Transcript Slide 1

Probing neutrinos
with 0nbb decay
Ruben Saakyan
UCL
Swansea
31 January 2006
Preview
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Neutrino oscillations, 0nbb decay and neutrino
mass
bb decay basics
Running experiments
Status of “evidence”
Future projects
Why study neutrinos?
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Essential part of the building
blocks of matter and the
Universe
Fundamental for
understanding deep
principles of nature
In Standard Model
assumed to be massless
We now know they have
non-zero mass
Neutrino mass – window
beyond Standard Model
Neutrino oscillations
Simple case: 2n vacuum oscillations
 νμ   cosθ sinθ  ν1 
 
 
 ν    sinθ cosθ  ν 
 2 
 e 
Recall that
ν i t   ν i 0e iE i t
Consider  = 45
nm
ne
nm
Oscillations  mn  0
Δm 2 L
P(ν μ  νe )  sin 2θ sin ( 1.27
)
E
2
2
from 2n to 3n oscillations
0
0  1 0
0   c13 0 s13 
 U e1 U e 2 U e 3   c12 s12 0   1

 
 
 
 

U li   U μ1 U μ 2 U μ3     s12 c12 0    0 c23 s23    0 1
0  0
1 0
U
 
0 1   0  s23 c23   0 0 e  iδ    s13 0 c13 
 τ1 Uτ 2 Uτ 3   0
where cij  cos ij , and sij  sin  ij
PMNS matrix (compare CKM matrix for quarks)
PMNS – Pontecorvo-Maki-Nakagawa-Sakata
CKM – Cabibbo-Kobayashi-Maskawa
First evidence for oscillations from
atmospheric neutrinos
SuperKamiokande detector (Japan)
Solar neutrinos
SNO – Sudbury Neutrino Observatory
Neutrino oscillation summary
Neutrino Mixing Observed !
 ne    Ue1
 nm    Um1
  
 n    U1
Ue2
Um 2
U 2
Ue3  n1  
Um 3  n2  
 
U 3  n3  
From KamLAND, solar n and atmospheric n
 0.5

U  0.61

 0.61
VERY approximately
0.87
0 

0.35 0.71

0.35 0.71
Dm2LMA ≈ 5×10-5 eV2 = (7 meV)2
Dm2atm ≈ 2.5×10-3 eV2 = (50 meV)2
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at least one neutrino with mi > 0.05 eV!
Neutrino mass.
Things we want to know.
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Relative mass scale (n-oscillations)
Mass hierarchy (n-oscillations, 0nbb)
CP-violation (n-oscillations, 0nbb
Absolute mass scale (0nbb,3H-decay, cosmology)
Dirac or Majorana particle (0nbbonly)
DL  0? Access to GUT scale (see-saw mechanism)
Important consequences for particle physics, cosmology,
nuclear physics
Theorists dream: n is Majorana particle
MR
mL
See-Saw: explains
smallness of mn
mD2
mL 
MR
M R  GUT scale Majorana mass
Leptogenesis:
may shed light on baryon
asymmetry of Universe
Standard Model 2nbb Decay
276
As
Excited state
decays possible
0+
76
Ge
Qbb
2n
1/ 2
1
2n
T (0  0 )   G ( E0 , Z ) M
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2n 2
0+
bb
2+
0+
76
Phase space ~Qbb11
|M| - NME, very hard to calculate but in case
of 2nbbcan be measured experimentally
2nbb has been observed for 10 nuclei
Se
NME
In many even-even nuclei, b decay
is energetically forbidden. This
leaves bb as the allowed decay
mode.
0nbb Decay
bb spectra. Ee1 + Ee2
DL = 2!
0n
1/ 2
1
0n
T (0  0 )   G ( E0 , Z ) M
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Phase space ~Qbb5
0n 2
 mn 2
NME
But there are other mechanisms which
could generate 0nbb (V+A, Majoron emission,
leptoquarks, extra-dimensions, SUSY, H--…)
Qbb
Effective Majorana Mass
(inverted hierarchy case)
 mn  
2
2
N
U
2
ei
mi 
i
Ue3 m3
min

U
2
ei
i
<mee>
2
2
N
Ue12 m1
Ue22 m2
b
i
e mi
Isotopes
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Best candidates:
Qbb2.038 MeV
48Ca, Q  4.272 MeV
bb
82Se, Q 2.995 MeV
bb
100Mo, Q  3.034 MeV
bb
116Cd, Q  2.804 MeV
bb
130Te, Q  2. 528 MeV
bb
136Xe, Q 2.48 MeV
bb
150Nd, Q  3.368 MeV
bb
 76Ge,
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High Qbb is important (G0n ~ Qbb5, G2n ~ Qbb11)
In most cases enrichment is a must
Different isotopes must be investigated due to
uncertainties in NME calculations !
Recent developments in NME calculations
Rodin, Faessler, Simcovic, Vogel, PRC 68 (2003) 044303
nucl-th/0503063.
Error bars are from
experimental errors on T1/2n2
Workshop on NME in
Durham, May 2005
K. Zuber, nucl-ex/0511009
 gpp fixed from experimentally measured M2n
 Different calculations converge
 Underlines the importance of 2nbb precise measurements
The Experimental Problem
( Maximize Rate/Minimize Background)
Natural Activity:
(238U, 232Th) ~ 1010 years
Target: (0nbb) > 1025 years
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Detector
Shielding
Cryostat, or other experimental support
Front End Electronics
etc.
+
Cosmic ray induced activity
Extremely radiopure materials + underground Lab
Experimental approaches to direct searches
Two approaches for the detection of the two electrons:
e-
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e-
e-

detector
source
e- detector
Source  Detector
Source  Detector
(calorimetric technique)
 scintillation
 cryogenic macrocalorimeters
(bolometers)
 solid-state devices
 gaseous detectors
high efficiency and energy resolution
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scintillation
gaseous TPC
gaseous drift chamber
magnetic field and TOF
event reconstruction
bb signature
A History Plot
Current best limit comes
from 76Ge experiments:
Heidelberg-Moscow and
IGEX
<mn> < 0.35 – 0.9 eV
mscale ~ 0.05 eV from
oscillation experiments
Hieldeberg-Moscow (Gran Sasso)
First claim (end 2001)
<mn> = 0.4 eV ???
• 5 HPGe 11 kg, 86% 76Ge
• DE/E 0.2%
• >10 yr of data taking
<mn> < 0.3 – 0.7 eV
If combine HM and IGEX
Heidelberg claim.
Recent developments
214Bi
unknown
hep-ph/0403018, NIMA, Phys. Rev…
Data analysed for 1990 – 2003
0nbb
214Bi
• Data reanalyzed with improved
binning/summing
• Peak visible
• Effect reclaimed with 4.2s
• <m> = (0.2 – 0.6) eV,
0.4 eV best fit
<m> = (0.1 – 0.9) eV (due to NME)
Personal view
71.7 kgyr
• Looks more like 2.5s of effect
•214Bi line intensities do not match
Current Experiments
NEMO-3
(Tracking calorimeter)
CUORICINO
(bolometer)
Until ~2008 results are only from these two
Sensitivity ~ 0.2 eV – 0.6 eV
Today:CUORICINO
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Located in LNGS, Hall A
CUORE R&D (Hall C)
CUORE (Hall A)
Cuoricino (Hall A)
Today: CUORICINO
2 modules, 9 detector each,
crystal dimension 3x3x6 cm3
crystal mass 330 g
9 x 2 x 0.33 = 5.94 kg of TeO2
40.7kg total
heat bath
Thermal sensor
11 modules, 4 detector each,
crystal dimension 5x5x5 cm3
crystal mass 790 g
4 x 11 x 0.79 = 34.76 kg of
TeO2
absorber
crystal
Incident
particle
Today:CUORICINO
• Operation started early 2003
• BG = 0.19 counts/kev/kg/y
• DE/E = 4 eV @ 2 MeV
mn < 0.3 – 1.6 eV (all NME)
Today: NEMO-III
AUGUST 2001
bb decay isotopes in NEMO-3 detector
bb2n measurement
116Cd
405 g
Qbb= 2805 keV
96Zr
9.4 g
Qbb= 3350 keV
150Nd
37.0 g
Qbb= 3367 keV
48Ca
7.0 g
Qbb= 4272 keV
130Te
454 g
Qbb= 2529 keV
100Mo
6.914 kg
Qbb= 3034 keV
82Se
0.932 kg
Qbb= 2995 keV
bb0n search
natTe
491 g
Cu
621 g
External bkg
measurement
(All enriched isotopes produced in Russia)
bb events selection in NEMO-3
Typical bb2n event observed from 100Mo
Transverse view
100Mo
Run Number: 2040
Event Number: 9732
Date: 2003-03-20
Vertex
emission
foil
Longitudinal
view
100Mo
foil
Geiger plasma
longitudinal
propagation
Vertex
emission
Drift distance
Deposited energy:
E1+E2= 2088 keV
Internal hypothesis:
(Dt)mes –(Dt)theo = 0.22 ns
Common vertex: Scintillator
PMT
(Dvertex) = 2.1+ mm
(Dvertex)// = 5.7 mm
Trigger:
> 150 keV
Criteria1 PMT
to select
bb events:
• 2 tracks with charge < 03 Geiger hits (2 neighbour layers + 1)
• Internal hypothesis (external event rejection)
• 2 PMT, each >
200 keV
Trigger
rate = 7 Hz• No other isolated PMT (g rejection)
• PMT-Track association
bb events: 1 event •every
1.5 minutes
No delayed
track (214Bi rejection)
• Common vertex
Latest results,
100Mo
PRL 95, 182302 (005)
T1/2 = 7.11 ± 0.02 (stat) ± 0.54 (syst)  1018 y, SSD mechanism!
T0n > 4.6  1023 y , mn< 0.7-2.8 eV
Strategy for future.
An Ideal Experiment
Large Mass (0.1t)
 bDE 
 Good source radiopurity

mn  
BG  0
 Demonstrated technology
 Mtlive 
 Natural isotope
1
 Small volume, source = detector
mn 
BG  0
Mtlive
 Tracking capabilities
 Good energy resolution or/and Particle ID
 Ease of operation
 Large Q value, fast bb(0n)
 Slow bb(2n) rate
 All requirements can NOT be
 Identify daughter
satisfied
 Event reconstruction
 Red – must be satisfied
 Nuclear theory
1
4
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A Great Number of Proposals
DCBA
Nd-150
20 kg Nd layers between tracking chambers
SuperNEMO
Se-82, Various
100 kg of Se-82(or other) foil
COBRA
CAMEO
Te-130,Cd-116
Cd-116
CdTe semiconductors
1 t CdWO4 crystals
CANDLES
Ca-48
Several tons CaF2 crystals in liquid scint.
CUORE
Te-130
750 kg TeO2 bolometers
EXO
Xe-136
1 ton Xe TPC (gas or liquid)
GEM
Ge-76
1 ton Ge diodes in liquid nitrogen
GERDA
Ge-76
0.5-1 ton Ge diodes in LN2/LAr
GSO
Gd-160
2 t Gd2SiO5:Ce crystal scint. in liquid scint.
Majorana
Ge-76
500 kg Ge diodes
MOON
Mo-100
Mo sheets between plastic scint., or liq. scint.
Xe
Xe-136
1.56 t of Xe in liq. Scint.
XMASS
Xe-136
10 t of liquid Xe
GERDA. 76Ge.
Clean room
lock
Water tank / buffer/ muon veto
Vacuum insulated
copper vessel
Liquid N/Ar
Ge Array
“Naked” 76Ge detectors in LN2/LAr
Original idea from GENIUS (Klapdor)
GERDA. 76Ge
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Phase I: collect 76Ge detectors from HM(11kg)+IGEX(8kg)
15kg[email protected] c/keV/kg/y
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sens-ty: 3·1025 y, 0.24-0.77 eV
Confirm Klapdor with 5s OR
rule out
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Phase II: increase to ~35-40 kg
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GERDA Phase I and
Phase II approved
BG < 10-3 c/keV/kg/y
within 4 yr ~ 100 kgy
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2·1026 y, 0.09-0.29 eV
Phase III: 0.5 -1 ton
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Possible merge with Majorana
>1027 y, ~ 0.03 eV- 0.09 eV
Site: Gran Sasso
Mostly European project
CUORE. 130Te
New 130Te experiment, evolution of CUORICINO
Closely packed array of 988 bolometers at 10 mK
19 towers - 13 modules/tower - 4 detectors/module
M = 741 kg ~ 265 kg of 130Te
Compact structure, ideal for active shielding
Site: Gran Sasso
Euope +US
Each tower is a CUORICINO-like detector
Special dilution refrigerator
CUORE
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Current CUORICINO background 0.2 c/keV/y/kg
Two scenarios:
I: BG down to 0.01 c/keV/y/kg
 II: BG down to 0.001 c/keV/y/kg
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Sensitivity I: 2×1026 y, 0.03 – 0.1 eV
Sensitiviry II: 6.5×1026 y, 0.017 – 0.06 eV
Approved
5 year
exposure
SuperNEMO
(UK, France, Russia, Spain, US, Czech Rep…)
Evolution of NEMO 3  same technique, larger mass, lower background
better efficiency, higher energy resolution
82Se
experiment (high Qbb, slower 2n rate) as baseline. Basic points:
Planar geometry
Modular structure
Isotope Mass 100-200 kg
Instrumentation ~20 submodules, 40,000 – 60,000 tracking channels
~ 5,000 – 20,000 PMTs (depending on the design)
Sensitivity
T1/2: 2 x1026 y
Mbb < 40 - 70 meV
SUPERNEMO. Tracking calorimeter
source
tracker
calorimeter
1m
4m
5m
Top view
Side view
Majorana.
Mostly US
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Sensitivity:
T1/2 ~ 3×1027 y
<mn> ~ 0.03 – 0.09 eV
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76Ge
0.5 ton of 86% enriched
76Ge
Very well known and
successful technology
Segmented detectors using
pulse shape discrimination
to improve background
rejection.
Prototype ready (14
crystals, 1 enriched)
Possible merger with
GERDA at later stage
Mostly US
EXO.
136Xe
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1-10 ton, ~80% enriched
136Xe
Gas TPC or LXe chamber
Optical identification of Ba
ion.
Drift ion in gas to laser
path or extract on cold
probe to trap.
200-kg enrXe prototype (no
Ba ID) being built
Isotope in hand
Sensitivity with 1 ton: 8×1026 y
0.04 – 0.08 eV
Cadmium-Telluride O-neutrino
double-Beta Research
Apparatus.
COBRA
• CdTe or CdZnTe semiconductor detectors
• Good DE/E
• Two isotopes 116Cd and 130Te
• Operate at room temperature
• New approach
Sussex
Oxford
Dortmund
Warwick
Next generation experiments
Experiment
Source and
Mass
Sensitivity
to T1/2 (y)
Sensitivity
to<mn>(eV)
GERDA/Majorana
76Ge,
500kg
3×1027
0.03 – 0.09
CUORE
$30M
130Te,
750kg(nat) 2×1026
EXO
$50M-100M
136Xe
8×1026
0.04 – 0.08
SuperNEMO
$40M
82Se(or other)
(1-2)×1026
0.04 – 0.08
$50M-100M
0.03 – 0.1
1 ton
100 kg
Plan to reach this sensitivity by ~2015
A. Giulliani, 1st Astroparticle EU town
meeting
Munich, 23-25 Nov
S[eV]
Neutrino mass scale
Expected limits from 0n-DBD
PLANCK +
larger surveys
Mb [eV]
KATRIN, MARE
S
I
N
G
L
E
b
KDHK
claim
Mbb [eV]
 inverted hierarchy will be soon
attacked
Strumia-Vissani hep-ph/0503246
 degeneracy will be deeply probed
(HM,CUORICINO, NEMO3)
CUORE, GERDA,
SUPERNEMO, ...
C
O
S
M
O
L
O
G
Y
D
O
U
B
L
E
b
Concluding Remarks
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Very exciting time for neutrino physics in general and
0nbb in particular
From oscillations: positive signal is a serious possibility
“Good value”: ~$50M for great potential scientific gain
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At least one measurement which must be done but can not
be done by any other approach (nature of n mass)
Several experiments with different isotopes are needed
(recall NME uncertainties)