotopical anomaly  82Se, 128,130Te T. Kirsten et al, PRL 20 (1968) Disadvantage: You cannot discriminate 2 from 0

Experimental techniques: 

Experimental techniques Source = detector Source  detector Time projection chambers (TPC) Semiconductors Cryogenic bolometers Scintillators NEMO-3, SuperNEMO, DCBA, EXO Heidelberg-Moscow, IGEX, COBRA, GERDA, MAJORANA CUORICINO, CUORE SNO+, CANDLES, MOON, GSO, XMASS

Heidelberg -Moscow: 

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 Shape Analysis Peak at 2039 keV

Slide24: 

0 peak region Spectrum

Latest HD-Moscow results : 

Latest HD-Moscow results Statistical significance: 54.98 kg x yr Including pulse shape analysis: 35.5 kg x yr T1/2 > 1.9 x 1025 yr (90% CL) (installed Nov. 95, only 4 detectors) m < 0.35 eV SSE

Evidence for 0-decay?- References : 

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 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)

Heidelberg -Moscow: 

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

The peak...: 

The peak... 1.) Is there a peak? 2.) If it is real, is it something specific to Ge? Statistical treatment (Bayesian) 56Co produced by cosmic rays (2034 keV photon+ 6 keV X-ray) 76Ge(n,)77Ge (2038 keV photon) Some unknown line Inelastic neutron scattering (n,n‘) on lead Other suggestions, can be combination of all Note: We are talking about 1 event/year The easiest person to fool is yourself (R. Feynman)

Slide29: 

<m>=0.4eV V. Rodin et al., nucl-th/0503063, Nucl. Phys. A 2006 Uncertainties in nuclear matrix elements, example 116Cd  Check with a different isotope

CUORICINO-CUORE - Principle: 

CUORICINO-CUORE - Principle Thermal coupling example: 750 g of TeO2 @ 10 mK C ~ T 3 (Debye)  C ~ 2×10-9 J/K 1 MeV g-ray  DT ~ 80 mK  DU ~10 eV

CUORICINO - Spectrum: 

CUORICINO - Spectrum

CUORICINO - Results: 

CUORICINO - Results 60Co sum 208Tl 130Te DBD T1/2 > 2.4 x 1024 yrs (90% CL) m < 0.2-1.1 eV about 40 kg running

CUORICINO-CUORE: 

CUORICINO-CUORE Future: CUORE 760 kg TeO2 approved 13x4 crystals/tower 19 towers

NEMO-3: 

NEMO-3 Only approach with source different from detector

Slide35: 

100Mo 6.914 kg Qbb = 3034 keV bb decay isotopes in NEMO-3 detector 82Se 0.932 kg Qbb = 2995 keV 116Cd 405 g Qbb = 2805 keV 96Zr 9.4 g Qbb = 3350 keV 150Nd 37.0 g Qbb = 3367 keV Cu 621 g 48Ca 7.0 g Qbb = 4272 keV natTe 491 g 130Te 454 g Qbb = 2529 keV External bkg measurement

Slide36: 

NEMO-III - Event Typical 2 event of 100Mo

Slide37: 

100Mo results (Data Feb. 2003 – Dec. 2004) T1/2 = 7.11 ± 0.02 (stat) ± 0.54 (syst)  1018 y 7.37 kg.y Cos() Angular Distribution 219 000 events 6914 g 389 days S/B = 40 NEMO-3 100Mo E1 + E2 (keV) Sum Energy Spectrum 219 000 events 6914 g 389 days S/B = 40 NEMO-3 100Mo Idea: SuperNEMO (100 kg) T1/2 > 5.8 x 1023 yrs (90% CL) R. Arnold et al, PRL 95 (2005) m < 0.6 - 2.8 eV 2: 0:

SuperNEMO: 

SuperNEMO Idea: Use 100 kg enriched 82Se

COBRA: 

COBRA Use large amount of CdZnTe Semiconductor Detectors Array of 1cm3 CdTe detectors K. Zuber, Phys. Lett. B 519,1 (2001)

Isotopes : 

Isotopes nat. ab. (%) Q (keV) Decay mode

Advantages: 

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

2 - decay: 

2 - decay S. Elliott, P. Vogel, Ann. Rev. Nucl. Part. Sci. 2002 Energy resolution extremely important check whether people use FWHM or  (there is a factor 2.35 difference) Fraction of 2 in 0 peak: Signal/Background: 2 is ultimate, irreducible background

The first layer: 

The first layer Installed at LNGS about three month ago 4x4x4 detector array = 0.42 kg CdZnTe semiconductors

The solid state TPC: 

The solid state TPC Energy resolution Tracking Pixellated CdZnTe detectors Massive background Reduction (Particle-ID) Positive signal information

Pixellisation - I: 

Pixellisation - I Particle ID possible, 200m pixels (example simulations): eg. Could achieve nearly 100% identification of 214Bi events (214Bi  214Po  210Pb) . 0  1-1.5mm ~15m 3 MeV  7.7MeV  life-time = 164.3s Beta with endpoint 3.3MeV = 1 pixel,  and = several connected pixel, = some disconnected p.

Pixellated detectors: 

Pixellated detectors 3D - Pixelisation: Solid state TPC

Slide47: 

Nobody said it was going to be easy, and nobody was right George W. Bush

Contents: 

Contents Lecture 1 General introduction What is measured in DBD ? Neutrino oscillations and DBD Other BSM physics and DBD Nuclear matrix elements Lecture 2 Experimental considerations Current status of experiments Future activities Outlook and summary

Slide49: 

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, ...

Future projects, ideas: 

Future projects, ideas small scale ones will expand, very likely not a complete list... Status 2006

Future - Ge approaches: 

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), 35 kg enriched bought MERGE

EXO: 

EXO 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 New feature:

Summary : 

Summary To account for matrix element uncertainties and to disentangle the physics mechanism we need at least 3(4) isotopes measured 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

Hope....: 

Hope....

Particle particle coupling gpp: 

Particle particle coupling gpp 1+ states contribution very sensitive to gpp (2)

Fixing gpp: 

Fixing gpp Some tension in fixing to observed half-lives or ft-values 116Cd  116In  116Sn SSD ft-value supports gpp = 0.85

ft-values: 

ft-values Some existing data not that good, if available at all  new measurements at TRIUMF using ion traps