1 TAUP - September 7, 2015 - PowerPoint Presentation

Slide1

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TAUP - September 7, 2015

S. Blot

Investigating

ββ

decay with NEMO-3 and SuperNEMO

Summer Blot, on behalf of the NEMO-3 and SuperNEMO experiments 7 September 2015

Outline

Review

of double beta decay

Recent results from NEMO

-

3

Status of

SuperNEMO

Summary

Slide2

0νββ decayBSM process that violates ΔL conversation by 2 units Can be mediated by: Light Majorana ν

, (V+A) current, SUSYObserved final state identical to 2νββ

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S. Blot

2

νββ

Arbitrary units

Σ

E

e

=

Q

ββ

0

νββ

Σ

E

e

<

Q

ββ

2

νββ decay

Occurs if β-decay is forbidden or highly suppressed (35 isotopes)2nd order weak process in the Standard Model (SM) (T½ ~1018-21 yrs) Detect 2 electrons with continuous ΣEΤΟΤ ( νe’s escape detection)

Slide3

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S. Blot

Why search for 0

νββ

decay?Observation of 0νββ decay would provide first evidence that lepton number is not conserved (LPV)Test Dirac vs Majorana nature of the neutrinoIf underlying mechanism is light Majorana neutrino exchange, can determine mass scale of neutrino

ExperimentTheoretical input

New

physics

Slide4

The NEMO-3 experiment

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S. Blot

Operated from Feb 2003–Jan 2011

Modane Underground Laboratory (LSM)Passive detector design

Source ≠ DetectorCylindrical geometry (R,φ,z)

7 different isotopes investigated

Separate tracker-calorimeter systems

Ability to reconstruct full kinematics of final state

Can disentangle underlying 0νββ

mechanisms

Measure backgrounds

in situ

Slide5

The NEMO-3 experiment

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S. Blot

Source foils

Central towerInner calo. wallOuter calo. wallTrackingvolume

φ

R

x

z

y

x

y

z

Operated from Feb 2003–Jan 2011

Modane

Underground Laboratory (LSM)

Passive detector design

Source

≠ Detector

Cylindrical geometry (R,

φ

,z)

7

different isotopes investigated

Separate tracker-calorimeter systems

Ability to reconstruct full kinematics of final state

Can disentangle underlying 0

νββ

mechanisms

Measure backgrounds in situ

Slide6

The NEMO-3 detector

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S. Blot

~10 kg of

ββ-decay isotopes100Mo,82

Se,130Tl,116Cd,150Nd,96Zr and 48Ca

Produced as

thin foils 30-60mg/cm

2

Typically 2.5 in height, 63-65 mm wide

Tracking chamber (both sides of foil)

6180

Geiger

cells (50

μ

m) operating in gas mixture of

95

%

He, 4

%

alcohol, 1

%

Ar

and 0.1

%

H2O Vertex resolution σ

XY~3 mm, σZ~10mm

Calorimeter (top, bottom, in and out)

1940 optical modules 3” and 5” PMTs coupled to polystyrene scintillator blocksσE~14-17% (FWHM), σt~250 ps (1σ) electrons @1MeV

Slide7

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S. Blot

The NEMO-3 experiment –

ββ-

decay sources

Observation of

0νββ

must be confirmed in multiple isotopes

NEMO-

3 (SuperNEMO) designed with this in mind

Largest mass with

100

Mo (6.9 kg) and

82

Se (0.93 kg)

Slide8

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S. Blot

Select events with two electrons outgoing from the foil with common vertex

Measure all relevant kinematics to reject backgrounds and investigate

0νββ topology if observed

Bcosθ

E1t

1

E2t

2l2

l

1

Mass mechanism Right-handed Current

cos

θ

between electrons

e

nergy difference between electrons (MeV)

Theoretical

Reconstructed

Theoretical

Reconstructed

Mass mechanism Right-handed Current

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

0 0.5 1 1.5 2 2.5 3

0 0.5 1 1.5 2 2.5 3

1

0.80.60.40.2

010.80.60.40.20Events10.80.60.40.20Events10.80.60.40.20The NEMO-3 experiment – Detection principle

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Backgrounds

External backgrounds from neutrons capture, producing high energy

γ-raysReduced with 4800m water equivalent overburden and extensive passive shielding (wood, iron, borated water)

Radon induced backgroundsReduced by tagging α-particles from 214Bi-214

Po cascade

Internal background decays

e.g.

Single β-decay + Møller scattering

+ conversion electron

+

γ

+ Compton scattering

2

νββ

decay

Irreducible – must measure rate with high precision

γ

γ

Internal backgrounds

External backgrounds

Use background topology to measure expected rates

Slide10

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Background channels

External background

channels (top right) identified by distinct time sequence of scintillator hits in the event (ti << tj)

Single electron channel

(bottom right

) provides channel to measure isotopes which undergo single

β

-decay

[arxiv:1506.05825]

External

e

-

γ

Single

e

-

Slide11

Latest NEMO-3 Results – 100Mo

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Best

0νββ sensitivity in NEMO-3 using 34.7 kgy

100MoNo significant excess of data over expected background in region of interest:ETOT = [2.8-3.2] MeV

Limits derived on T

½(0νββ

) for various processes

Phys. Rev D 89, 111101 (2014).[arxiv:1506.05825]

0

νββ

Mechanism

<T

1/2

x10

24

y @90% CL

Physics parameter

Mass mechanism

1.0

m

ββ

<

0.33-0.62

eV

RH current <λ>0.6<λ> < (0.9-1.3)x10-6RH current <η>

1.0<η> < (1.6-2.4)x10-8Majoron (

χ0n = 1)0.044<gee> < 1.6-4.1 x10-5<mββ> < 0.33-0.62 eV

Slide12

Comparison to other isotopes

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Most stringent half-life limit on 0

νββ with 100Mo from NEMO-3 (top)Translation into effective neutrino mass also shown (bottom)

See[arxiv:1506.05825]for references to other isotope results

Slide13

Other results from NEMO-3

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Updated results coming soon…

Best results of

2νββ T½ measurements for all 7 isotopes investigatedBest 0νββ decay limits for many as well

See backup slides for details or

J.Phys.Conf.Series

375

(2012) 042011

T

½

2

ν

(

100

Mo

)= 7.16

±

0.01

stat

±

0.54

syst

Slide14

Moving towards SuperNEMOSuperNEMO shares the same detector design principles as NEMO-3Modular in design  first module (of 20 total)

is the demonstratorDemonstrator will house 7kg of 82Se and with 2.5y will reach sensitivity of <mββ> ~ 0.2 – 0.4 eV

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FeatureNEMO-3

SuperNEMOIsotope

100Mo

82

Se (48Ca, 150

Nd)Mass7 kg100 kg

Radiopurity

A(

208

Tl) < 20

μ

Bq

/kg

A(

208

Tl) < 2

μBq/kg

(activity)A(214

Bi) < 300 μBq/kg

A(214Bi) < 10 μBq/kg

A(Rn) < 5

mBq/m3A(Rn) < 0.15 mBq/m3Efficiency18%

30%σE (FWHM@3MeV)8%4%SensitivityT1/2 > 1 x 1024T1/2 > 1 x 1026mββ < 0.3 – 0.8 eV

mββ < 0.04 – 0.1 eV*Values in table correspond to the full 20 modules of

SuperNEMO0ν0νFull SuperNEMO:mββ~ 0.04-0.1 eV

Slide15

The SuperNEMO detector

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7kg of

82Se per module (150

Nd purification studies ongoing, 48Ca also possible)Thin foils with better radiopurity

Factor of x10 decrease in

208Tl contamination and x30 decrease

in 214

Bi

Tracking chamber (both sides of foil)

Wire chamber operating in Geiger mode

Calorimeter: two main walls

5

” and 8

” PMTs coupled to

scintillator

block with optimized geometry

σ

E

~ 7.8

%

(FWHM

) for

electrons

@1

MeV

B

Slide16

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SuperNEMO

demonstrator status –

source foilsSource foil mounting test~25% of source foil produced for demonstrator (82Se)Radio-purity measurements underway using the dedicated BiPo detectorThe BiPo detector

Slide17

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Populating a C-section

Wiring robot for cell production

SuperNEMO demonstrator status – trackerFirst half of tracker complete First quarter (aka C0) commissioned, ready for shipment to LSM98.4% of cells fully operational! (504 total)Radon tests for C1 underway, commissioning to followBottom seal plate

First tracks in C0

Slide18

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SuperNEMO

demonstrator status – calorimeter

Production and testing of optical modules is well underwayEnergy resolution meeting design specifications Optical module production and testing

Slide19

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Radon emanation chamber

SuperNEMO

demonstrator status – radiopurityAll materials screened for radiopurity with HPGe detectors and radon emanation chamberRadon concentration line to measure Rn in tracker gas (Target < 0.15 mBq/m3)Preliminary measurements of radon in C-sections are very promising!!Radon centration line

Slide20

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SuperNEMO

demonstrator status – software

Many tools already implemented and validatedEvent generation and simulation of detector componentsEvent reconstruction and particle ID Improved tracking algorithmsα –particle IDAdvanced γ tracking algorithm

Slide21

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Support frame installed at LSM

C-section ready for transport to LSM

SuperNEMO demonstrator - integrationOptical module production underwaySuperNEMODemonstratorstarting to take shapeCommissioning by 2016

Slide22

Sensitivity of next generation 0νββ experiments

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<m

ββ> = |m1|Ue1|2 +m2|Ue2|2eiα + m3|Ue3|2eiβ|SNO+, SuperNEMO, CURORE< EXO+, GERDA, KAMLAND-Zen+(2017– )SNO+ ungraded, nEXO

, Super-KamLAND-Zen

P.

Guzowski

et al., Submitted to PRD (2015). arXiv:1504.03600v1 [

hep-ex]

Current best limit at m

ββ

< 130 - 310

meV

(90% CL)

Assumes

3 neutrino mixing model

Slide23

SummaryThe NEMO-3/SuperNEMO experiments offer a unique way to search for 0νββ decay and disentangle underlying mechanismsAnalysis of full data set from NEMO-3 is ongoingBest results with 100

Mo yield mββ < 0.33-0.62 eV Coming soon: new results from 82Se, 116Cd 150Nd, 96

Zr and 48Ca

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S. Blot

Thank you for your attention!

Construction of

SuperNEMO

demonstrator is well underway

Many of the most challenging design specifications have been achieved or are very close to being met

Commissioning of demonstrator should begin next year

(2016)

Goal is to reach

m

ββ

< 0.2-0.4

eV

in just

2.5

years of running

Slide24

Backup slides

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Slide25

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Dirac

vs Majorana

Schechter-Valle theoremImage from Neutrino Physics Kai Zuber, IoP Publishing 2004

Slide26

Experimental considerations for 0νββ

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DESY seminar 2015

S. Blot

Choice of isotope

Large G0ν and M0ν for shorter T1/2 Large Qββ for background rejection Large mass of isotope of interestEnrichment, purification, abundanceDetector designGood energy resolution Radio-pure materialsActive or passive

Choice of locationExperiments underground and protected bymany layers of passive and active shielding

to protect from cosmic muon

spallation, uranium fission, etc

GERDA

NEMO-3

SuperNEMO

SNO+

Slide27

NEMO-3 tracker

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DESY seminar 2015

S. Blot

Wire tracking chamber

with 6180 cells operating in Geiger mode95% He, 4% alcohol, 1% Ar

, 0.1% H2OVertex resolution: σXY ~ 3 mm, σ

Z

~ 10 mm

25 G magnetic field for discrimination between e

+/e-

Ground wire

Anode

Cathode ring

Source foil

Gaps for top/bottom calorimeter

Single tracker cell anatomy

4-2-3 layout on each side of source foil

Slide28

NEMO-3 calorimeter

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DESY seminar 2015

S. Blot

1940 optical modules

3” and 5” low-radioactivity PMTs coupled to large (10x10x10) scintillator blocks~15% / √E @ 1 MeV

Dedicated studies for PMT monitoring to ensure high quality modules used in analysis

Optical module anatomy

PMT base electronics

Magnetic shielding

Light-tight sleeve

PMT

Interface light guide

Light guide

Iron ring

Aluminized Mylar coating

Particle entrance

Scintillator block

External wall of sector

Optical

fibre

0 50 100 mm

PMT stability monitoring

Slide29

NEMO-3 calibrations

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DESY seminar 2015

S. Blot

Monthly absolute calibration runs with

207Bi sources + runs with 90Sr source for calibrating up to 3 MeVCheck PMT stability with daily laser survey (82% of PMTs stable for entire lifetime of experiment)

Laser survey validation

207

Bi

C.E. peaks

90

Sr (

90

Y)

endpoint

Slide30

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1e1

α

event displayMeasuring backgrounds: 214Bi-214Po cascadeElectronics store Geiger hits information up to 700

μs after event triggerTag 214Bi-214Po cascades with one electron and one cluster of delayed Geiger hits (α)

214

Po half-life is 164.3

μsarxiv:1506.05825

Slide31

Crossing electron

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Measuring backgrounds:

Crossing electronsHigh energy external γ-flux can produce e+e- pairs in foilUse passive shielding to reject most events (slide 9)Use calo timing information to tag and characterize external eventsNIM A 606: 449-465, 2009

Slide32

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Measuring backgrounds:

electron + gammas

Many internal background decay to excited states of their daughter isotopesTag γ rays emitted in de-excitation to identify these backgroundsChannel selectsone electron andN scintillator hitswithout tracks pointing to them100Mo 1e2γ & 1e3γ

arxiv:1506.05825

Slide33

Results from NEMO-3

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Isotope

Mass (g)2νββ T1/2 (x1019 y)0νββ T1/2 (90% CL)

Reference82Se

932

9.6 ± 0.1

stat

± 1.0syst> 3.2 x 10

23

PhysRevLett

95 (2005) 182302

150

Nd

37.0

0.91

+0.025

-0.022

stat

± 0.063

syst

> 1.8 x 10

22

PhysRevC 80 (2009) 032501

96Zr9.42.35 ± 0.14stat

± 0.16syst> 9.2 x 1021Nucl.Phys.A847 (2010) 168130Tl45470 ± 9stat ± 11syst

> 1.3 x 1022PhysRevLett 107 (2011) 062504

New results soon for 150Nd, 48Ca, 116Cd and 82Se for full exposure!

Slide34

100Mo 0νββ result

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Contribution

N2e events ETOT = [2.8-3.2] MeVExternal background< 0.2214Bi from radon5.2 ± 0.5

214Bi internal1.0 ± 0.1208Tl internal

3.3 ± 0.3

2νββ

8.45 ± 0.05

Total Expected18.0 ± 0.6

Data

15

Systematics

%

Estimation method

0

νββ

efficiency

7.0

Activity of

207

Bi calibration sources

HPGe

v NEMO

214

Bi internal

10.0Variation of activity between bkg. channels208Tl internal

10.0Activity of 232U calibration sources HPGe v NEMO

2νββ0.72νββ total energy spectrum fit > 2 MeVEvent break-downDominant systematic is absolute normalization on 0νββ efficiency