Neutrino mass and neutrinoless double beta decay 0nbb

1
Neutrino mass and neutrinoless double beta decay
(0nbb)

• Ruben Saakyan
• HEP seminar
• Lancaster
• 24 October 2008

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Outline

• Neutrino mass, 0nbb and physics beyond SM
• 0nbb Experimental review
• How tos
• Current situation
• Future experiments
• Sensitivities and time scales
• Concluding remarks

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The Growing Excitement of Neutrino Physics
MINOS, MiniBOONE, etc
Neutrino Nobel Prizes 1988 1995 2002
more to come
every 7 yrs? 2009 2016 2023
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Neutrino Properties. Current Picture.
Last decade dominated by neutrino oscillation
discovery SK, 1998 then MACRO, SOUDAN2,
GALLEXSAGE, SNO, K2K, MINOS,KamLAND
Solar (SNO, SK) Reactors (KamLAND)
Reactors ( (D-)CHOOZ ) Accelerators (T2K,Nona)
DBD exprts
Atmospheric (SK) Accelerators (K2K,Minos)
UPMNS
a,b Majorana phases
q23 ? 45?
q13 lt 13?(3s) dCP Dirac phases
q12 ? 34?
From Tritium beta decay
From cosmology
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Neutrino Quest.
Neutrinos are massive and they mix
What else do we want to know?

• Number of neutrinos Are there sterile
  neutrinos?
• Absolute neutrino mass value
• Neutrino mass spectrum NH, IH or QD?
• CP-violation d ? 0,p and/or a,b ? 0,p ?
• Nature of Neutrinos Majorana or Dirac ?

addressed by 0nbb decay
Not an exhaustive list but these are the
ingredients we need to know to understand the
origin of neutrino masses in a theory BSM.
0nbb is the main focus of this talk.
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Nuclear Physics and Standard Model bb decay
For most even-even nuclei only bb decay is
possible (recall pairing term in SEMF!)

phase space
NME is measured in 2nbb
NME Nasty Nuclear Matrix Element
Measured for 10 nuclei Important input for 0nbb
NME calculation! Important to understand its
background
contribution
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Neutrinoless double beta decay
(A,Z) (A,Z2) 2 e-
DL 2 Lepton number violation!!!
(also bb and 2K-capture possible)
Light neutrino exchange
Majorana neutrino (nn)
Access to absolute neutrino mass
Other possible process VA current
ltmngt, ltlgt, lthgt Majoron emission
ltgMgt Supersymmetry l111, l113
Nuclear matrix element
Phase space factor
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ltmngt m1Ue12 m2Ue22.eia
m3Ue32.eib Uei mixing matrix elements a et
b Majorana phases
Schechter-Valle theorem bb(0n)
Majorana neutrinos
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Nature of Neutrinos.
Dirac DL 0 or Majorana DL?0
Directly related to fundamental symmetries of
particle interactions
Provides important information on origin of
neutrino mass
SEE-SAW
To obtain m3(Dm2atm)1/2, mDmt, M31015GeV
(GUT!)
Lepton number violation is one of the key
ingredients of leptogenesis as the mechanism to
generate the baryon asymmetry of the Universe.
More matter than anti-matter!
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Neutrino Mass Hierarchy.
QD would be great!
IH tough but doable
Really tough, can be 0
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bb Experimental Observables

• Observables/Signatures
• Two coincident electrons from the
• the same vertex
• Ee1 Ee2 Qbb
• Angular distribution
• Daughter nucleus ID (would be great)

Are we biasing ourselves by focusing on neutrino
mass mechanism?
Lepton Number violating parameter
could be due to
but also due to VA, Majoron, SUSY, H- or a
combination of them!
We need detectors which can probe different
mechanisms and different isotopes!
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Nuclear Matrix Elements

• A lot of progress in QRPA and SM
• Still a long way to go
• 2nbb, charge exchange, muon capture
• and other dedicated experiments
• help!

If were lucky QD mass spectrum, available
from kinematic expts. (KATRIN, MARE)
One has access to Majorana CPV phases!
but one needs reasonable NME precision to pin
them down
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The Experimental Problem( Maximize Rate/Minimize
Background)
Natural Activity t(238U, 232Th) 1010
years Target t(0nbb) gt 1025 years ? Detector Shie
lding Cryostat, or other experimental
support Front End Electronics etc. Cosmic ray
induced activity Extremely radiopure materials
underground Lab
Main threat from 214Bi (Qb 3.27 MeV) 208Tl(Qb
4.99 MeV)
0nbb is about background subtraction
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Canfranc
Going underground is a must! (reduces muon flux
by ? 105-107)
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Boulby Mine
Frejus
Canfranc
Gran Sasso
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Strategy for ideal experiment
M masse (g) e efficiency KC.L. Confidence
level N Avogadro number t time (y) NBckg
Background events (keV-1.g-1.y-1) DE energy
resolution (keV)

• Large mass
• Excellent radio-purity
• Demonstrated technology
• Enrichment feasibility
• Large Qbb value
• Slow 2nbb rate
• Identify daughter
• Good energy resolution
• Tracking capabilities
• Particle ID
• Good timing
• Detect BiPo delayed e-a decay
• Nuclear theory

the product is important when considering bkg!
Source detector (calorimeters) Great DE/E
compact
Source ? detector (foiltrackingcalorimetry) iso
tope flexibility smoking gun Topological bkg
suppression
all desirables can not be accommodated in a
single experiment
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Isotopes and enrichment
Centrifuge enrichment well established x100 kg
production possible Unfortunately not possible
for 150Nd, 48Ca, 96Zr Alternative for these
isotopes AVLIS (Atomic Vapour Laser Isotope
Separation) Interesting developments at the
MENPHIS facility in France.
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Best limits so far from Ge experiments
Experiment in Canfranc

• International Germanium EXperiment (IGEX)
• 8.9 kg y
• B 0.17 counts / kg keV y (0.10 with PSD)
• resolution 4keV !
• T0n gt 1.57 1025 y
• experiment ended 2002
• Heidelberg Moscow (HM) (2001 paper)
• 53.9 kg y 35.5 kg y with PSD
• B 0.18 counts / kg keV y (0.06 with with PSD)
• resolution 4.23 0.14 keV
• T0n gt 1.9 1025 y
• experiment ended 2003

ltmngt lt 0.4-0.6 eV
Experiment in Gran Sasso
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Are we there yet?
KKDC claim
214Bi
unknown
214Bi
0nbb?

• Full stat (71.71 kg y)
• Improved resolution 3.27 keV
• New analysis method
• A line at 2038 keV found
• I 28.75 6.86 events, 4.2s
• T1/2 (0.69-4.18) 1025 y (3s range, best fit
  1.19)

In my view can not be dismissed out of hand BUT
What else can it be?

• 56Co by cosmic rays (g 2034keV6keV X-ray)
• 76Ge(ng)77Ge (2038 keV)
• An unknown line
• A combination of the above

• Background under-estimated
• Relative intensities problem with 214Bi lines
• Unknown line in the same region

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Current data taking
CUORICINO
NEMO3
Until 2009 results form these two only Can
potentially see the KKDC effect but can not rule
it out if see nothing (recall NME)
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CUORICINO 130Te
Located in LNGS 3500 m.w.e.
Natural Te (high abundance of 130Te)
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CUORICINO Detection Principle (Bolometer)
In a monolithic thermal model thermal signal
DT E/C
The detector has to work at low temperature (10
mk) in order to develop high pulses
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CUORICINO Results
60Co sum peak 2505 keV 3 FWHM from DBD Q-value
MT 11.83 kg 130Te ? y
Bkg 0.180.02 c/keV/kg/y
Average FWHM resolution for 790 g detectors 7
keV
130Te 0nbb
t1/20n (y) gt 3.0 ? 1024 y (90 c.l.)
?Mbb? lt 0.20 0.98 eV
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NEMO3
Fréjus Underground Laboratory 4800 m.w.e.
10 kg of source 7kg 100Mo,1kg 82Se, smaller
quantities of 116Cd, 150Nd, 48Ca, 96Zr, 130Te)
All major isotopes except 76Ge and 136Xe.
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NEMO3 Detector
E1
e-
Vertex
e-
E2
Tracking detector drift wire chamber
operating in Geiger mode (6180
cells) Gas He 4 ethyl alcohol 1 Ar 0.1
H2O Calorimeter 1940 plastic
scintillators coupled to low radioactivity
PMTs B-field. Excellent particle ID e/-, g,
a
Topological signature for powerful background
rejection BDE ? 0.4 counts/kg yr
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NEMO3 Results
Unprecedented 2nbb results
T1/2 7.6 1.5 (stat) 0.8 (syst) ? 1020
y (preliminary)
T1/2(bb2n) 7.11 0.02 (stat) 0.54 (syst) ?
1018 yrs
100Mo
Long awaited 130Te result
decay to excited states
Also 2nbb measurements for 82Se,116Cd, 150Nd, 48Ca
,96Zr
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NEMO3 Results
New results reported at Neutrino08,
Christchurch, New Zealand, May08
48Ca T1/2 (2nbb) 4.4 0.5-0.4 (stat) 0.4
(syst) x 1019 y
96Zr T1/2 (2?ßß) 2.3 0.2(stat) 0.3(syst)
? 1019 y
150Nd T1/2 (2?ßß) 9.20 0.25-0.22 (stat)
0.62 (syst) x 1018 y
paper in preparation
paper in preparation
submitted to PRL
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NEMO3 0nbb Results
82Se
100Mo
T1/2 gt 5.8 1023 y ?mn? lt (0.8 1.3) eV
T1/2 gt 2.1 1023 y ?mn? lt (1.4 2.2) eV
Data until spring 2006
NEMO3 will run until mid-2010 (at least) Plan to
release new 0n results (spring06 now) by the
end of year Then one more time at the end of
experiment (2010) Expected final sensitivity
0.3-0.6 eV at 90 CL
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Future Experiments
Disclaimer Focus on next generation (100kg
isotope) experiments

• Three experiments on European Road Map
• for Astroparticle Physics (ASPERA)
• CUORE
• GERDA
• SuperNEMO

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CUORE. 130Te

• Array of 988 detectors
• 19 Cuoricino-like towers.
• M 0.741 ton of TeO2
• M 600 kg of Te
• M 203 kg of 130Te

Natural Te
90 cm
19 CUORICINO-like towers
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CUORE. 130Te

• Main background Surface contamination close to
  fiducial volume
• (Recall CUORICINO background level 0.180.02
  c/keV/kg/y)
• Two-pronged approach to tackle this background
• Passive ? surface cleaning
• Active ? event ID
• Surface sensitive bolometers
• Scintillating bolometers

Enrichment is also possible
Expected sensitivities (5 years of data)
Aggressive scenario
Baseline scenario
Nbckg0.01 cts.keV-1.kg-1.yr-1 T½ gt 2.1 1026 yr
ltmngt lt 0.03 0.17 eV
Nbckg0.001 cts.keV-1.kg-1.yr-1 T½ gt 6.6 1026 yr
ltmngt lt 0.015 0.1 eV
Planned start-up 2011
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GERDA. 76Ge
76Ge best way to check KDHK claim (free from
NME uncertainties).
Location Gran Sasso
Naked enriched (86) Ge-detectors in LAr Phased
Approach. Phase I Existing detectors
(HMIGEX) 17.9 kg enriched diodes Bkg free proble
of KKDC 10-2 cts/kg keV yr Phase II Add new
diodes (total 40kg) Bkg lt 10-3 cts/kg keV yr
Both phases funded. Under construction
Next step GERDA Majorana
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GERDA. 76Ge
PhaseI (15kg) Start data taking 2009
Phase III GERDA Majorana toward 1 ton
detector Depends heavily on background achieved
in first two phases
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SuperNEMO
Follows tried and tested technology of
NEMO3 Topological bkg rejection, isotope
flexibility (baseline 82Se and 150Nd) smoking
gun evidence (bb topology) Open-minded about
0nbb mechanism (e.g. Majoron continuum
spectrum, VA different angular
correlations)
Planar and modular
design 100 kg of enriched isotopes (20
modules x 5 kg)
1 module Source (40 mg/cm2) 4 x 3
m2 Tracking drift chamber 2000 cells in Geiger
mode Calorimeter scintillators PMTs
700 PMTs if scint. blocks
250 PMTs if scint. bars
Funded Design Study 2006-2009 Calorimeter DE/E
7/vE (MeV)? 4 at Qbb Source radiopurity 208Tl
lt ???Bq/kg,
214Bi lt 10 ?Bq/kg (if 82Se) Tracker optimization
automated wiring
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SuperNEMO
82Se sensitivity
82Se T1/2(0n) (1-2) 1026 yr depending on
exposure, background and efficiency ltmngt ? 0.04
0.11 eV (includes uncertainty in T1/2)
MEDEX07 NME 150Nd T1/2(0n) 5 1025 yr ltmngt ?
0.045 eV (but deformation not taken into
account)
Isotope flexibility Last minute
change possible if necessary (e.g. CUORE sees a
sizeable signal in 130Te

• RD Highlights
• Target DE/E reached for baseline design ? 4
  FWHM at 3 MeV (Qbb)
• 90-cell tracker prototype build and being
  commissioned
• Dedicated detector to measure foil contamination
  at mBq/kg level commissioned

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2015
Physics running
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EXO Enriched Xenon Observatory 136Xe
Liquid Xe TPC Energy measurement by ionization
scintillation Tagging of Barium ion (136Xe ?
136Ba 2 e-)
Optical spectroscopy with Ba
Ion Grabber/mover
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EXO-200
200 kg of LXe (80 enriched 136Xe in hand) No
Ba tagging Ionization scintillation to
improve DE/E and detect apha (BiPo bkg
suppression)
Being installed in WIPP (New Mexico)

• Goals
• Measure 2nbb of 136Xe
• Search for 0nbb in 136Xe with competetive
• sensitivity
• T1/20n gt 6.4 1025 y (after 2y)
• Understand the operation of a large LXe detector
• Backgrounds
• Resolution, Xe purification and handling

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Future semi conducting diodes, COBRA

• CdZnTe crystal
• several isotopes, main 116Cd
• can operate at room T
• worse resolution then in Ge but
• should be still good at Qbb(116Cd)
• detector RD, 400g (natural) prototype (LNGS)
• 400 kg (enriched) detector proposal
• resolution 1 FWHM _at_ Qbb
• B 10-3 c / kg keV y
• 5 years to reach 40-100 meV

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Great number of proposals
Matrix elements from MEDEX07 or provided by
experiments
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NEMO 3
CUORICINO, EXO-200
HM Claim
GERDA(PII)
SuperNEMO
CUORE,EXO
2020, 1t experiments ( ? 2)
gtgt2020, gt10t experiment
Next generation 100 kg expts will cover QD and
partially IH
R. Saakyan HEP Seminar, Lancaster
40
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Concluding Remarks

• Neutrino physics has made particle physics news
  in the last decade and will continue to do so in
  the future.
• The most fundamental question of lepton number
  violation (window to GUT!) and neutrino mass
  nature can only be addressed by 0nbb experiments
• Aside I would personally prefer to search for
  K-?pm-m- but where do we get so many kaons???
• A healthy and exciting experimental program
  exists. Staged approach is vital as every time
  we increase the isotope mass by x10 we bump into
  new background. E.g.
• Radon background (out-gazing) by NEMO3
• Surface contamination background by CUORICINO

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Concluding Remarks (continued)

• 0nbb experiments get big and expensive (20-50
  M for next generation)
• Coordination and collaboration are vital. Joint
  European initiatives like ILIAS is a good
  example.
• Bring together people with low-background
  expertise
• Bring together experts in nuclear structure
  calculations (NME!)
• Isotope enrichment (bank of isotopes)
• Deep purification technology
• Novel methods of bb detection and background
  suppression
• Coherent strategy for future experiments to
  reach 1-10 meV level
• Optimize number of experiments and detection
  technology.

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To find out more F.T. Avignone, S.R. Elliott,
J. Engel, nucl-ex/0708.1033
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BACKUP SLIDES
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Scintillation calorimeter, SNO

• Nd (10t) loaded in SNO detector
• signal corresponds to 0.15 eV (Nd NME w/o
  deformation!)

M.C. Chen / Nuclear Physics B (Proc. Suppl.) 145
(2005) 65
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150Nd laser enrichment (AVLIS).
AVLIS Atomic Vapor Laser Isotope Separation
Selective photoionization based on isotope
shifts in the atomic absorption optical spectra U
3 selective photons ? 235U e-

• 150Nd enrichment
• technically possible.
• MENPHIS facitlity
• (CEA/Pierrelatte France)

Depleted U collecting plate
Laser beam
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150Nd laser enrichment (AVLIS).
MENPHIS
200 kg of 2.5 enriched uranium produced

• Facility mothballed in 2003
• Principal agreement by CEA to suspend
  closure/dismantling
• 150Nd enrichment collaboration formed. SuperNEMO
  and SNO plus other interested parties
• Phased approach
• Feasibility studies for high degree enrichment (gt
  50)
• kg production and tests
• 100 kg production

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Solid Scint. Results Summary
Baseline design target! (new results- summer 2008)
Baseline design and size of single calorimeter
block
Similar result with Photonis
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How constant is the Fermi constant?
extractor and mass-spectrometer
old mineral (106 109 yr)
bb decay was first detected in geochemical
experiments (130Te?130Xe) Daughter isotope
(130Xe) extracted from an old mineral and number
of atoms counted
Geochemical (25 2) x 1020 yrs (Kirsten 83)
(27 2) x 1020 yrs (Bernatowicz 93) (8 1) x
1020 yrs (Manuel 91, Takaoka 96)
old samples (109 yrs)
young samples (few x 106 yrs)
Direct experiment (NEMO3) (7.1 0.5) x 1020 yrs
consistent with young samples
Difference between bb rates in past and present
due to time dependence of Fermi constant???
Suggestion Carry out geochemical isotope
analyses with 100Mo?100Ru, 96Zr?96Mo (daughter
not gas) etc and compare with direct
measurements.