status of experimental searches for neutrinoless double beta decay

8/13/2019 Status of experimental searches for Neutrinoless double beta decay

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Beta Decays

Transitions in nucleus

proton neutrons

neutron proton

)(

)(

)(

,1,

,1,

,1,

nepMMe

peneMM

nepeMM

eAZAZ

eAZAZ

eAZAZ

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http://ik1au1.fzk.de/~katrin/index.html


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Beta Decay -Quark level Feynman Diagrams

The proton is made of 3 quarksuud (up, up, down)

The neutron is made also of 3 quarks - udd

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The neutrino is needed to conserve angular momentum

(Z,A) (Z+1,A)

for A=even have either

Z,N even-even odd-odd or

Z,N odd-odd even-even p, n both spin 1/2 and so for even-even or odd-odd

nuclei I=0,1,2,3.

But electron has spin 1/2

I(integer) I(integer) + 1/2(electron) doesntconserve J

need spin 1/2 neutrino

Beta Decaywhy neutrino?

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Also observed that electron spectrum is continuous indicative of

>2 body decay

Beta Decaywhy neutrino?

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Signature: Sharp peak at Q-value of the decay

2 neutrinos

escape the

detector

undetected:continuous

spectrum

Total energy of

decay is

deposited

within

detector:sharp peak

Effective Majorana neutrino mass:

= ||Uei|2eiimi|

Neutrinoless double beta decay

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Probe of neutrino nature.Neutrinos are Majorana fermions (particle antiparticle) if 0 takes place Leptogenesis, Baryon asymmetry, CPviolation

Neutrino mass hierarchy.0 measurements might help toestablish the right one.

Absolute mass scale.0 experiments are among the mostsensitive ones.

Spreads are

due to

variations of

unknown

CP phases

0 and neutrino fundamental properties

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How experimental parameters are connected to the Majorana mass

sensitivity of experiment?

sensitivity F: lifetime corresponding to the minimum detectable numberof events over background at a given confidence level

background level

F (MT / bDE)1/2

energy resolution

live time

source mass

F MT

importance of the nuclide choice

sensitivity to m (F/Q |Mnucl|2)1/2 1 bDEMTQ1/2

1/4

|Mnucl|

b 0 b = 0b: specific background coefficient

[counts/(keV kg y)]

Experimental parameters

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Natural radioactivity of materials

(source itself, surrounding structures)

Neutrons

Cosmogenic induced activity (long living)

2 Double Beta Decay

Background Sources

Levels of < 1 mBq / kg are required for some materials at the ton scale

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e-

e-

Source Detector

Easy to approach the ton scale

e-

e-source

detector

detector

Source Detector

Easy to get tracking capability

High energy resolution (2%)

Tracking / topology capabilityEasy to approach zero backround

(with the exception of

2 DBD component)

Experimental techniques


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Source = Detector

Well known Ge diodes technology

5 Ge diodes with a total statistic of 10.9 kg - ( 86%) 76Ge

The diodes mounted in copper cryostats

with copper, lead, and polyethylene shielding

The total exposure 71.7 kgyr The energy resolution about 3.5 keV at Q

(best value of all 0 experiments)

location: Underground Gran Sasso Laboratory (Italy)

Heidelberg Moscow Experiment

Operated between 1990 and 2003


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mee = 0.1 - 0.9 eV (0.44 eV)1/20 (y) = (0.69 4.81) 1025 y (1.19 1025 y)(99,9973 % c.l. 4.2 )

H.V. Klapdor-Kleingrothaus et al. NIM.A 522(2004)371

Evidence for a peak events at Q with 28.7 events

Skepticism of scientific community

Klapdor-Kleingrothaus HV hep-ph/0205228

H.L. Harney, hep-ph/0205293 Independent answers of authors

Klapdor-Kleingrothaus HV et al., NIM A510(2003)281Klapdor-Kleingrothaus et al., NIM A 522(2004)371 Other articles

Aalseth CE et al. , Mod. Phys. Lett. A 17 (2002) 1475

Feruglio F et al. , Nucl. Phys. B 637 (2002) 345

Zdezenko Yu G et al., Phys. Lett. B546(2002)206Comments and analysis HD-M data

Heidelberg Moscow Exp and the 0 claim

Not totally accepted result unrecognized peaks

dimension of analyzed energywindow

December 2001, 4 authors (KDHK) of HM collaboration claim the 0 of 76Ge


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Reduction of Bkg with Pulse Shape Analysis (PSA) (factor 5)

Multi-site events identification

(gamma bkg)

Heidelberg Moscow Exp and the 0 claim

NEMO 3 (N i E M j E i )


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NEMO 3 (Neutrino Ettore Majorana Experiment)

Other sources

100MoQ = 3034 keV

Detector: tracking detector with 7 different sources

Energy resolution: 8% @ Qvalue

Location: Modane Underground Laboratory (France)

Bckg

sources thickness mg/cm2)

82Se (0,93 kg)

Multi-source detector

The background is about 1.2x10-3 cnts/(keVkgyr)at 3 MeV

NEMO 3 (N i E M j E i )


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NEMO 3 (Neutrino Ettore Majorana Experiment)

1 Source plane

2 Tracking volume (3-D readout wire drift

chamber with 6180 cells)

3 Calorimeter volume (1940 plastic

scintillator block with PMT)


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C i i E i t


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Cuoricino Experiment

1/20 (y) > 2.81024 y (90% CL) for 130Te

Set lower limit for 0

No signal was found

This limit is not sensitive enough to scrutinize the HM result


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Running and Future

experiments

CUORE (C i U d d Ob t


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130Te

Q = 2530 keV

~ 34% natural abundance

CUORE (Cryogenic Underground Observatory

for Rare Event)

90cm

Expansion of Cuoricino

19 towers Cuoricino-like

Detector: array of 988 5x5x5 cm3 TeO2bolometers @ ~ 10 mKelvin (total

mass = 741 kg)

Energy resolution: 0.28% @ QvalueLocation: Hall A at LNGS (Italy)


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The GERDA Experiment: detector

The detectors, arranged in strings,

will be put in LAr in order to cool

down them and also shield them.


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The GERDA Experiment: setup

Ge Array

Germanium detectors

Water / Muon-Veto ()

Clean room / lock

Steel-tank + Cu l inin g

Liquid argon (ni t rogen)

- neutron moderator

- Cerenkov medium for

4p muon veto

Additional water

shielding:

GERDA goal and phases


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GERDA goal and phases

Phase II: 2013

new segmented detectors

exposure: 100 kgy

(it was 71 kgy in HM)

bkg: 10-3 count/(keV kg y)

Phase I: Started Commissioning in 20108 crystals from HM and IGEX (13 Kg)

exposure: 15 kgy

bkg: 10-2 cnt/(keV kg y)

Bkg Goal: 10-3 count/(keV kg y)

improvement of a factor 100 with respect HM

Further Possible Phase

Collaboration with Majorana Experiment to construct a single larger experiment

A preliminary result for 2 of 1/20 = 1.881021 y is reported

S NEMO


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SuperNEMO

Expansion of NEMO-3

82Se

Q = 2995 keV

Detector: tracking detector withdifferent sources

150NdQ = 3367 keV

Location: Modane (Fr) / Canfranc (SP)

5 m

1m

Top view

Tracking: drift chamber ~3000 cell (Gaiger mode)

Calorimeter: scintillators + PM ~ 1000 if sc. blocks

~ 100 scint. bars

SuperNEMO


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Improvement with respect to NEMO-3:

SuperNEMO

NEMO-3 SuperNEMO100Mo Choice of isotope 150Nd or 82Se

7 kg 100 -200 kgIsotope Mass

Efficiency8% 30%

Internal contamination208Tl < 20 mBq/Kg214Bi < 300 mBq/Kg

208Tl < 2 mBq/Kg214Bi < 10 mBq/Kg

Energy resolution8% @ 3MeV 4% @ 3MeV

SENSITIVITY1/20 (y) ~ 2 1024 y ~ 0.3 -1.3 eV

1/20 (y) ~ 1026 y ~ 50 meV


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EXO-200 (Enriched Xenon Observatory)

136Xe

Q = 2458 keV

200 kg of Xe enriched to 80% in 136

GOALS - search for 0 with competitive sensitivity

(and test the HM claim)

- measure 2 half life

- Understand the operation of a large LXe detector

Understand bkg / characterize detectors materials

Learn about large scale Xe enrichment

Understand Xe handling, purification

Detector: TPC of enriched liquid Xenon able to reconstruct the event position and topology.


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EXO-200 (Enriched Xenon Observatory)

Improve energy resolution via simultaneous collection of

ionized electrons and scintillation light


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EXO-200the LXe TPC

Teflon light reflector

APD plane

Central HV plane


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SNO


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SNO+

150Nd

Q = 3368 keVNd enriched to 56% in 150

Detector: refill SNO detector with liquidscintillator (linear alkylbenzene - LAB)

loaded at 0.1% with enriched Nd(not enough light output in SNO+ if using 1% Nd loading)

560 kg of 150Nd (compared to 37 gin NEMO-III)

En resolution: 7% @ Qvalue

Location: Sudbury (Canada)

(Present 130Te)

bkg:


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Simulation:

=150 meV

1 year of data

a liquid scintillator detector has poor

energy resolution; but enormous

quantities of isotope (high statistics)

and low backgrounds help

compensate

SNO+

- Test on stability of Nd-LAB: no

change in optical properties after > 1

year

- Small Nd-LS detector with a, , g,

source demonstrates it works as

scintillator


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The Majorana Demonstrator

76Ge

Q = 2039 keVDetector: Array of enriched (~86%) 76Ge in vacuum in a compact cryostat

made out of electro-formed copper.

Location: Sanford lab in South Dakota

Background index is about 0.001 cnts/(keVkgyr).

Shielding: Commercial copper, lead, and polyethylene

2m

Pb/Cu ShielLN

Dewar Cu

Cryostat

Lift

F t i


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Future scenarios

The future scenarios can be divided in possible steps:

I step [100-500 meV]:

to test of HM claim and to probe the QD region of neutrino massSuperNEMO, CUORE, GERDA, EXO-200, SNO++

if the neutrino mass is in this range different experiment could see it with different

isotopes. Precision measurement era for 0

II step [15-50 meV]:

to probe the IH region of neutrino mass. 1 ton scale and 10 ySuperNEMO (especially with 150Nd),

CUORE (especially if enriched), GERDA-III, SNO++ (enriched)

discovery in 3-4 isotopes is necessary to confirm the observation

III step [2-5 meV]:

For this big leap in sensitivity new approaches are required.Next generation experiments are precious for the selection of the future approaches

100 tons of isotopes

Unpredictable time scale and large investment in enrichment


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status of experimental searches for neutrinoless double beta decay

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