future zero-neutrino double beta decay experiments
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Steve Elliott, UK Forum 2003
Outline Neutrino Mass and General Experimental Issues The Matrix Elements The New Proposals
Future Zero-Neutrino Double Beta Decay Experiments
Steve Elliott, UK Forum 2003
3 Complementary Experimental Techniques
Absolute
Mass
Scale
Relative
Mass
Scale
Mixing
Matrix
Elements
CP
nature
of ν P Pβ P
Oscil. P P
Need all three types of experiments to fully understand the nature of the ν.
Steve Elliott, UK Forum 2003
Neutrino Masses
Direct mass and experiments set absolute mass scale.
<m> < 2.2 eV
The results of oscillation experiments set the relative mass scale.
Sets mν scale > 50 meV
addresses Dirac/Majorana nature of ν.
Steve Elliott, UK Forum 2003
(2ν) vs. (0ν)
(2ν): Allowed and observed 2nd order weak process.
(0ν): requires massive Majorana neutrinos even in presence of alternative mechanisms.
ν
νν
e
e
e
e
n
n n
np
p
p
p
Steve Elliott, UK Forum 2003
Energy Spectrum for the 2 e-
2.01.51.00.50.0Sum Energy for the Two Electrons (MeV)
Two Neutrino Spectrum Zero Neutrino Spectrum
1% resolutionΓ(2 ν) = 100 * Γ(0 ν)
EndpointEnergy
Steve Elliott, UK Forum 2003
Decay Rates
Γ2ν =G2νM2ν2
Γ0ν =G0νM0ν2mν
2
G are calculable phase space factors.G0ν ~ Q5
|M| are nuclear physics matrix elements.Hard to calculate.
mν is where the interesting physics lies.
Steve Elliott, UK Forum 2003
What about mixing, mν & (0ν)?
mββ = Uei2mi
i=1
3∑ εi
Compare to decay result: real ν emission
mβ = Uei2mi
2
i=1
3∑
virtual ν exchange ±1, CP cons.
No mixing: mββ =mνe=m1
Steve Elliott, UK Forum 2003
Min. <m> as a vector sum
mββ=Ue12m1+eiβU
e22m2+eiαU
e32m3
<m> is the modulus of the resultant vector in the complex plane.
(In this example, <m> has a min. It
cannot be 0.)
α
Ue32m3
Ue22m2
Ue12m1
<m>
min
Figure from: PR D63, 073005
Steve Elliott, UK Forum 2003
More General: 3 ν (Inverted Heir.)
30 meVor
few x 1027 yr
msmallest
<m
>
PlotThanks toPetr Vogel
Steve Elliott, UK Forum 2003
More General: (Normal Heir.)
30 meVor
few x 1027 yr
PlotThanks toPetr Vogel
Steve Elliott, UK Forum 2003
Physics Reach
Normal Hierarchy Inverted Hierarchy Degenerate
m1 ~ 0 meV ~55 meV = M > about 100 meV
m2 ~ 7 meV ~55 meV M
m3 ~ 55 meV ~0 meV M
<m> ~ 5 meV 28 or 55 meV M/2 or M
€
mββ ≈ 0.5( )2 m1 + ε21 0.866( )
2 m12 +δm21
2
Solar + KamLAND + Atmospheric (Ue3~ 0)
Steve Elliott, UK Forum 2003
An exciting time for !
< m > in the range of 10 - 50 meV is very interesting.
For the next experiments:
mββ < δmatmos2 ≈50 meV
mi > 50 meV
For at least
one neutrino:
Steve Elliott, UK Forum 2003
An Ideal ExperimentMaximize Rate/Minimize Background
Large Mass (~ 1 ton)
Good source radiopurity
Demonstrated technology
Natural isotope
Small volume, source = detector
Good energy resolution
Ease of operation
Large Q value, fast (0ν)
Slow (2ν) rate
Identify daughter
Event reconstruction
Nuclear theory
mββ ∝bΔEMtlive
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
14
Steve Elliott, UK Forum 2003
Classes of Background
(2ν) tailNeed good energy resolution.
Natural U, Th in source and shieldingPure materials, identify daughter, pulse shape, timing, position.
Cosmic ray activation Store and prepare materials underground.
Steve Elliott, UK Forum 2003
(2ν) as a Background.Sum Energy Cut Only
next generationexperimentalgoal
10-4
10-3
10-2
10-1
100
101
102
103
<m
> ( )Sensitivity meV
54321 (%)Resolution
100Mo
136Xe
76Ge
130Te
SB=me7Q
τ1/22ν
τ1/20ν δ6
2.0
1.5
1.0
0.5
0.01.00.80.60.40.20.0
Ke/Q
30
20
10
0
1.101.000.90Ke/Q
Steve Elliott, UK Forum 2003
Natural Activity
The Problem:
(U, Th) ~ 1010 years
Target: ((0ν) ~ 1027 years
Detector
Shielding
Cryostat, or other experimental support
Front End Electronics
etc.
Steve Elliott, UK Forum 2003
Cosmic Ray Induced Activity
Material dependent.
Need for depth to avoid activation.
Need for storage to allow activation to decay.
Steve Elliott, UK Forum 2003
Evidence of 68GeFrom: NIM A292 (1990) 337-342. Experimental data from
two 1.05 kg natural detectorsIntegral of this
spectrum equals integral of this
peak.
Integral of this spectrum equals integral of this
peak.
This peak decays with the right half
life.
This peak decays with the right half
life.
ROI
Steve Elliott, UK Forum 2003
Matrix Elements
There are many calculations.
Most authors quote mass limits derived from all or at least representatives of the
whole range.
How do we interpret the uncertainty associated with the mass due to the
nuclear physics?
Steve Elliott, UK Forum 2003
Consider a 100 meV result.
Matrix Elementcontribution to uncertainty.
Need improvement in the Theory.
Would this exclude the inverted hierarchy with small msmallest?
Statistical contributionto uncertainty.
Steve Elliott, UK Forum 2003
“Found” PeaksP
R D
45, 2
548
(199
2)
A 2527-keV Ge-det. peak that was an electronic artifact.
A ~2528-keV Te-det. peak that was a 2Statisticalflucuation.
NP
B35
(P
roc.
Su
pp
.), 3
66 (
1994
).
Need more thanone experiment
Steve Elliott, UK Forum 2003
A Great Number of Proposed Experiments
COBRA Te-130 10 kg CdTe semiconductors
DCBA Nd-150 20 kg Nd layers between tracking chambers
NEMO Mo-100, Various 10 kg of isotopes (7 kg of Mo)
CAMEO Cd-114 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
GENIUS Ge-76 1 ton Ge diodes in liquid nitrogen
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
Steve Elliott, UK Forum 2003
Potential Large-Mass (~1 ton) Future Experiments
Experiments in Europe
CUORE, GENIUS
NUSEL Candidates
EXO*, MAJORANA, MOON
Smaller Mass and Development Experiments Cobra*, DCBA, NEMO*, CAMEO, CANDLES, GSO…
Steve Elliott, UK Forum 2003
H.Ejiri, Y. Itahashi, N. Kudomi, M. Nomachi, T. ShimaRCNP, Osaka Univ. Japan
R. Hazama, K. Matsuoka, Y. Sugaya, S. YoshidaPhys. Dept. Osaka Univ. Japan
K. Fushimi, K. Ichihara, Y. ShichijoUniversity of Tokushima, Japan
P.J. Doe, V. Gehman, R.G.H. Robertson, O. E. Vilches, J.F. Wilkerson, D.I. WillCENPA, Univ. Washington Seattle, USA
S.R. Elliott, LANL, USA
J. EngelUniv. North Carolina, USA
A. Para, FNAL, USA
M. Greenfield,International Christian Univ., USA
M. FingerPhys. Dept., Charles Univ., Prague, Czech Republic
A. Gorin, I.Manouilov, A. RjazantsevInst. High Energy Physics, Protvino, Russia
K. Kuroda, P. Kavitov, V. Vatulin,VNIIEF, Sarov, Russia
V. Kekelidze, V. Kutsalo, G. Shirkov, A. Sisakian, A. Titov, V. Voronov,
JINR, Dubna, Russia
In Association with:
The Majorana CollaborationC. Aalseth, F. Avignone, S.R. Elliott, H. Miley…...
The MOON Collaboration:
Steve Elliott, UK Forum 2003
100Mo
100Mo
100Mo
100Tc
100Ru
100Ru
100Ru
00.168
-3.034
MOON is 4 experiments…
-1.904
CC Solar ν
H. Ejiri et al. PRL 85 (2000) 2917
1.00 x 1019 y
6.1 x 1020 y
16 s-3.034
Hamish Robertson APS, April 5, 2003
?-1.293
Steve Elliott, UK Forum 2003
MOON Overview
3.3 tons 100Mo, 34 tons Mo
Doesn’t require enriched material (but would probably want it).
Scintillator/source sandwich
Position and single E data play big role in (2ν) and U, Th rejection. Or
possibly bolometer
14% efficiency
ELEGANTS is precursor.
Steve Elliott, UK Forum 2003
• Scintillator Mo Foil Sandwich• Mo loaded liquid scintillator• Cryogenic calorimeter
One possible configurationscintillator
Mo foilReadout fibers
1 module:Mo foil, 6m x 6m x 0.05 gm/cmScintillator 6m x 6m x 0.25cm 222 wavelength shifting fibers
Super module (detector)1950 Modules6m x 6m x 5m34 t nMo (3 t 100Mo)13600, 16-anode PMT readout
Detection Techniques under Consideration:
Steve Elliott, UK Forum 2003
MOON Prototype
Steve Elliott, UK Forum 2003
Cryogenic Underground Observatory for Rare Events - CUORE
Berkeley
Firenze
Gran Sasso
Insubria (COMO)
Leiden
Milano
Neuchatel
U. of South Carolina
Zaragoza
SpokespersonEttore Fiorini
Milano
Steve Elliott, UK Forum 2003
CUORE Overview
0.21 ton, 34% natural abundance 130Te
TeO2 bolometers, 750 g crystals
Doesn’t require enriched material.
1020 5x5x5 cm3 crystals
25 towers of 10 layers of 4 crystals
Gran Sasso Laboratory
CUORICINO is an approved prototype (1 tower).
CUORICINO began operation in Feb. 2003
Steve Elliott, UK Forum 2003
CUORE Detector
Detector Damping Suspension
Dilution Unit
ThermalShields
Steve Elliott, UK Forum 2003
CUORICINO IS OPERATING
FIRST PULSE.
Data runs began In Feb. 2003
Steve Elliott, UK Forum 2003
Enriched Xenon Observatory - EXO
U. of Alabama
Caltech
IBM Almaden
ITEP Moscow
U. of Neuchatel
INFN Padova
SLAC
Stanford U.
U. of Torino
U. of Trieste
WIPP Carlsbad
SpokespersonGiorgio Gratta
Stanford
Steve Elliott, UK Forum 2003
EXO Overview (latter talk)
10 ton, ~70% enriched 136Xe
70% effic., ~10 atm gas TPC or LXe chamber
Optical identification of Ba ion.
Drift ion in gas to laser path
or extract on cold probe to trap.
TPC performance similar to that at Gottard.
100-kg enrXe prototype (no Ba ID)
Isotope in hand
Steve Elliott, UK Forum 2003
The Majorana ProjectDuke U.
North Carolina State U.
TUNL
Argonne Nat. Lab.
JINR, Dubna
ITEP, Moscow
New Mexico State U.
Pacific Northwest Nat. Lab.
U. of Washington
LANL
LLNL
U. of South Carolina
Brown
Univ. of Chicago
RCNP, Osaka Univ.
Univ. of Tenn.
Co-SpokespersonsFrank Avignone
Harry Miley
Steve Elliott, UK Forum 2003
Majorana Overview
0.5 ton of 86% enriched 76Ge
Segmented detectors using pulse shape discrimination to improve background
rejection.Prototype ready to go this fall/winter. (14
crystals, 1 enriched)
100% efficient
Can do excited state decay.
IGEX is precursor
Steve Elliott, UK Forum 2003
Majorana Layout
Steve Elliott, UK Forum 2003
AGe + fast n -> 68Ge + X
68Ge is the dominate background.
For 500-kg enriched detector, initiallyexpect ~500 68Ge decays/day. 1\2 = 288 d
The naturally occurring 40K in the humanbody decays at a rate of 12000 decays/second.
271 d68 m
+ 90% 10EC %
EC
68Ge68Ga
2.9 MeV68Zn
288d
Steve Elliott, UK Forum 2003
Why Segmentation and Pulse Shape Analysis?
+ is pointlike.+ or Compton scattered rays deposit energy in
multiple locations.
Segmentation and PSDhelp reduce these
Backgrounds.
Steve Elliott, UK Forum 2003
Recent Crystal Packaging Test (MEGA)
Steve Elliott, UK Forum 2003
GErmanium NItrogen Underground Setup - GENIUS
MPI, Heidelberg
Kurchatov Inst., Moscow
Inst. Of Radiophysical Research, Nishnij Novgorod
Braunschweig und Technische Universität, Braunschweig
U. of L'Aquila, Italy
Int. Center for Theor. Physics, Trieste
JINR, Dubna
Northeastern U., Boston
U. of Maryland, USA
University of Valencia, Spain
Texas A & M U.
SpokespersonHans Klapdor-Kleingrothaus
MPI
GENIUS
Steve Elliott, UK Forum 2003
GENIUS Overview
1 ton, ~86% enriched 76Ge
Naked Ge crystals in LN
Very little material near Ge.
1.4x106 liters LN
40 kg test facility is approved.
100% efficient
Heid.-Moscow experiment is precursorGENIUS
Steve Elliott, UK Forum 2003
GENIUS Layout
GENIUS
DataAcquisition
Clean Room
LiquidNitrogen
Insulation
SteelVessel
12 m
Setup for operation of three 'naked’ Germanium detectors in liquid nitrogen.
Steve Elliott, UK Forum 2003
The Controversy.
Locations of claimed peaks
20
15
10
5
0
Counts
20802060204020202000
Energy (keV)
16
14
12
10
8
6
4
2
0
Counts
20802060204020202000
Energy (keV)
If one had to summarize the controversy in a short statement:Consider two extreme background models:
1. Entirely flat in 2000-2080 keV region.2. Many peaks in larger region, only peak in small region.
These 2 extremes give very different significances for peak at 2039 keV.KDHK chose Model 2 but did not consider a systematic uncertaintyassociated with that choice.
Mod. Phys. Lett. A16, 2409 (2001)
Steve Elliott, UK Forum 2003
Summary of ProposalsProposed ton-year
= M * T * Anticipated<mee>, (QRPA )
CUORE 0.21*5*1 = 1 60 meV
EXO 6.5*10*0.7 = 45 13 meV
GENIUS 1*2*1 = 2 20 meV
MAJ ORANA 0.5*10*1 = 5 25 meV
MOON 3.3*3*0.14 = 1.4 30 meV
The <m> limits depend on background assumptions and matrix elements which vary from proposal to proposal.
Steve Elliott, UK Forum 2003
Conclusions
Research and Development are needed for all the future proposed detectors.
UG Lab space will be needed for some of that R&D.
The next generation experiments have a good possibility of reaching an interesting
<m> region.
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