14-15. May 2005 UK Forum Dark Matter, RAL
Neutrino masses from double beta decay
Kai ZuberUniversity of Sussex
14-15. May 2005 UK Forum Dark Matter, RAL
Contents
• Introduction
• Double beta decay
• COBRA
• Outlook
• Summary and conclusions
14-15. May 2005 UK Forum Dark Matter, RAL
Neutrino masses from cosmology
New WMAP measurement + SDSS data
Mass bound model dependent, currently done within CDM
€
Ων h2 =mν ,tot
94eV
€
nν =6ς (3)
11π 2TCMB
3 ≈112cm−3
14-15. May 2005 UK Forum Dark Matter, RAL
Neutrinos in cosmology
Zur Anzeige wird der QuickTime™ Dekompressor „GIF“
benötigt.
M. Tegmark
14-15. May 2005 UK Forum Dark Matter, RAL
Combined SDSS and WMAP dataM. Tegmark et al., Phys. Rev. D 69, 103501 (2003)
Neutrino mass from cosmology
Data Authors mν mi
2dFGRS Elgaroy et al. 02 < 1.8 eV
WMAP+2dF+… Spergel et al. 03 < 0.7 eV
WMAP+2dF Hannestad 03 < 1.0 eV
SDSS+WMAP Tegmark et al. 04 < 1.7 eV
WMAP+2dF+
SDSS
Crotty et al. 04 < 1.0 eV
Clusters +WMAP Allen et al. 04 0.56+0.30-0.26 eV
All upper limits 95% CL, but different assumed priors !All upper limits 95% CL, but different assumed priors !
O. Lahav, Neutrino 2004
14-15. May 2005 UK Forum Dark Matter, RAL
Oscillation evidences
LSND
Atmospheric
Solar + reactors
sin2 2 = 10-1-10-3 , m2 = 0.1-6 eV2
sin2 2 = 1.00 , m2 = 2.1 10-3 eV2
sin2 2 = 0.81 , m2 = 8.2 10-5 eV2
If all three are correct... we need more (sterile ones)
14-15. May 2005 UK Forum Dark Matter, RAL
Neutrino mass schemes
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Neutrinos mass density
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Contents
• Introduction
• Double beta decay
• COBRA
• Outlook
• Summary and conclusions
14-15. May 2005 UK Forum Dark Matter, RAL
• (A,Z) (A,Z+2) + 2 e- + 2νe 2ν • (A,Z) (A,Z+2) + 2 e- 0ν
-
0+1+
0+(A,Z)(A,Z+1)
(A,Z+2)
0ν: Only possible if neutrinos are Majorana particles
In nature there are 35 isotopes
Double beta decay
2ν: Seen in 10 isotopes, important for nuclear physics input
14-15. May 2005 UK Forum Dark Matter, RAL
Spectral shapes
Sum energy spectrum of both electrons
0ν: Peak at Q-value of nuclear transition
T1/2 a • (M•t/E•B)1/2
1 / T1/2 = PS * NME2 * (mν / me)2
Measured quantity: Half-life
Dependencies (BG limited)
link to neutrino mass
14-15. May 2005 UK Forum Dark Matter, RAL
3 Flavour oscillations (PMNS)
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
ννν
⇒⇒⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
ννν
⎥⎥⎥
⎦
⎤
⎢⎢⎢
⎣
⎡=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
ννν
τ
μν
τττ
μμμ
τ
μ
e2i
3
2
1
321
321
3e2e1ee
E2
m
UUU
UUU
UUU
Analogous to CKM matrix
solar If sin 13 0 CP-violation atmospheric
U= UPMNS diag(1,e i ,e i )Majorana:€
U =
cosθ12 sinθ12 0
−sinθ12 cosθ12 0
0 0 1
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
cosθ13 0 sinθ13e−iδ
0 1 0
−sinθ13eiδ 0 cosθ13
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
1 0 0
0 cosθ23 sinθ23
0 −sinθ23 cosθ23
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
1 0 0
0 e iβ 1 0
0 0 e iβ 2
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
14-15. May 2005 UK Forum Dark Matter, RAL
Physical quantities
Experimental observable: Half-life
Double beta decay: Effective Majorana neutrino mass
Beta decay
ki
kekk
kekee meUmUmm ek
ν ∑∑ ==≡22
me = |Uek|2 mk
relative CP phases = 1
14-15. May 2005 UK Forum Dark Matter, RAL
„inverted“ mass hierarchy m3 < m1 < m2
hierarchical
quasi-degenerate
Neutrino mass schemes and DBD „normal“ mass hierarchy m1<m2<m3
almost degenerate neutrinos m1≈ m2≈ m3
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Phase space ν ν decay rate scales with Q5
2νν decay rate scales with Q11
Q-value (keV)
Isotope Nat. abund. (%)
(PS 0v)–1 (yrs)
(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 2809 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
14-15. May 2005 UK Forum Dark Matter, RAL
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 7676GeGe • Lead box and nitrogen flushing ofLead box and nitrogen flushing of the detectors the detectors • Digital Pulse ShapeDigital Pulse Shape Analysis (factor 5 reductionAnalysis (factor 5 reduction)) Peak at 2039 keVPeak at 2039 keV
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0ν p
eak
regi
on
Spectrum
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Evidence for 0ν-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 and more
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)
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„Evidence“ I
Statistical significance: 53.93 kg x yr
Apply pulse shape 28 kg x yr
Ignore det. 4 (no muon veto, slightly worse energy resolution)
Completely new statistical treatment - Bayesian method
Only region of 5 around peak is used for background determination
Step 1
Step 2
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„Evidence“ II Step 1 Step 2
For the double beta line they restrict themselves to 5 SD region
Left hand side BG too high, hence for right hand side onlyregion without lines except the double beta one
Some lines known, some are not
14-15. May 2005 UK Forum Dark Matter, RAL
Heidelberg-Moscow Evidence
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Heidelberg -Moscow
Evidence ?
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
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If peak is real...
Is peak something specific to Ge?
Uncertainties in the nuclear matrix elements?
Check with a different isotope
Physics mechanism at work ? Tracking
1.) Go out and check (GERDA, MAJORANA)
2.) NEMO, COBRA
n
n
p
pe
e
14-15. May 2005 UK Forum Dark Matter, RAL
Running experiments
DBD Q-value
CUORICINO: cryogenic bolometers40.7 kg TeO2
Future: CUORE760 kg TeO2
approved
NEMO-3: TPC
10 kg enriched foils,6 kg 100Mo
Idea: Super-NEMO (100 kg)
T1/2 > 1.8 x 1024 yr (90% CL) Arnaboldi et al, hep-ex/050134
T1/2 > 3.1 x 1023 yr (90% CL)
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C0BRA
Use large amount of CdZnTe Semiconductor Detectors
Array of 1cm3
CdTe detectors
K. Zuber, Phys. Lett. B 519,1 (2001)
14-15. May 2005 UK Forum Dark Matter, RAL
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
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Advantages• Source = detector
• Semiconductor (Good energy resolution, clean)
• Room temperature (safety)
• Tracking („Solid state TPC“)
• Modular design (Coincidences)
• Industrial development of CdZnTe detectors
• Two isotopes at once
• 116Cd above 2.614 MeV
14-15. May 2005 UK Forum Dark Matter, RAL
Cobra - The people
T. Leigertwood, D. McKechan, C. Reeve, J. Wilson, K. Zuber
C. Gößling, H. Kiel, D. Münstermann, S. Oehl, T. VillettUniversity of Dortmund
University of Sussex
Laboratori Nazionali del Gran SassoM. Junker
University of WarwickP.F. Harrison, B. Morgan, Y. Ramachers, D. Stewart
T. Bloxham, M. Freer
P. Seller
B. Fulton, R. Wadsworth
A. Boston, P. Booth, P. Nolan
University of Birmingham
University of Liverpool
University of York
Rutherford Appleton Laboratory
14-15. May 2005 UK Forum Dark Matter, RAL
The 2x2 prototype
4 naked 1cm3 CdZnTe
Very preliminary
2.5 kg x days of data
0ν r
egio
n T
e130
0ν r
egio
n C
d116
Installation of setup at Gran Sasso Underground Laboratory
Cd113
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The 64 detector arrayAim for next 2 years: The next step towards a large scale experiment,Scalable modular design, explore coincidences
Include:CoolingNitrogen flushing
Mass factor 16 higher,about 0.4 kg CdZnTe
Physics: - Can access2νECEC in theoreticallypredicted region-Precision measurement of 113Cd- New limitsPart of the detectors at Dortmund
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The solid state TPC
Single electron spectra
Angular correlationcoefficient
Introduce tracking properties by using segmented,Pixellated electrodes and pulse shape analysis
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Pixellated detectors3D - Pixelisation:
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Contents
• Introduction
• Double beta decay
• COBRA
• Outlook
• Summary and conclusions
14-15. May 2005 UK Forum Dark Matter, RAL
0ν ν Experimental Situation
Experiment Isotope T1/20ν (y) <mν> (eV)
You Ke et al. 1998 48Ca > 9.5 1021 (76%) < 8.3Klapdor-Kleingrothaus 2001 76Ge > 1.9 1025 < 0.35Aalseth et al 2002 > 1.57 1025 < 0.33 - 1.35Arnold et al. 2004 82Se > 1.3 x 1023 < 1.5-3.1Arnold et al. 2004 100Mo >3.1 1023 < 0.33-0.84Danevich et al. 2000 116Cd > 1 1023 < 2.2Bernatowicz et al. 1993 130/128Te* (3.52 0.11) 10-4 < 1.1 – 1.5Bernatowicz et al. 1993 128Te* > 7.7 1024 < 1.1 – 1.5Arnaboldi et al. 2005 130Te > 1.8 1024 < 0.5 – 1.1Luescher et al. 1998 136Xe > 4.4 1023 < 1.8 – 5.2Belli et al. 2001 136Xe > 7 1023 < 1.4 – 4.1De Silva et al. 1997 150Nd > 1.2 1021 < 3Danevich et al. 2001 160Gd > 1.3 1021 < 26
2 main experimental approaches2 main experimental approaches::
• Active SourceActive Source• Passive SourcePassive Source
Best 0Best 0νν22 results involve active source experiments results involve active source experiments
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Back of the envelope
1/2 = ln2 • a • NA• M • t / N (τT) ( 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, ...
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2ν - decay
+ Tracking option
€
F =8Q(ΔE /Q)6
me
= 3.7*10−10
S. Elliott, P. Vogel, Ann. Rev. Nucl. Part. Sci. 2002
Energy resolution important semiconductor
Fraction of 2ν in 0 ν peak:
Signal/Background:
4331
02/1
22/1 == ν
ν
TT
FBS
yrsT 1922/1 102.3 ×=ν
yrsT 2602/1 102×=ν
2ν is ultimate, irreducible background
14-15. May 2005 UK Forum Dark Matter, RAL
Future projectsExperiment Author Isotope Detector description T5y
1/2(y) <mν>*
COBRA Zuber 2001 116Cd 10 kg CdTe semiconductors 1 x 1024 0.71
CUORICINOArnaboldi et al 2001
130Te 40 kg of TeO2 bolometers 1.5 x 1025 0.19
NEMO3 Sarazin et al 2000 100Mo 10 kg of bb(0n) isotopes (7 kg Mo) with tracking 4 x 1024 0.56
CUOREArnaboldi et al. 2001
130Te 760 kg of TeO2 bolometers 7 x 1026 0.027
EXODanevich et al 2000
136Xe 1 t enriched Xe TPC 8 x 1026 0.052
GEMZdesenko et al 2001
76Ge 1 t enriched Ge diodes in liquid nitrogen + water shield 7 x 1027 0.018
GENIUSKlapdor-Kleingrothaus et al 2001
76Ge 1 t enriched Ge diodes in liquid nitrogen 1 x 1028 0.015
MAJORANA Aalseth et al 2002 76Ge 0.5 t enriched Ge segmented diodes 4 x 1027 0.025DCBA Ishihara et al 2000 150Nd 20 kg enriched Nd layers with tracking 2 x 1025 0.035CAMEO Bellini et al 2001 116Cd 1 t CdWO4 crystals in liquid scintillator > 1026 0.069CANDLES Kishimoto et al 48Ca several tons of CaF2 crystal in liquid scintillator 1 x 1026
GSO Danevich 2001 160Gd2 t Gd2SiO5:Ce cristal scintillator in liquid scintillator
2 x 1026 0.065
MOON Ejiri et al 2000 100Mo 34 t natural Mo sheets between plastic scintillator 1 x 1027 0.036
XeCaccianiga et al 2001
136Xe 1.56 t of enriched Xe in liquid scintillator 5 x 1026 0.066
XMASSMoriyama et al 2001
136Xe 10 t of liquid Xe 3 x 1026 0.086
* Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31
O.Cremonesi, ν 2002
14-15. May 2005 UK Forum Dark Matter, RAL
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)
MERGE
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EXO
Tracking and scintillation136136Xe 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:
14-15. May 2005 UK Forum Dark Matter, RAL
++ - modes
• (A,Z) (A,Z-2) + 2 e+ (+2νe) ++ • e- + (A,Z) (A,Z-2) + e+ (+2νe ) +/EC
• 2 e- + (A,Z) (A,Z-2) (+2νe) EC/EC
Important to reveal mechanism if 0ν is discoveredEnhanced sensitivity to right handed weak currents
(V+A)
n
n
p
pe
eIn general:
Q-4mec2
Q-2mec2
Q
Double charged higgs bosons,R-parity violating SUSY couplings,leptoquarks...
14-15. May 2005 UK Forum Dark Matter, RAL
Summary
A lot of proposals and R&D projects among them is COBRA using CdZnTe semiconductors
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
14-15. May 2005 UK Forum Dark Matter, RAL