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 The dark side of double beta decay

Nuclear matrix elements F. Simkovic

Uncertainties F. Simkovic

Uncertainties F. Simkovic

Reminder 2  0 

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

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

M 0 calculations V. Rodin, A. Faessler, F. Simkovic, P. Vogel, nucl-th/ Looks convincing, but not everybody agrees... Remember: Half life to neutrino mass conversion is proportional to M 2 Consequence: We have to measure 3-4 isotopes to compensate for that

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? Answer: Show that neutrinos have a static magnetic momentt Energy in field: CPT changes sign of spin, thus E em =-E em, bu they must be thee same for Majorana neutrinos. Hence

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  or

Phase space   decay rate scales with Q 5  2  decay rate scales with Q 11 Q-value (keV) IsotopeNat. abund. (%) (PS 0v) –1 (yrs x eV 2 ) (PS 2v) –1 (yrs) Ca E242.52E16 Ge E257.66E18 Se E242.30E17 Zr E245.19E16 Mo E241.06E17 Pd E252.51E18 Cd E241.25E17 Sn E245.93E17 Te E242.08E17 Xe E242.07E17 Nd E248.41E15

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

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 * ME 2 * (m / m e ) 2 Measured quantity: Half-life Dependencies (BG limited) link to neutrino mass

Half - life estimate 0  T 1/2  a  (Mt/  EB) 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 N obs =  N BG  1/2 = ln2 a N A M t / N  (   T) Background  detector mass Q E Q+  E/2Q-  E/2 B

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)

The dominant problem - Background Cosmogenics thermal neutrons How to measure half-lives beyond 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 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 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  82 Se, 128,130 Te T. Kirsten et al, PRL 20 (1968) Disadvantage: You cannot discriminate 2  from 0 

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 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 Peak at 2039 keV Digital Pulse Shape Analysis Peak at 2039 keV

0 peak region SpectrumSpectrum

Latest HD-Moscow results Statistical significance: kg x yr Including pulse shape analysis: 35.5 kg x yr T 1/2 > 1.9 x yr (90% CL) (installed Nov. 95, only 4 detectors) m < 0.35 eV SSE

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/ C.A. Aalseth et al., hep-ex/ Reply H.V. Klapdor-Kleingrothaus, hep-ph/ H.L. Harney, hep-ph/ New evidence H.V. Klapdor-Kleingrothaus et al., Phys. Lett. B 586,198 (2004)

Heidelberg -Moscow H.V. Klapdor-Kleingrothaus et al, Phys. Lett. B 586, 198 (2004) T 1/2 = x yr m = eV Subgroup of collaboration more statistics Recalibration

The peak... 1.) Is there a peak? 2.) If it is real, is it something specific to Ge? Statistical treatment (Bayesian) 56 Co produced by cosmic rays (2034 keV photon+ 6 keV X-ray) 76 Ge(n,  ) 77 Ge (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)

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

CUORICINO-CUORE - Principle Thermal coupling Heat sink Thermometer Double beta decay Crystal absorber example: 750 g of TeO 10 mK C ~ T 3 (Debye)  C ~ 2×10 -9 J/K 1 MeV  -ray   T ~ 80  K   U ~10 eV

CUORICINO - Spectrum Gamma region Gamma region, dominated by gamma and beta events, highest gamma line = 2615 keV 208 Tl line (from 232 Th chain) 0 DBD Alpha region Alpha region, dominated by alpha peaks (internal or surface contaminations)

CUORICINO - Results 60 Co sum 208 Tl 130 Te DBD T 1/2 > 2.4 x yrs (90% CL) m < eV about 40 kg running

CUORICINO-CUORE Future: CUORE 760 kg TeO 2 approved 13x4 crystals/tower 19 towers

NEMO-3 Only approach with source different from detector

100 Mo kg Q  = 3034 keV  decay isotopes in NEMO-3 detector 82 Se kg Q  = 2995 keV 116 Cd 405 g Q  = 2805 keV 96 Zr 9.4 g Q  = 3350 keV 150 Nd 37.0 g Q  = 3367 keV Cu 621 g 48 Ca 7.0 g Q  = 4272 keV nat Te 491 g 130 Te 454 g Q  = 2529 keV  measurement External bkg measurement  search

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

100 Mo results (Data Feb – Dec. 2004) T 1/2 = 7.11  0.02 (stat)  0.54 (syst)  y 7.37 kg.y Cos(  ) Angular Distribution events 6914 g 389 days S/B = 40 NEMO Mo E 1 + E 2 (keV) Sum Energy Spectrum events 6914 g 389 days S/B = 40 NEMO Mo Background subtracted Data 2  2 Monte Carlo Data 2  2 Monte Carlo Background subtracted Idea: SuperNEMO (100 kg) T 1/2 > 5.8 x yrs (90% CL) R. Arnold et al, PRL 95 (2005) m < eV 2  : 0  :

SuperNEMO Top view Side view 5 m 1 m 4 m source tracker calorimeter Idea: Use 100 kg enriched 82 Se

COBRA Use large amount of CdZnTe Semiconductor Detectors Array of 1cm 3 CdTe detectors K. Zuber, Phys. Lett. B 519,1 (2001)

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

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 116 Cd above MeV

2  - decay S. Elliott, P. Vogel, Ann. Rev. Nucl. Part. Sci 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 Installed at LNGS about three month ago 4x4x4 detector array = 0.42 kg CdZnTe semiconductors

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

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

Pixellated detectors 3D - Pixelisation: Solid state TPC

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

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

Back of the envelope  1/2 = ln2 a N A M t / N  (   T) ( Background free)  50 meV implies half-life measurements of yrs 1 event/yr you need source atoms This is about 1000 moles of isotope, implying 100 kg Now you only can loose: nat. abundance, efficiency, background,...

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

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 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:

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....

Particle particle coupling g pp 1 + states contribution very sensitive to g pp (2  )

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

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