14-15. May 2005UK Forum Dark Matter, RAL Neutrino masses from double beta decay Kai Zuber University of Sussex.

14-15. May 2005 UK Forum Dark Matter, RAL

Neutrino masses from double beta decay

Kai ZuberUniversity of Sussex


Contents

• Introduction

• Double beta decay

• COBRA

• Outlook

• Summary and conclusions


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


Neutrinos in cosmology

Zur Anzeige wird der QuickTime™ Dekompressor „GIF“

benötigt.

M. Tegmark


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


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)


Neutrino mass schemes


Neutrinos mass density


Contents

• Introduction


• COBRA

• Outlook



• (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


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


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

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟


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


„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


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


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


0ν p

eak

regi

on

Spectrum


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)


„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


„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


Heidelberg-Moscow Evidence


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


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


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)


C0BRA

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 CdZnTe detectors

• Two isotopes at once

• 116Cd above 2.614 MeV


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


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


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


The solid state TPC

Single electron spectra

Angular correlationcoefficient

Introduce tracking properties by using segmented,Pixellated electrodes and pulse shape analysis


Pixellated detectors3D - Pixelisation:


Contents

• Introduction


• COBRA

• Outlook



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


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, ...


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


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


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


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:


++ - 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...


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 2005UK Forum Dark Matter, RAL Neutrino masses from double beta decay Kai Zuber University of Sussex.

Documents

uk forum dark matter

neutrino mass slide

ral cobra

ral isotopes

dortmund slide

tegmark slide

cdm slide

mev slide