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
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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.
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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
UncertaintiesF. Simkovic
UncertaintiesF. Simkovic
Reminder
2 0
Multipoles0: All intermediate states contribute
How to explore those???
Charge exchange reactions
Currently: (d,2He) and (3He,t)
2: Only intermediate 1+ states contributeSupportive measurementsfrom accelerators
M0 calculationsV. 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 isotopesto 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
E em B d EEnergy in field:
CPT changes sign of spin, thus Eem=-Eem, bu they must be theesame for Majorana neutrinos. Hence
1/2 = ln2 • a • NA• M • t / N (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
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
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
1/2 = ln2 • a • NA• M • t / N (T)
Background Background detector mass detector mass
Q EQ+E/2Q-E/2
B
N BEMt
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 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
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 approachMajor advantage: Experiment is running since a billion years
N(Z 2, A)
N(Z, A)
1
TT: age of ore
Practically search has been possible due to the high sensitivity ofnoble 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 discriminate2 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 isotopically enriched ( 86%) in 7676Ge Ge • Lead box and nitrogen flushing ofLead box and nitrogen flushing of the detectors the detectors • Digital Pulse ShapeDigital Pulse Shape Analysis Analysis Peak at 2039 keVPeak at 2039 keV
0 p
eak
regi
on
Spectrum
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 Latest Heidelberg-Moscow results
H.V. Klapdor-Kleingrothaus et al., Eur. Phys. J. A 12,147 (2001)
EvidenceH.V. Klapdor-Kleingrothaus et al., Mod. Phys. Lett. A 16,2409 (2001)
Critical commentsF. Feruglio et al., hep-ph/0201291
C.A. Aalseth et al., hep-ex/0202018
ReplyH.V. Klapdor-Kleingrothaus, hep-ph/0205228
H.L. Harney, hep-ph/0205293
New evidenceH.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)
T1/2 = 0.6 - 8.4 x 1025 yr m = 0.17 - 0.63 eVSubgroup 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)
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)
<m>=0.4eV
V. Rodin et alV. Rodin et al., nucl-th/0503063, Nucl. Phys. A nucl-th/0503063, Nucl. Phys. A 20062006
Uncertainties in nuclear matrix elements, example 116Cd
Check with a different isotope
CUORICINO-CUORE - Principle
Thermal coupling
Heat sink
Thermometer
Double beta decay
Crystal absorber
example: 750 g of TeO2 @ 10 mK
C ~ T 3 (Debye) C ~ 2×10-9 J/K1 MeV -ray T ~ 80 K
U ~10 eV
CUORICINO - Spectrum
Gamma regionGamma region, dominated by gamma and beta events, highest gamma line = 2615 keV 208Tl line (from 232Th chain)
0DBD
Alpha regionAlpha region, dominated by alpha peaks
(internal or surface contaminations)
CUORICINO - Results
60Co sum208Tl
130Te DBD
T1/2 > 2.4 x 1024 yrs (90% CL)
m < 0.2-1.1 eV
about 40 kg running
CUORICINO-CUORE
Future: CUORE 760 kg TeO2 approved
13x4 crystals/tower19 towers
NEMO-3Only approach with source different from detector
100Mo 6.914 kg Q= 3034 keV
decay isotopes in NEMO-3 detector
82Se 0.932 kg Q= 2995 keV
116Cd 405 g Q= 2805 keV
96Zr 9.4 g Q= 3350 keV
150Nd 37.0 g Q= 3367 keV
Cu 621 g
48Ca 7.0 g Q= 4272 keV
natTe 491 g
130Te 454 g Q= 2529 keV
measurement
External bkg measurement
search
NEMO-III - EventTypical 2 event of 100Mo
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 events6914 g
389 daysS/B = 40
NEMO-3
100Mo
E1 + E2 (keV)
Sum Energy Spectrum
219 000 events6914 g
389 daysS/B = 40
NEMO-3
100Mo
Background subtracted
• Data22 Monte Carlo
• Data22 Monte CarloBackground subtracted
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 eV2:
0:
SuperNEMO
Top view Side view
5 m
1 m 4 m
sourcetracker
calorimeter
Idea: Use 100 kg enriched 82Se
COBRA
Use large amount of CdZnTe Semiconductor Detectors