Double Beta experiment using nuclear emulsions?
description
Transcript of 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