Jenny Thomas

Double Beta Decay Present and Future

Jenny ThomasRencontres du Vietnam,

2004

J.Thomas, UCL

PreviewIntroduction: why search for 0 decay?Status of the search today: 3 experiments

CuoricinoNEMO-III Heidleberg-Moscow : signal!

Look at parameter space for 0experimentsHighlights of a few experiments on the horizonConclusions

J.Thomas, UCL

Introduction: oscillations

mLMA2 5x10 5eV 2 (7 meV)2

matm2 3x10 3 eV 2 (55 meV)2

12 13 13 12 13 1

23 12 12 13 23 12 23 12 13 23 13 23 2

23 12 12 23 13 12 23 23 12 13 13 23 3

e

i i

i i

c c c s s

c s e c s s c c e s s s c s

s s e c c s c s e c s s c c

J.Thomas, UCL

Introduction:oscillations

mmin ~ 0 - 0.01 eV

mmin ~ 0.03 - 0.06 eV

J.Thomas, UCL

Introduction:double beta decay

Large number of even-even nuclei undergo double-beta decay, but not single-beta decayStandard Model process of 2 is also allowed of courseEnrichment procedure in place for about 10 isotopesYou do not search for peaks in unknown places: you always know where to lookQ value of the decay is well known (difference in energy between two isotopes)

2+

0+

0+

0+

2-

Ge76

As76

Se76

e

e

e

e

n

n n

np

p

p

p

2 0

J.Thomas, UCL

Introduction:double beta decay

2.01.51.00.50.0Sum Energy for the Two Electrons (MeV)

Two Neutrino Spectrum Zero Neutrino Spectrum

1% resolution(2) = 100 * (0)

Q Endpoint

Energy

76Ge example

J.Thomas, UCL

Introduction:the experimentsTwo classes of approach to the experiment:

Detector IS the isotopeIonisation detectorsBolometer detectorsTPCs

Detector Contains the isotope(s)Tracking detectors

Measure half life, infer m Half life sensitivity given by experimental detailsG-phase space, exactly calculable:G0 ~ Q

5

M0-Nuclear Matrix Element, hard to calculateUncertain to factor 2-10, isotope dependentMotivation to measure several isotopes

J.Thomas, UCL

Introduction:the isotopes

What are the usable bb decay isotopes?76Ge, Q2.038MeV : MG = 7.3 +0.6 -0.6 x 10 -14

48Ca,Q 4.272MeV :MG = 5.4+3.0-1.4 x 10 -14

82Se, Q 2.995MeV : MG = 1.7+0.4-0.3 x 10 -13

100Mo, Q 3.034MeV :MG = 1.0+0.3-0.3 x 10 -12

116Cd,Q 2.804MeV :MG = 1.3+0.7-0.3 x 10 -13

130Te,Q 2.528MeV :MG = 4.2+0.5-0.5 x 10 -13

136Xe,Q 2.481MeV :MG = 2.8+0.4-0.4 x 10 -14

150Nd,Q 3.368MeV: MG = 5.7+1.0-0.7 x 10 -12

These can all be enriched by standard processes

J.Thomas, UCL

A History Plot

mscale 0.01 – 0.05 eV from oscillation experiments

TeO2

J.Thomas, UCL

Where are we today?People have been searching for double beta decay for many years : first suggested in 1937Presently three experiments taking data

CUORICINO : BolometerNEMO-III: TrackingHEIDLEBERG-MOSCOW : Ionization Ge detector

New improved Heidelberg-Moscow result shows 4.2 effect!Cuoricino and NEMO-III will reach this sensitivity

J.Thomas, UCL

Located in LNGS, Hall A

Cuoricino (Hall A)

CUORE R&D (Hall C)

CUORE (Hall A)

Today:CUORICINO

J.Thomas, UCL

Incident particle

absorber crystal

heat bath

Thermal sensor

Today: CUORICINO

2 modules, 9 detector each,crystal dimension 3x3x6 cm3

crystal mass 330 g

9 x 2 x 0.33 = 5.94 kg of TeO2

11 modules, 4 detector each,crystal dimension 5x5x5 cm3

crystal mass 790 g4 x 11 x 0.79 = 34.76 kg of

TeO2

40.7kg total

34% natural abundance

J.Thomas, UCL

Today:CUORICINO

J.Thomas, UCL

Today:CUORICINO130Te crysals in LNGSQ 2.528MeVOperation started early 2003Background 0.19 counts/kev/kg/yEnergy resolution 4eV at 2MeV127.5x1023 years

<m>=0.3-1.6eV : indicates large range of NME calculations available!

J.Thomas, UCL

Today: NEMO-III

AUGUST 2001

Located in Frejus Underground Lab

J.Thomas, UCL

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 (All the enriched isotopes produced in Russia)

Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

J.Thomas, UCL

events selection in NEMO-3

Deposited energy: E1+E2= 2088 keVInternal hypothesis: (t)mes –(t)theo = 0.22 nsCommon vertex: (vertex) = 2.1 mm

Vertexemission

(vertex)// = 5.7 mm

Vertexemission

Run Number: 2040Event Number: 9732Date: 2003-03-20

Typical 2 event observed from 100Mo

J.Thomas, UCL

(Data 14 Feb. 2003 – 22 Mar. 2004)

T1/2 = 7.72 0.02 (stat) 0.54 (syst) 1018 y

100Mo 22 preliminary results

4.57 kg.y

Cos()

Angular Distribution

Background subtracted

22 Monte Carlo

• Data

145 245 events6914 g

241.5 daysS/B = 45.8

NEMO-3

100Mo

E1 + E2 (keV)

Sum Energy Spectrum

145 245 events6914 g

241.5 daysS/B = 45.8

NEMO-3

100Mo

• Data

Background subtracted

22 Monte Carlo

Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

J.Thomas, UCL

Simkovic, J. Phys. G, 27, 2233, 2001

Single electron spectrum different between SSD and HSD

100Mo 22 Single Energy Distribution

22 HSDMonte Carlo HSD

higher levels Background subtracted

• Data22 SSD Monte Carlo

Background subtracted

• Data

SSDSingle State

HSD: T1/2 = 8.61 0.02 (stat) 0.60 (syst) 1018 y

SSD: T1/2 = 7.72 0.02 (stat) 0.54 (syst) 1018 y

100Mo 22 single energy distribution in favour of Single State Dominant (SSD) decay

4.57 kg.yE1 + E2 > 2 MeV

4.57 kg.yE1 + E2 > 2 MeV

HSD, higher levels contribute to the decay

SSD, 1 level dominates in the decay (Abad et al., 1984, Ann. Fis. A 80, 9)

100Mo

0

100Tc

1

/ndf = 139. / 36 /ndf = 40.7 / 36

NEMO-3 NEMO-3

Esingle (keV) Esingle (keV)

Esingle (keV)

Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

J.Thomas, UCL

Today:NEMO-IIIPresent 90%CL limits from NEMO-III(216.4 days)

82Se:T1/2() > 1.9 1023 y, m < 1.3 – 3.6 eVSimkovic et al., Phys. Rev. C60 (1999)Stoica, Klapdor, Nucl. Phys. A694 (2001)Caurier et al., Phys. Rev. Lett. 77 1954 (1996)

100Mo T1/2() > 3.5 1023 y, m < 0.7 – 1.2 eVSimkovic et al., Phys. Rev. C60 (1999)Stoica, Klapdor, Nucl. Phys. A694 (2001)

Expected Reach in 5 years after RadonPurification

100Mo T1/2() > 4.0 1024 y, m < 0.2 – 0.35 eV82Se:T1/2() > 8.0 1023 y,,m < 0.65 – 1.8 eV

J.Thomas, UCL

Today: Heidelberg-Moscow

Enriched Germanium ionisation detector

J.Thomas, UCL

Today: Heidelberg-Moscow

New analysis provides evidence of a peak at the expected valueTotal 71.7kgy of dataSignificance is 4.2 m 0.24-0.58eVCorresponds to quasi-degenerate neutrino masses

J.Thomas, UCL

Cosmological disfavoured Region (WMAP)

Direct hierarchym2

12=

m2sol

Inverse hierarchym2

12= m2atm

“quasi” degeneracym1 m2 m3

Present Cuoricino/NEMO-III region

Possible evidence (best value 0.39 eV)

Feruglio F. , Strumia A. , Vissani F. hep-ph/0201291

J.Thomas, UCL

Future PlansOnly a few approaches

Bolometers: Isotope is the detectorTracking : Isotope inside the detectorIonisation : Isotope is the detector

Simple formula relates experimental parameters to half life reach: background or no background:

a-isotopic abundance,b-background/Kev/kg/y,-efficiency,E-energy resolution,t-time,W-molecular weight,m-mass

J.Thomas, UCL

Future PlansThere are presently 16 projects in various stages of planning/approval in Italy,Japan,US,France and perhaps other places, target 0.02-0.05eV in mass

Highlight reach of a fewCUORE, 720kg TeO2, bolometersEXO, 1Tonne Xenon, TPC amd Ba identificationMAJORANA, 500kg Ge, ionizationSuper-NEMO several isotopes, tracking

Ionisation Cobra, CdTeGEM GENIUSMajoranaMPI

Scintillator CAMEO CdGANDLES CaCARVEL CdGSO GdXe Xe…….

Tracking, TPC, Drift

DCBA NdMOON MoSuper-NEMO Mo,Se,NdEXO Xe

J.Thomas, UCL

Future Plans : CUOREFirst fully-funded next generation experimentBased on CUORICINO technology, 130TeO2

Located at LNGSTarget background 0.001c/kev/kg720kg of TeO2

J.Thomas, UCL

Future Plans : EXOHigh Pressure Xe TPC with laser tagging of Ba daughter for background-free measurement2 Tonne of 136Xe at 10Atm or Liq Xe with cold-finger taggingEnergy resolution 2% at 2.5MeV200kg prototype of Liq Xe funded by DoE (no tagging) will be built at WIPP, New Mexico.200kg isotope already in hand

J.Thomas, UCL

Future Plans : Majorana/MPI

500kg enriched segmented conventional Ge detectorFeasability has been demonstrated, waiting for approvalWill use pulse-shape information to reduce backgroundBased on theory that dominant background is 68Ge from cosmogenics

MPI-Ge experiment also proposedUses Ge mono-crystal in Liquid N or Ar for passive/active shieldingBased on theory that dominant background is from Cu etc external to Ge

J.Thomas, UCL

Future Plans : Super-NEMO

Based on NEMO-III technology,SM only background study Se,Nd,Mo, low SM backgroundDesign study will start 2005Feasible if:

a) BG only from 2 (NEMO3)b)E/E = 10% at 1

MeV (8% has already been

demonstrated in recent R&D)

J.Thomas, UCL

Future PlansCertain factors dominate reach

Some factors are instrinsic to a particular isotope (M), others to the experimental approach

T01/2 given by experimental

parameters:background,resolution,efficiencyThe larger M, the lower the reach in m

J.Thomas, UCL

Future Plans : Summary

J.Thomas, UCL

ConclusionsVery exciting time for neutrino physics in general and 0 in particularA positive signal is now a serious possibility in light of oscillation resultsCosts of experiemnts all in the $50M range: this is small potatoes for the potential scientific gainIn light of large NME uncertainties, several isotopes should be measured to avoid disappointment