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StAndrews_2006_lect2_orig

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					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
       2: Only intermediate 1+ states contribute
Supportive measurements
from accelerators




                             Currently: (d,2He) and (3He,t)
       M0       calculations
V. Rodin, A. Faessler, F. Simkovic, P. Vogel, nucl-th/0503063



Remember: Half life to neutrino mass conversion
is proportional to M2

Consequence: We have to measure 3-4 isotopes
to compensate for that




 Looks convincing, but not everybody agrees...
                 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:    Eem     B  d   E
CPT changes sign of spin, thus Eem=-Eem, bu they must be thee
same for Majorana neutrinos. Hence   d  0
                                        
                    eL  ee e  eR 
                    
                   
                              e
                                         
                                       
                    eR      R 
                                       

                     3GF e              19 m 
                         m  3.2 10   B  
                  8 2  2
                                            eV 
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
             0decay rate scales with Q5

            2 decay rate scales with Q11
           Q-value Nat. abund. (PS 0v)–1       (PS 2v) –1
Isotope
            (keV)                  (yrs x eV2)   (yrs)
                      (%)
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    2802        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
             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
         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 * ME2 * (m / me)2

Sum energy spectrum of both electrons
       Half - life estimate 0
           T1/2 = ln2 • a • NA• M • t / N (tT)
Signal sensitivity  stat. precision of background Nobs = NBG
   Background  detector mass

              T1/2  a •  (M•t/E•B)1/2             N   BEMt
 • a: isotopical abundance        B
 • M: mass
 • t: measuring time                     
 • E: energy resolution
                                       Q-E/2 Q Q+E/2       E
 • B: background (c/keV/kg/yr)
                 Signal information
                 (A,Z)  (A,Z+2) + 2 e-
Signal: One new isotope (ionised), two electrons (fixed total energy)

       Single electron energies
      Angle between electrons
      Sum energy of both electrons
       Daughter ion (A,Z+2)
      Gamma rays (eg. four 511 keV photons in ++)
  The dominant problem - Background
   How to measure half-lives beyond 1020 years???


The first thing you need is a mountain, mine,...
     • The usual suspects (U, Th nat. decay chains)
     • Alphas, Betas, Gammas
     • Cosmogenics
     • thermal neutrons
     • High energy neutrons from muon interactions
     • 2
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
     Signal: Isotopical anomaly        N(Z  2, A) 1 T: age of ore
                                   
                                        N(Z, A) T

  Practically search has been possible due to the high sensitivity of
  noble gas mass spectrometry. Thus daughter should be noble gas.
                           



 82Se, 128,130Te                             Disadvantage:
                                              You cannot discriminate
                                              2 from 0
T. Kirsten et al, PRL 20 (1968)
       Experimental techniques
    Source = detector        Source  detector


   Semiconductors          Time projection chambers (TPC)
Heidelberg-Moscow, IGEX,      NEMO-3, SuperNEMO,
COBRA, GERDA, MAJORANA        DCBA, EXO
  Cryogenic bolometers
  CUORICINO, CUORE
      Scintillators
 SNO+, CANDLES, MOON,
 GSO, XMASS
                      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
0 peak region
t
r
c
e



u
p
S




m
     Latest HD-Moscow results
             Statistical significance: 54.98 kg x yr
         Including pulse shape analysis: 35.5 kg x yr
             (installed Nov. 95, only 4 detectors)




           SSE



T1/2 > 1.9 x 1025 yr (90% CL)                   m < 0.35 eV
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

more statistics

Recalibration




Subgroup of collaboration                                            m = 0.17 - 0.63 eV
                            T1/2 = 0.6 - 8.4 x 1025 yr

           H.V. Klapdor-Kleingrothaus et al, Phys. Lett. B 586, 198 (2004)
                           The peak...
  1.) Is there a peak?
   Statistical treatment (Bayesian)

 2.) If it is real, is it something specific to Ge?
 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)
     Check with a different isotope
Uncertainties in nuclear matrix elements, example 116Cd
                                                <m>=0.4eV




  V. Rodin et al., nucl-th/0503063, Nucl. Phys. A 2006
CUORICINO-CUORE - Principle
                      Heat sink


                   Thermal coupling
                     Thermometer
                   Double beta decay




Crystal absorber


                     example: 750 g of TeO2 @ 10 mK
                     C ~ T 3 (Debye)  C ~ 2×10-9 J/K
                     1 MeV -ray      T ~ 80 K
                                      U ~10 eV
      CUORICINO - Spectrum
          0DBD




Gamma region,
                       Alpha region, dominated by alpha peaks
dominated by gamma
and beta events,       (internal or surface contaminations)
highest gamma line =
2615 keV 208Tl line
(from 232Th chain)
       CUORICINO - Results
                                   about 40 kg running
                           208Tl
60Co   sum
             130Te   DBD
                                   T1/2 > 2.4 x 1024 yrs
                                   (90% CL)

                                   m < 0.2-1.1 eV
CUORICINO-CUORE
                         19 towers
   13x4 crystals/tower




  Future: CUORE 760 kg TeO2 approved
                NEMO-3
Only approach with source different from detector
                    decay isotopes in NEMO-3 detector

                                          2 measurement
                                              116Cd   405 g
                                                 Q= 2805 keV

                                              96Zr     9.4 g
                                                 Q= 3350 keV

                                              150Nd   37.0 g
                                                 Q= 3367 keV

                                              48Ca      7.0 g
                                                 Q= 4272 keV

                                              130Te    454 g
                                                 Q= 2529 keV
                                                                  External bkg
100Mo                  82Se                   natTe   491 g
         6.914 kg             0.932 kg                            measurement
  Q= 3034 keV         Q= 2995 keV
                                               Cu      621 g

             0 search
NEMO-III - Event
Typical 2 event of 100Mo
                                      100Mo      results
                                                                       7.37 kg.y
                                      (Data Feb. 2003 – Dec. 2004)

                  Sum Energy Spectrum                                  Angular Distribution

               NEMO-3              219 000 events                                     219 000 events
                                                                NEMO-3
                                           6914 g                                             6914 g
             100Mo                       389 days                    100Mo                  389 days
                                         S/B = 40                                           S/B = 40
                                                                          •   Data
                                                                              22
                                     •   Data                                 Monte Carlo
                                      22                                     Background
                                      Monte Carlo                              subtracted
                                        Background
                                        subtracted




                                    E1 + E2 (keV)                                              Cos()

               2: T1/2 = 7.11  0.02 (stat)  0.54 (syst)  1018 y
0: T1/2 > 5.8 x 1023 yrs (90% CL) m < 0.6 - 2.8 eV
  R. Arnold et al, PRL 95 (2005)                      Idea: SuperNEMO (100 kg)
         SuperNEMO
Idea: Use 100 kg enriched 82Se
              source
        tracker
  calorimeter



                       1m           4m




       5m
   Top view                 Side view
       COBRA

  Use large amount of
        CdZnTe
Semiconductor Detectors

                           Array of 1cm3
                           CdTe detectors



             K. Zuber, Phys. Lett. B 519,1 (2001)
             Isotopes
        nat. ab. (%) Q (keV)   Decay mode

Zn70        0.62     1001       ß-ß-
Cd114       28.7     534        ß-ß-
Cd116       7.5      2809       ß-ß-
Te128       31.7     868        ß-ß-
Te130       33.8     2529       ß-ß-
Zn64        48.6     1096       ß+/EC
Cd106       1.21     2771       ß+ß+
Cd108       0.9      231        EC/EC
Te120       0.1      1722       ß+/EC
                  Advantages
• Source = detector
• Semiconductor (Good energy resolution, clean)
• Room temperature (safety)
• Modular design (Coincidences)
• Two isotopes at once
• Industrial development of CdTe detectors
•   116Cd   above 2.614 MeV
• Tracking („Solid state TPC“)
                                        2 - decay
                    2 is ultimate, irreducible background
     Energy resolution extremely important
     check whether people use FWHM or  (there is a factor 2.35 difference)
                                  8Q(E /Q) 6
Fraction of 2 in 0 peak: F              3.7 *10 10
                                      me
 S. Elliott, P. Vogel, Ann. Rev. Nucl. Part. Sci. 2002


                                                                Signal/Background:
                                                                 S 1 T12
                                                                        /2
                                                                         0
                                                                              433
                                                                   B F T1/ 2
                                                         T12  3.2  10 19 yrs
                                                           /2


                                                         T10  2  10 26 yrs
                                                           /2
             The first layer
 4x4x4 detector array = 0.42 kg CdZnTe semiconductors




Installed at LNGS about three month ago
                  The solid state TPC
         Energy resolution            Tracking




• Massive background
Reduction (Particle-ID)
• Positive signal
information
                Pixellated CdZnTe detectors
                      Pixellisation - I
   • Particle ID possible, 200m pixels (example simulations):
= 1 pixel,  and = several connected pixel, = some disconnected p.

                                                     3 MeV 
                      0                                

                                                      ~15m

                    1-1.5mm


   • eg. Could achieve nearly 100% identification of 214Bi events
     (214Bi  214Po  210Pb)
                                 Beta with        7.7MeV 
   .                             endpoint         life-time =
                                   3.3MeV          164.3s
Pixellated detectors
    Solid state TPC

     3D - Pixelisation:
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

     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                        Status 2006




small scale ones will expand, very likely not a complete list...
           Future - Ge approaches
                       MAJORANA
                     500 kg of enriched
                     Ge detectors               GERDA

                                  Naked enriched Ge-crystals in
 Segmentation and                 LAr with lead shield
 pulse shape
 discrimination
                20 kg enriched Ge-detectors
                at hand (former HD-MO and
                IGEX), 35 kg enriched bought
MERGE
                          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
                  Summary
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
To go below 50 meV requires hundreds of kilograms of
enriched material
However, there is a hotly discussed evidence by the
Heidelberg group, which would imply almost degenerate
neutrinos
To account for matrix element uncertainties and to
disentangle the physics mechanism we need at least 3(4)
isotopes measured
Hope....
    Particle particle coupling gpp
1+ states contribution very sensitive to gpp (2)
                    Fixing gpp

                          SSD




                                ft-value supports gpp = 0.85

                            Some tension in fixing to observed
116Cd    116In  116Sn     half-lives or ft-values
              ft-values




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

				
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