double beta experiment using nuclear emulsions?

Double Beta experiment Double Beta experiment using nuclear emulsions?using nuclear emulsions?

M. Dracos, Osaka, 26/05/20101

ν=?

νMarcos Dracos

IPHC/IN2P3, Université de Strasbourg

Double Beta DecayDouble Beta Decay

M. Dracos, Osaka, 26/05/20102

Double Beta DecayDouble Beta Decay

M. Dracos, Osaka, 26/05/20103

T 1/2 ~ 1019-1020 years !

Observed for: Mo100, Ge76, Se82, Cd116, Te130, Zr96, Ca48, Nd150

allowed double beta

neutrinoless double beta

dW-

W-d

u

e-

e-

u

ν_

ν_

dW-

W-d

u

e-

e-

u

ν_

ν

T1/2= F(Q,Z) |M|2 <mν>2-1

Phase space factor Nuclear matrix element

Effective mass:<mν>= m1|Ue1|2 + m2|Ue2|2.ei + m3|Ue3|2.ei

|Uei|: mixing matrix elements, and : Majorana phases

5

L=2L=0

2 electron energy (keV)

Q = Ee1 + Ee2 - 2me

Neutrino OscillationsNeutrino Oscillations

M. Dracos, Osaka, 26/05/20104

Effective mass:<mν>= m1|Ue1|2 + m2|Ue2|2.ei + m3|Ue3|2.ei

|Uei|: mixing matrix elements, and : Majorana phases

U =

Ue1 Ue2 Ue3

Uμ1 Uμ2 Uμ3

Uτ1 Uτ 2 Uτ 3

⎛

⎝

⎜⎜⎜⎜

⎞

⎠

⎟⎟⎟⎟

cij =cosθij , sij =sinθij

=c12 s12 0

−s12 c12 0

0 0 1

⎛

⎝

⎜⎜⎜

⎞

⎠

⎟⎟⎟

1 0 00 c23 s230 −s23 c23

⎛

⎝

⎜⎜⎜

⎞

⎠

⎟⎟⎟

c13 0 e−iδCP s130 1 0

−e−iδCP s13 0 c13

⎛

⎝

⎜⎜⎜

⎞

⎠

⎟⎟⎟

1 0 00 e−i /2 00 0 e−i / 2+ iδ

⎛

⎝

⎜⎜⎜

⎞

⎠

⎟⎟⎟

solar,reactors

atmospheric,accelerators

reactorsacceleratorsCP violation

Majorana phases

MNSP Matrix (Maki, Nakagawa, Sakata, Pontecorvo)

Neutrino mass hierarchyNeutrino mass hierarchy

M. Dracos, Osaka, 26/05/20105

m2

m1

2

m2

2

m3

2

Degeneratem

1≈m2≈m3» |mi-mj|

Normal hierarchym

3>>> m

2~m

1

Inverted hierarchym

2~m

1>>m

3

?

mν =ce

2cR2mν1 + se

2cR2ei mν1

2 + me2 + sR

2ei mν12 + me

2 + mAtm2

mν =ce

2cR2 mν 3

2 −me2 + mAtm

2 + se2cR

2ei mν 32 + mAtm

2 + sR2eimν 3

normal

inverted

Neutrino mass hierarchyNeutrino mass hierarchy

M. Dracos, Osaka, 26/05/20106

Goal of next generation experiments:~10 meV

Inverted hierarchy

Normal hierarchy

Degen

erat

e

Lightest neutrino (m1) in eV

| mee

| in

eV

Lower bounds!

Possible mechanisms of Possible mechanisms of Double Beta decayDouble Beta decay

M. Dracos, Osaka, 26/05/20107

Possible mechanisms of Possible mechanisms of Double Beta decayDouble Beta decay

M. Dracos, Osaka, 26/05/20108

0ν can be generated by:•exchange of light Majorana neutrinos•SUSY•LR symmetric model• …•these models are very often differentiated by the 2 electron angular distribution

where K varies from -1 to +1 according to the extension of the Standard Model

(A. Ali, A.V. Borisov, and D.V. Zhuridov, Phys. Rev. D 76, 093009 (2007))

Present detection techniques Present detection techniques or under investigation or under investigation

M. Dracos, Osaka, 26/05/20109

CalorimeterSemi-conductorsSource = detector

, E

Calorimeter(Loaded) Scintillator

Source = detector

,

Tracko-caloSource detector

isotope choice

Xe TPCSource = detector

,M

good energy resolution better background rejection

CU

OR

E

CaF2(Pure)

CA

ND

LES

NEM

O3

EX

O

Bolometers (Cuorecino)Bolometers (Cuorecino)

M. Dracos, Osaka, 26/05/201010

Double-Beta Decay in Tellurium 130

Q-value for 0νββ in 130Te

2530.3 ± 2.0 keV

Heat sink

Thermal coupling

Thermometer

Decay

Crystal absorber

•44 5x5x5 cm3 and 18 3x3x6 cm3 TeO2 crystals,

•detector mass 40.7 kg,

•130Te mass 11 kg

Candidate nuclei for double beta Candidate nuclei for double beta decaydecay

M. Dracos, Osaka, 26/05/201011

For most of thenuclei in this listthe 2νββ decayhas been observed

The NEMO3 detectorThe NEMO3 detector(Fréjus tunnel)(Fréjus tunnel)

M. Dracos, Osaka, 26/05/201012

• Calorimetry combined with electron tracking

• Advantage:• detection of the 2 electrons• background rejection

• • • • electronic noise• …

The NEMO3 detectorThe NEMO3 detector(Fréjus tunnel)(Fréjus tunnel)

M. Dracos, Osaka, 26/05/201013

Sources : 10 kg, 20 m2

wire chamber(Geiger)

3m

energy and time of flight measurements

plastic scintillator blocks

2 electron tracks

+photomultipliers (Hamamatsu 3", 5")

expected sensitivity up to mν~0.3 eV

with magnetic field

low radioactivity materials

The NEMO3 detectorThe NEMO3 detector

M. Dracos, Osaka, 26/05/201014

Sources : 10 kg, 20 m2

NEMO3 detector inside aradon tente

IsotopesIsotopes

M. Dracos, Osaka, 26/05/201015

Isotope Q (keV)

116Cd116Sn 2804.74.282Se82Kr 2995.23.3100Mo100Ru 3034.86.396Zr96Mo 3350.03.5150Nd150Sm 3367.14.948Ca48Ti 4272.04.1

Bckg

sources thickness 0 mg/cm2)

82Se (0,93 kg)

isotopes used by NEMO3 experiment at Fréjus

Event ExamplesEvent Examples

M. Dracos, Osaka, 26/05/201016

Typical ~1 MeV 2ν candidate event

Trigger•1 PMT > 150 keV•3 Geiger cells (2 neighbours + 1)•Trigger rate ~7 HzMain criteria•2 tracks with Q < 0•common vertex•internal event from the foil (TOF cut)•No unassociated PMT ( rejection)•No delayed short tracks ( rejection from 214Bi-214Po cascade)• rate: 1 event / 2.5 minutes

Event ExamplesEvent Examples

M. Dracos, Osaka, 26/05/201017

Main sources of Main sources of BackgroundBackground

M. Dracos, Osaka, 26/05/201018

Many ways to mimic a signal•Natural radioactivity

•U/Th chains (Rn),•40K

•Cosmic μ•Neutrons•Artificial radioactivity

ResultsResults

M. Dracos, Osaka, 26/05/201019

932 g389 days

2750 even.S/B = 4

82Se

82Se T1/2 = 9.6 0.3 (stat) 1.0 (syst) 1019 y

116Cd T1/2 = 2.8 0.1 (stat) 0.3 (syst) 1019 y

150Nd T1/2 = 9.7 0.7 (stat) 1.0 (syst) 1018 y

96Zr T1/2 = 2.0 0.3 (stat) 0.2 (syst) 1019 y

48Ca T1/2 = 3.9 0.7 (stat) 0.6 (syst) 1019 y

48Ca

background subtracted

Phase I + II693 days

T1/2(0ν) > 5.8 1023 (90 % C.L.) <mν> <0.6-2.5 eV

Expected in 2009T1/2(0ν) > 2 1024 (90 % C.L.) <mν> <0.3-1.3 eV

100Mo( 7 kg )

Super NEMOSuper NEMO

M. Dracos, Osaka, 26/05/201020

• Improvements:– Energy resolution 15% E/E = 4% @ 3 MeV – Efficiency 15% 20 - 40% @ 3 MeV – Source x10 larger 7kg 100 - 200 kg

• Most promising isotopes– 82Se (baseline) or perhaps– 150Nd

• Aim: T1/2 > 2 x 1026 y M < 40 - 90 meV

R&D up to 2010/2011, constructionbetween 2012 and 2014 (if approved)

source sheet

Nuclear EmulsionsNuclear Emulsions

M. Dracos, Osaka, 26/05/201021

• Compact objects ("cheap" detectors)

• Very high space accuracy (<μm)• 3D information• No need for high tech, nor super

trained staff• Very suitable for discoveries

1947 Lattes, Muirhead, Occhialini & Powell observe →μ→e in nuclear emulsions using cosmic rays (few events are significant to make a discovery)

1951

OPERA ExperimentOPERA Experiment

M. Dracos, Osaka, 26/05/201022

Pb ES ESPb

Nuclear Emulsions

θx~ 2.1 mrad x~ 0.21 μm

emulsion “grains”

track segment

50 200 50 (μm)

1 mm

~15 grains/50 μm

e, μ h

τ

ντ

νe , νμ

decay “kink”

>25 mrad

High spatial resolution is needed

(do not forget that large surfaces have to

be covered)ντνμ

M. Dracos, TAUP0923

robot

Target Tracker+ brick walls

(2x31)

ν

muon spectrometer(RPC + drift tubes)

scintillator strips

Pb/emulsion brick wall

"target" wall

brick(56 Pb/Em.)

8 cm (10X0)

150000 bricks(1.25 kt)

(full description in JINST 4, P04018 (2009))

The OPERA DetectorThe OPERA Detector

Changeable Sheet Doublet

8.3 Kg

M. Dracos, TAUP0924

The OPERA DetectorThe OPERA Detector

"Industrial" production, development, handling, scanning and analysis of emulsions.

BAM (Brick Assembling Machine)

5 articulated robots5 articulated robots

The BMS (Brick Manipulator System)

M. Dracos, TAUP0925

The OPERA emulsion The OPERA emulsion scanningscanning

Based on the tomographic acquisition of emulsion layers.Nominal scanning speed ~20 cm2/h.

~ 20 bricks daily extracted → thousands of cm2/day

Customized commercial optics and mechanics

The European Scanning System The S-UTS (Japan)

Hard coded algorithms (speed higher than 50 cm2/h)

M. Dracos, TAUP0926

The OPERA first eventThe OPERA first event

νμ μ

hadrons

W

Muon momentum: ~7.5 GeV

charged current

decay with emulsionsdecay with emulsions

M. Dracos, Osaka, 26/05/201027

e

e

"veto" emulsion,if needed

(~50 μm like in OPERA?)

plastic base "" emulsionthick enough to detect up to 4 MeV electrons (density?)

beta source(~50 μm in NEMO3

could be less for emulsions)

•J. Soc. Photogr. Sci. Technol. Japan. (2008) Vol. 71 No. 5 (http://arxiv.org/abs/0805.3061)•Radiation Measurements 44 (2009) 729–732

Tests in Nagoya using Tests in Nagoya using OPERA nuclear emulsionsOPERA nuclear emulsions

M. Dracos, Osaka, 26/05/201028

A. Ariga, diploma thesis

50 μm

electron spectrometer

Electron tracks in emulsionsElectron tracks in emulsions

M. Dracos, Osaka, 26/05/201029

1 MeV e-

2 MeV e-

(A. Ariga and NIM A 575 (2007) 466)

simulation

simulation100 μm

decay with emulsionsdecay with emulsions(comparison with NEMO3/SNEMO)(comparison with NEMO3/SNEMO)

M. Dracos, Osaka, 26/05/201030

• NEMO3 surface: 20 m2

•Super-NEMO surface: 10x20 m2

• To cover the same isotope source surface with emulsions (both sides to detect the 2 electrons) we need an emulsion surface: 2x200=400 m2.

• Just for comparison, one OPERA emulsion has a surface of about 0.012 m2 and one brick 0.680 m2. So 400 m2 is about the equivalent of 600 OPERA bricks over 150000 (but not with the same thickness of course, taking into account the thickness this could be the equivalent in emulsion volume of about 25000 OPERA bricks).

• Use the same envelops like the OPERA changeable sheets by introducing at the middle of the two emulsions (or stack of emulsion sheets) a double beta source sheet.

• Keep all these envelops for some time (e.g. 6-12 months) in the experiment and after this period start scanning them one after the other. They could be replaced by new envelops during 5 years in order to accumulate something equivalent to what Super-NEMO could do: 5*400 year*m2

• Experiment volume: <5 m3 very compact experiment!

Previous tentativePrevious tentative

M. Dracos, Osaka, 26/05/201031

• 1.28 g 96Zr (powder)• source thickness: 180 μm• total exposure time: 3717 hours• scanned surface for electron pairs: 10 mm2

• estimated total efficiency: 18%

Conclusion:• T1/2(96Zr)>1017 years,• decrease the thickness of the isotope layer,• use low radioactivity emulsions,• scanning speed has to considerably be increased

(automatic scanning needed).

Emulsion scanningEmulsion scanning

M. Dracos, Osaka, 26/05/201032

0.003

0.003

0.1

0.11.2

7.0

4060

140

700

0.001

0.01

0.1

1

10

100

1000

cm

2 /

h

TS(1994) NTS(1996) UTS(1998) SUTS(2006) SUTS(2007-)

Scanning Power Roadmap

1stage

facility

CHORUS DONUT OPERA

• How much time is needed to make a full scan of 2000 m2 (full scan in all volume not needed, just follow tracks present in the emulsion layer near the isotope foil)?

• If the Japanese S-UTS scanning system is used with a speed of 50 cm2/hour, for one scanning table: 25 m2/year (200 working days/year). By using 16 tables and extracting 100 m2/3 months (1 year exposure at the beginning and putting back new emulsions with the same isotopes), this finally will take less than 5 years (as Super-NEMO).

• Probably the emulsion thickness needed to detect these electrons will need more scanning time and the speed would be significantly less than 50 cm2/h. On the other hand, scanning speed increases with time…

Nakamura sanNufact07

Pending questionsPending questions

M. Dracos, Osaka, 26/05/201033

• Energy resolution for NEMO: 15% for 1 MeV electrons

•Required for Super-NEMO: lower than 8%

• Emulsion experiment energy resolution: ???

• Overall reconstruction efficiency for NEMO: 15-18%

•Required for Super-NEMO: >30%

• Emulsion experiment reconstruction efficiency: ?

• Minimum electron energy (~0.5 MeV?, 0.200 MeV for NEMO3), will greatly influence the total efficiency.

• Afforded background (fog)??

• Possibility to take thinner isotope sheets (60 μm for NEMO3) and have better energy resolution (but also more scanning for the same isotope mass, find good compromise).

Possible isotopes to be usedPossible isotopes to be used

M. Dracos, Osaka, 26/05/201034

For emulsions the electron detection threshold cannot be so low than NEMO3 (200 keV, low density material gas+plastic scintillator) utilisation of high Q-value isotopes>3 MeV•advantage: low background, high efficiency•problem: low abundance

Low energy cut and efficiencyLow energy cut and efficiency

M. Dracos, Osaka, 26/05/201035

• The higher the Q-value the better the detection efficiency

• For Ecut=0.5 MeV:• ECa~94%• ENd~86%• EMo~84%

• From all detection points of view 48Ca is the best, but very low abundance…

0.5 MeV seams a reachable limit, is it possible to go even lower?

light majorana neutrino model

Low energy cut and efficiencyLow energy cut and efficiency

M. Dracos, Osaka, 26/05/201036

• For this model the efficiency will be lower than the previous one

• For Ecut=0.5 MeV:• Eca~72 (94) %• ENd~54 (86)%• EMo~50 (84)%

right handed current model

(heavy majorana neutrino)

Thick Emulsions are Thick Emulsions are neededneeded

M. Dracos, Osaka, 26/05/201037

• To stop up to 48Ca isotope electrons ~5 mm thick emulsions are needed,

• A stack of 10 emulsion layers 0.5 mm thick could be used.

Feasibility studiesFeasibility studies

M. Dracos, Osaka, 26/05/201038

• Reconstruction efficiency: by counting the number of reconstructed electrons from both energy lines after scanning (this would also help to tune the algorithms).

• Electron threshold: the reconstruction efficiency for both electrons (mainly those at 482 keV) would give a good idea about the threshold.

• Energy resolution: by counting the associated grains to the track, by measuring the track range.

• Afforded background: perform the above tests with different backgrounds.

• Needed

• scanning tables,

• low radioactivity lab (Gran Sasso, Baksan, Fréjus…),

• thick emulsions (provided by Fuji?)

emulsion sheets 0.6 mm thick(3-4 layers)

207Bi source with well known activity(EICe-=976, 482 keV)

LimitationsLimitations

M. Dracos, Osaka, 26/05/201039

• high multiple scattering for low energy electrons• de/dx fluctuations• bremsstrahlung gammas (energy lost)• lost δ-electrons• electron backscattering

better to use low density emulsions?(by chance OPERA emulsions could be the best)

0.7 MeV e-

(10 tracks)

d=2.7 g/cm3

(Geant 3.2)

Extra IdeasExtra Ideas

M. Dracos, Osaka, 26/05/201040

e

e

emitter in powder (diluted in an emulsion layer ~25 μm)

better vertex and energy reconstruction?(few isotopes are anyway in powder form)

ee

decreasing density

(25 μm layers)

to minimize the emulsion thickness and better energy resolution at the end

of the track

Extra IdeasExtra Ideas

M. Dracos, Osaka, 26/05/201041

e

e

Tests of dilution of Mo powder into 75 μm nuclear emulsion

•high size granules go down during the emulsion production, but this is not a problem,

•the optical properties are not affected,

•the maximum afforded Mo density has been determined (keeping high detection efficiency).

top

bottom

(http://lanl.arxiv.org/abs/1002.2834)

M. Dracos, Osaka, 26/05/201042

Electron crossing > 4 MeV Neutron capture Electron + delay track (164 μs) 214Bi 214Po 210Pb

alpha tracks easily recognised in emulsions rejection

BACKGROUND EVENTS OBSERVED BY BACKGROUND EVENTS OBSERVED BY NEMO-3NEMO-3

which could be easily rejected in emulsionswhich could be easily rejected in emulsions

BACKGROUND EVENTS OBSERVED BY BACKGROUND EVENTS OBSERVED BY NEMO-3NEMO-3

which could be easily rejected in emulsionswhich could be easily rejected in emulsions

end of tracks easily recognised in emulsions rejection

M. Dracos, Osaka, 26/05/201043

Electron + N ’s 208Tl (E = 2.6 MeV) Electron – positron pair B rejection

no vertex or very good vertex resolution in emulsions rejection

cannot be rejected in absence of magnetic field good emulsion shielding

BACKGROUND EVENTS OBSERVED BY BACKGROUND EVENTS OBSERVED BY NEMO-3NEMO-3

and rejection in emulsionsand rejection in emulsions

BACKGROUND EVENTS OBSERVED BY BACKGROUND EVENTS OBSERVED BY NEMO-3NEMO-3

and rejection in emulsionsand rejection in emulsions

NEMO3 main background NEMO3 main background configurationsconfigurations

M. Dracos, Osaka, 26/05/201044

Proportion of types of events in raw data:

Type of event Rate (mHz)

1 e, 0 600

1 e, N 1

150

ee pairs 110

Crossing e 80

event 5.4 mHz

Emulsion R&DEmulsion R&D

M. Dracos, Osaka, 26/05/201045

done by Fuji

Tadaaki Tani (Frontier Res. Labs, FUJIFILM)

R&D to remove 40K from gelatine to decrease the fog → very promising results

ConclusionConclusion

M. Dracos, Osaka, 26/05/201046

• Technology allows today the investigation about observation of neutrinoless double beta decays using nuclear emulsions, advantages of the method:

• tracking and calorimetry,

• very high resolution detector,

• very compact volume easily shielded against external radioactivity,

• flexibility to change isotopes at any time,

• no fluids,

• cost effective technique (easy to operate).

• To prove the experiment feasibility few questions have to be answered:

• what is the energy resolution?

• what is the afforded background?

• what is the overall efficiency?

• The above questions could be answered with relatively low investment.

ENDENDENDEND

M. Dracos, Osaka, 26/05/201047

Thank you for your kind attention