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