Search for Majorana neutrinos

and double beta decay experiments

Xavier Sarazin

Laboratoire de l’Accélérateur Linéaire

(CNRS-IN2P3, Univ. Paris-Sud 11)

Only two n states:

|nL, h= -1/2 > CPT |nR, h= +1/2 >

Neutrino is the only fermion with Q = 0

Neutrino might be a Majorana particle n = n ?

Massive Majorana n Violation of the Leptonic Number

Leptogenesis in the Early Universe through the Majorana neutrino

See-saw mechanism to explain the small mass of the neutrino

Observation of bb0n decay is the most sensitive way to probe Majorana

Majorana Neutrino

For few isotopes, b-decay is forbiden bb2n process (second order b-decay)

bb2n and bb0n decay

Energy Sum of the two electrons Qbb

For few isotopes, b-decay is forbiden bb2n process (second order b-decay)

bb2n and bb0n decay

Energy Sum of the two electrons

If neutrino is a Majorana particle bb0n Process

bb0n

Process L = 2

• Majorana neutrino exchange

mn

• Right Handed weak current

V+A

• Majoron production

• Exchange of SUSY particles

Qbb

Energy and angular distributions

will be different !

2200

102/1 eemMT nnn =

-

Theoretical predictions

Phase space

factor

Nuclear Matrix Element

Theoretical uncertainty

Effective mass

Constraint

by n oscillations

=

i

eiee imUm n

2

In the case of an standard exchange of a Majorana neutrino

Merle & Rodejohann PRD 73, 073012 (2006)

Constraints from neutrino oscillations

In the case of an standard exchange of a Majorana neutrino

Degenerate masses

meV 502321 > atmmmmmm n

meV 50mν >

Normal hierarchy

?mν

Inverted hierarchy

meV 50m10 ν

Nuclear Matrix Elements

Calculated T1/2(bb0n) to start exploring the Inverted Hierarchy

in the case of exchange of Majorana neutrino

mn 50 meV

from Duek et al. , Phys. Rev. D 83 (2011)

• QRPA Tüe. Simkovic, Phys. Rev. C 79

(2009); Fang, Phys. Rev. C 82 (2010)

• QRPA Jy. Kortelainen, Phys. Rev. C 75

and C 76 (2007)

• NSM Shell Model Menendez, Nucl.

Phys. A818 (2009); Phys. Rev. C 80 (2009)

• IBM Interacting Boson Model Barea, Phys. Rev. C79 (2009)

• GCM Generating Coordinate Method Rodriguez, Phys. Rev. Lett. 105 (2010)

• PHFB Projected Hartree-Fock-

Bogoliubov Rath, Phys. Rev. C 82 (2010)

~ 3 1025

~ 3 1027

Nnuclei (76Ge)

≈ 10×Nnuclei (100Mo, 150Nd)

obs

excl

avogT

bkgN

M

A

NT

2ln02/1

nbb >

Sensitivity

M Large Mass of enriched bb isotopes

High efficiency

Nexcl Low background

High energy resolution

Cosmic rays and induced g’s underground lab

High energy g’s up to ~ 10 MeV produced by neutron captures

Natural radioactivity (238U and 232Th chain):

208Tl, 214Bi, Radon (222Rn) and Thoron (220Rn), a-decay (in case of no e-/a discrimination)

208Tl: Qb= 2.4 MeV + g 2.6 MeV

214Bi: Qb = 3.2 MeV

Ultra low radioactive detectors:

Detector materials: A(208Tl) < 1 mBq/kg

Source A(208Tl) < 1-10 mBq/kg

For comparison, a standard Al foil: A(208Tl) ~ 100 mBq/kg

Origin of background

Current best limits obtained in bb0n search

mn limit

(eV)

Limits at 90% C.L.

Inverted hierarchy

GERDA NEMO-3 Cuoricino

Kamland-Zen

EXO-200

T1/2(0n) limit

(1024 yrs) 1024 yrs

1 ev

Calorimeters

Ge diodes

Ionisation

Bolometers

Phonon + Scint.

Scintillators

Scintillations

Liq. Xe TPC

Ionisation+scint.

Gerda (76Ge)

Majorana (76Ge)

Cuore (130Te)

Lumineu (100Mo)

Lucifer (82Se)

Amore (100Mo)

Kamland-Zen (136Xe)

SNO+ (130Te)

Candles-3 (48Ca)

EXO (136Xe)

Tracko-Calo SuperNEMO

(76Se, 150Nd, 48Ca)

Gas Xe TPC

Ionisation

NEXT

(136Xe)

Pixel. CdZnTe

Ionisation

Cobra

(116Cd)

Electron Tracking

Ge diodes

GERDA (LNGS) 76Ge (Qbb = 2040 keV)

“Bare” Ge crystals in Liquid Argon

- Liq. Argon = cryostat + shield

- Ext. Water tank for shield + m-veto

- Detector arrays gradual deployment

GERDA (LNGS)

“Bare” Ge crystals in Liquid Argon

- Liq. Argon = cryostat + shield

- Ext. Water tank for shield + m-veto

- Detector arrays gradual deployment

76Ge (Qbb = 2040 keV)

Phase 1 (2011-2013) ~ 18 kg 76Ge

8 old 76Ge detectors (HdM, IGEX)

5 new BEGe detectors

FWHM ~ 3 keV @ 2.6 MeV for BEGe

Energy peaks stable within 1 keV

21.6 kg.yr 76Ge exposure

Bkg ~ 10-2 cts/keV/kg/yr

This is 10 times lower than previous Ge experiments !

T1/2(bb0n) > 2.1 1025 yr (90% C.L.)

Without PSA

With PSA

Mod. Phys. Lett. A 29, 1430001 (2014)

GERDA (LNGS)

“Bare” Ge crystals in Liquid Argon

- Liq. Argon = cryostat + shield

- Ext. Water tank for shield + m-veto

- Detector arrays gradual deployment

76Ge (Qbb = 2040 keV)

Phase 2 (2014) ~ 50 kg 76Ge

30 new Broad Energy (BEGe) detectors

High pulse shape discrimination performances

Single Site (bb0n) / Multi Sites (g bkg) discrimination

Detection of Ar scintillation light

Liquid Argon as active shield with the scintillation veto

Target : Bkg ~ 10-3 cts/keV/kg/yr

T1/2(bb0n) > 2 1026 yr in 5 yrs of data

MAJORANA 76Ge (Qbb = 2040 keV)

Under construction in Sanford Underground Laboratory (USA)

Up to 40 kg of HBGe crystals

Standard shield with electroformed Copper and lead

Start data with first cryostat end 2014

LOI between GERDA & MAJORANA Collaborations

Intention to merge for O(1 ton) exp. selecting the best technologies

Bolometers

T1/2(bb0n) > 2.8 1024 y (90%C.L.)

CUORICINO (2003 – 2008)

40 kg natTe02 ~ 10 kg 130Te

BKG = 0.17 cts/(keV.kg.yr)

~ 70% a’s from crystals and Cu surfaces

~ 30% external 2.6 MeV g-ray (208Tl) from cryostat

Qbb(130Te) ~ 2530 keV

~50 crystals natTeO2

FWHM ~ 6 keV @ Qbb

60Co

natTe02 crystal CUORICINO (LNGS, Italy)

Astropart. Phys. 34, 822 (2011)

CUORE (start 2015)

19 Cuoricino-like towers in a new cryostat

740 kg natTe02 200 kg 130Te

Sensitivity expected in 5 years

T1/2(bb0n) > 1026 y

Target: Bkg = 0.01 cts/(keV.kg.yr)

(17 times lower than Cuoricino)

CUORE-0 = 1st CUORE tower running in the cuoricino cryostat

Preliminary result of the background measurement

• a bkg reduced by a factor 6

• g bkg still dominated by cuoricino cryostat: we must wait for the new cuore cryostat

natTe02 crystal CUORE (LNGS, Italy)

Expected CUORE bkg = 0.01 cts/(keV.kg.yr)

~ 35 cts/year in the bb0n energy window (fwhm)

This is still a high level of bkg !

CUORE bkg must be reduced by an extra factor 10 at least !

The way to reach a « zero bkg » with bolometers:

Rejection 2.6 MeV g-ray bkg use crystal with Qbb > 2.6 MeV

• ZnMoO4, CaMoO4 (100Mo, Qbb= 3 MeV)

• ZnSe (82Se, Qbb= 3 MeV)

• CdWO4 (116Cd, Qbb= 2.8 MeV)

Rejection a bkg Scintillating bolometers for a / (e-,g) discrimination

S. Pirro et al. Physics of Atomic Nuclei, 69 (2006)

Scintillating bolometers

Scintillation signal

a/(e-,g) discrimination

Heat signal

Energy measurement

Ge plate Lumineu R&D

ZnMoO4 (313g)

141 h @ LSM

Expected bkg using CUORICINO contaminations

bkg = 10-3 – 10-4 cts/(keV.kg.y)

T1/2 ~ 1026 yrs with only 1 cuoricino-like tower !

(instead of 19…)

3 experiments are starting:

LUMINEU: Zn100MoO4 crystal (France)

LUCIFER: Zn82Se crystal (Italy)

AMORE: 40Ca100MoO4 crystal (Korea)

Scintillating bolometers

136Xe TPC

Experiments Several advantages to study Xenon

Simplest and least costly bb isotope to enrich

High bb2n half-life T1/2(136Xe) ~ T1/2(

76Ge) ~ 2 1021 yrs

Natural candidate for TPC

- Liq. TPC: EXO-200

- Gas TPC: NEXT

Limitation:

2447 keV g-ray from 214Bi, very close to Qbb = 2462 keV

The energy resolution must be better than ~15 keV (0.6%) at Qbb

Liq. Xe TPC (200 kg Xe, 80% enrich. 136Xe)

Fiducial Volume 76.5 kg 136Xe

Anti-correlation ionisation/scintillation

E = 3.6 % FWHM @ Qbb (E ~ 90 keV)

477.6 days (Sept. 2011 – Sept. 2013), 100 kg.yr

EXO-200 (WIPP, USA)

Bkg = (1.7 0.2 10-3 cts/(keV.kg.yr) 28 cts/(fwhm.yr)

Radon (214Bi) dominant bkg 2447 keV g-ray from 214Bi, very close to Qbb = 2462 keV

T1/2(bb0n) > 1.1 1025 yrs

(90% C.L.)

Nature 510, 229 (2014)

Next step: Radon suppression

Future project: nEXO with 5 tons 136Xe

Gas Xe TPC

~ 100 – 150 kg Xe gas,

>90% enrich. 130Xe

Electroluminescence technique for

the TPC readout

NEXT (CANFRANC, SPAIN)

Better Energy resolution

Target: E = 1 % FWHM @ Qbb (E ~ 25 keV)

Results of the NEXT-DEMO (a worst geometry):

1.7% FWHM at 511 keV (extrapolating to 0.77% FWHM at 2.5 MeV) has been obtained

Electron tracking by topological detection of the characteristic blob at the end of the track

NEXT-DEMO: electrons are identified in 98.5% of the cases

JINST 8 P04002 (2013) (arXiv:1211.4838)

TDR, JINST 7 (2012) T06001

Large

Liquid Scintillators

Reuse the available large liquid scintillator n experiments by loading 136Xe or natTe

KamLAND KamLAND-Zen with 136Xe

SNO SNO+ with natTe

Advantage: one can measure a large mass of bb isotope

Limitation: the background is relatively high and the energy resolution is modest

Kamland-Zen

• 320 kg of 136Xe loaded in 13 tons Liq. Scint.

Xe concentration ~ 2.45 %

(~700 kg 136Xe available in Kamioka mine)

• Energy resolution fwhm = 10 % (~240 keV) at Qbb

• Fiducial volume ~ 43 %

110Ag contamination

from Fukushima fallouts

KamLAND-Zen Phase I

Kamland-Zen

KamLAND-Zen Phase II: 114.8 days (Dec. 2013 – May 2014)

Next steps

KamLAND-Zen Next Phase (funded):

New inner balloon with 800 kg of load 130Xe T1/2(bb0n) > 1026 yrs

KamLAND2-Zen

High energy resolution with pressurized Xenon

R<1m

Phase I: T1/2(0n) > 1.9 1025 y

Phase II: T1/2(0n) > 1.3 1025 y

Phases I+II: T1/2(0n) > 2.6 1025 y (90% C.L.)

383 kg 136Xe

LS purification

Xe purification

Film surface cleaning by LS flow

110Ag reduction factor > 10

bkg ~ 10 cts / (fwhm.yr)

SNO+

SNO detector filled with liquid scint. and load 130Te

First data foreseen

end of 2014

• 130Te large nat. abundance (34%) : 0.3% natTe in 1 kt LS ~ 800 kg 130Te

Fiducial volume ~20% 160 kg 130Te

• High light yield of loaded Te liquid scintillator: Energy resolution E ~ 8 % at Qbb

• High T1/2(bb2n) : bb2n bkg reduced

• LS must be ultra radiopure in 238U and 232Th (~BOREXINO)

• Solar 8B n is the ultimate bkg !

2 years of data

T(bb0n) = 6 1024 y

NEMO

Tracko-Calo

Direct reconstruction of the two electrons

Can distinguish a possible bb0n signal to a unknown g line

Direct measurement of the various components of background

Bkg measured separately with dedicated event topology (e-, e+, g, a)

NEMO combines a tracking detector and a calorimeter

NEMO, a tracko-calo approach

Running from Feb. 2003 until Jan. 2011 in Modane Underground Laboratory (4800 m.w.e.)

NEMO-3 (LSM Modane)

Source: ~ 20 m2 of bb sources foils (~50 mg/cm2)

bb0n: 7 kg of 100Mo, 1 kg of 82Se

bb2n: 0.4 kg 116Cd, 37 g 150Nd, 9 g 96Zr, 7 g 48Ca …

Tracking detector: drift cells in Geiger mode

Calorimeter: ~ 2000 plastic scint. + 5” PMTs

E/E ~ 15% (FWHM) @ 1 MeV

Display of a bb0n candidate

34.3 kg.yr 100Mo, T1/2(0n) > 1.1 1024 yrs (90% C.L.)

NEMO-3 (LSM Modane)

700.000 bb

events

ETOT(MeV)

cos

NEMO-3 bkg ≈ 0.4 cts/(kg.yr)

Source: ~ 5×3 m2 foil (40 mg/cm2): 82Se, 150Nd, 48Ca

Tracking: Drift cells in Geiger mode

Calorimeter: plastic scintillators + 8" PMT’s

20 modules to be installed in the future extension of LSM

NEMO-3 extrapolation

100 kg of 82Se to reach T1/2(bb0n) ≥ 1026 years

Bkg must be reduced by a factor ~ 40

SuperNEMO (LSM Modane)

First module (demonstrator) in construction

Start data end 2015 in Modane

Target: bkg < 10-2 cts/(kg.yr) in the bb0n ROI

NEMO-3 bkg = 0.4 cts/(kg.yr)

CONCLUSIONS

2010 – 2020: New generation of bb experiments with few 100 kg of isotope

Experiments using 136Xe provided already first results with ~100 kg !

• Kamland-Zen (using available large liquid scint. detector)

• EXO-200 Liq. TPC

New experiments started

• GERDA Phase 1: results in Summer 2013

Target bkg Phase-1 has been reached : bkg ~ 0.01 cts/(keV.kg.y)

GERDA Phase 2 is starting: Target bkg ~ 0.001 cts/(keV.kg.yr) with 50 kg 82Ge

• CUORE-0 : preliminary results bkg is at least 2 times too high

New experiments in construction

• LUCIFER & LUMINEU: scintillating bolometer to reach bkg 0.001cts/(keV.kg.yr)

Can measure Se and Mo

• SNO+ with natural Te: can start measuring ~ 160 kg of 130Te in 2015

And even larger mass (up to 8 tons ?) if the bkg is low enough

• SuperNEMO with the direct detection of the two emitted e-

• NEXT-100 (gaseous Xe TPC)

7

100

100

90

160

800 (0.3%)

8000 (3%)

380

800

19

12

230

200

30

20

50

200

Mass

(kg)

201545 – 9513550.9130TeCUORE

R&D

50 – 120

35 – 95

10 – 25

1.

0.7

10

0.15

0.15

2.7

50.9

82Se100Mo100Mo

ZnSe (1 tower)

ZnMoO4 (1 tower)

ZnMoO4 (19 towers)

Published

2015

120 – 280

35 – 85

0.26

1102400.4136Xe

Kamland-Zen

Next-Phase

2014

2016……Few tens2000.2130TeSNO+

Published

2015

190 – 450

75 – 185

0.1

0.6

28

?900.5130Xe

EXO-200

Rn removed

201460 – 15010.1530.976GeMajorana

SuperNEMO

NEXT-100

GERDA-I

GERDA-II

GERDA-III

Experiment

82Se82Se

150Nd

130Xe

76Ge

Isotope

0.2

0.3

0.9

0n

2015

?

?

190 – 460

50 – 120

30 – 115

0.07

1

1

0.07

1

1

200

201560 – 14510.525

Published

2014

?

200 – 500

40 – 105

30 – 75

0.2

2.

10.

1.5

0.15

0.6

3.5

Start

Data

mn

limit

(eV)

T1/2(0n)

limit

(1026 yrs)

bkg@Qbb

cts/(fwhm.y)

E@Qbb

(fwhm)

(keV)

7

100

100

90

160

800 (0.3%)

8000 (3%)

380

800

19

12

230

200

30

20

50

200

Mass

(kg)

201545 – 9513550.9130TeCUORE

R&D

50 – 120

35 – 95

10 – 25

1.

0.7

10

0.15

0.15

2.7

50.9

82Se100Mo100Mo

ZnSe (1 tower)

ZnMoO4 (1 tower)

ZnMoO4 (19 towers)

Published

2015

120 – 280

35 – 85

0.26

1102400.4136Xe

Kamland-Zen

Next-Phase

2014

2016……Few tens2000.2130TeSNO+

Published

2015

190 – 450

75 – 185

0.1

0.6

28

?900.5130Xe

EXO-200

Rn removed

201460 – 15010.1530.976GeMajorana

SuperNEMO

NEXT-100

GERDA-I

GERDA-II

GERDA-III

Experiment

82Se82Se

150Nd

130Xe

76Ge

Isotope

0.2

0.3

0.9

0n

2015

?

?

190 – 460

50 – 120

30 – 115

0.07

1

1

0.07

1

1

200

201560 – 14510.525

Published

2014

?

200 – 500

40 – 105

30 – 75

0.2

2.

10.

1.5

0.15

0.6

3.5

Start

Data

mn

limit

(eV)

T1/2(0n)

limit

(1026 yrs)

bkg@Qbb

cts/(fwhm.y)

E@Qbb

(fwhm)

(keV)

SUMMARY

N.M.E. from Duek et al. , Phys. Rev. D 83 (2011) In italic: performances already achieved Otherwise, numbers must be demonstrated

EXTRA SLIDES

Isotope Experiment Technique Mass of

isotope bb0n

Bkg cts /(kg.y.fwhm)

T1/2 (0n) Limit (90%)

mn (eV)

Min. Max.

48Ca CANDLES Scintillation 0.01 kg ~ 1 - > 5.8 1022 3.55 9.91

76Ge GERDA Ionisation 20 kg ~ 1 0.05 > 2.1 1025 0.2 0.5

82Se NEMO-3 Tracko-calo 1 kg ~ 0.1 0.3 > 3.2 1023 0.85 2.08

100Mo NEMO-3 Tracko-calo 7 kg ~ 0.1 0.5 > 1.0 1024 0.31 0.79

116Cd Solotvina Scintillation 80 g ~ 1 - > 1.7 1023 1.22 2.30

130Te CUORICINO Bolometer 10 kg ~ 1 1.1 > 2.8 1024 0.27 0.57

136Xe EXO-200 TPC Xe liq 160 kg ~ 0.4 0.025 > 1.1 1025 0.19 0.45

136Xe Kamland-Zen Liq. Scint. 130 kg ~ 0.5 110mAg > 2.6 1025 0.13 0.31

150Nd NEMO-3 Tracko-calo 0.04 kg ~ 0.1 0.5 >1.8 1022 2.35 8.65

Current best limits obtained in bb0n search

Natural radioactive chains

Low Qbb

Low 0n

34% nat.

abundance

Large available mass

Low Qbb

Bi g ray at

Experiment Isotop

e

Mass

(kg) 0n

E@Qbb

(fwhm)

(keV)

bkg@Qbb

cts/(fwhm.

y)

T1/2(0n)

limit

(1026

yrs)

mn

limit

(eV)

Start

Data

GERDA-I

GERDA-II

GERDA-III

76Ge

20

50

200

0.9 3.5

1.5

0.15

0.6

0.2

2.

10.

200 – 500

40 – 105

30 – 75

Publishe

d

2014

?

Majorana 76Ge 30 0.9 3 0.15 1 60 – 150 2014

CUORE 130Te 200 0.9 5 35 1 45 – 95 2015

ZnSe (1 tower)

ZnMoO4 (1 tower)

ZnMoO4 (19

towers)

82Se

100Mo 100Mo

19

12

230

0.9 5

0.15

0.15

2.7

1.

0.7

10

50 – 120

35 – 95

10 – 25

R&D

Kamland-Zen

Next-Phase 136Xe

380

800 0.4 240 10

0.26

1

120 – 280

35 – 85

Publishe

d

2015

SNO+ 130Te 800 (0.3%)

8000 (3%) 0.2 200 Few tens … …

2014

2016

EXO-200

Rn removed 130Xe 160 0.5 90

28

?

0.1

0.6

190 – 450

75 – 185

Publishe

d

2015

NEXT-100 130Xe 90 0.3 25 0.5 1 60 – 145 2015

SuperNEMO

82Se 82Se

150Nd

7

100

100

0.2 200

0.07

1

1

0.07

1

1

190 – 460

50 – 120

30 – 115

2015

?

?

N.M.E. from Duek et al. , Phys. Rev. D 83 (2011)

SUMMARY

In italic: performances already achieved Otherwise, numbers must be demonstrated