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

d 0

eL

eR

ee e

e

eR

R

3GFe

8 2 2m 3.210 19 m

eV

B

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 0or

Phase space decay rate scales with Q5

2 decay rate scales with Q11

 

Q-value (keV)

Isotope Nat. abund. (%)

(PS 0v)–1 (yrs x eV2)

(PS 2v) –1 (yrs)

Ca 48 4271 0.187 4.10E24 2.52E16Ge 76 2039 7.8 4.09E25 7.66E18Se 82 2995 9.2 9.27E24 2.30E17Zr 96 3350 2.8 4.46E24 5.19E16Mo 100 3034 9.6 5.70E24 1.06E17Pd 110 2013 11.8 1.86E25 2.51E18Cd 116 2802 7.5 5.28E24 1.25E17Sn 124 2288 5.64 9.48E24 5.93E17Te 130 2529 34.5 5.89E24 2.08E17Xe 136 2479 8.9 5.52E24 2.07E17Nd 150 3367 5.6 1.25E24 8.41E15

Back of the envelope

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

Array of 1cm3

CdTe detectors

K. Zuber, Phys. Lett. B 519,1 (2001)

Isotopes

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+/ECCd106 1.21 2771 ß+ß+Cd108 0.9 231 EC/ECTe120 0.1 1722 ß+/EC

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

• 116Cd above 2.614 MeV

2 - decay

F 8Q(E /Q)6

me

3.7*10 10

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:

4331

02/1

22/1

T

T

FB

S

yrsT 1922/1 102.3

yrsT 2602/1 102

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 TPCEnergy resolution Tracking

Pixellated CdZnTe detectors

• Massive backgroundReduction (Particle-ID)• Positive signal information

Pixellisation - I• Particle ID possible, 200m pixels (example simulations):

• eg. Could achieve nearly 100% identification of 214Bi events (214Bi 214Po 210Pb)

.

00

1-1.5mm1-1.5mm

~15~15mm

3 MeV 3 MeV

7.7MeV life-time = 164.3s

Beta withendpoint 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 • NA• M • t / N (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

small scale ones will expand, very likely not a complete list...

Status 2006

Future - Ge approachesMAJORANA

GERDA

500 kg of enrichedGe detectors

Segmentation and pulse shape discrimination

Naked enriched Ge-crystals inLAr with lead shield

20 kg enriched Ge-detectorsat hand (former HD-MO andIGEX), 35 kg enriched bought

MERGE

EXOTracking and scintillation

136136Xe Xe 136136BaBa++++ e e-- e e- - final final state can be identified state can be identified

using optical spectroscopy using optical spectroscopy (M.Moe PRC44 (1991) 931)(M.Moe PRC44 (1991) 931)

200 kg enriched Xe prototype under construction at WIPP

New feature:

Summary

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

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

However, there is a hotly discussed evidence by the Heidelberg group, which would imply almost degenerateneutrinos

To go below 50 meV requires hundreds of kilograms ofenriched material

Hope....

Particle particle coupling gpp1+ states contribution very sensitive to gpp (2)

Fixing gpp

Some tension in fixing to observed half-lives or ft-values116Cd 116In 116Sn

SSD

ft-value supports gpp = 0.85

ft-values

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