Transcript Document 7343917
Future Zero-Neutrino Double Beta Decay Experiments Outline Neutrino Mass and
bb
General Experimental Issues The Matrix Elements The New Proposals
Steve Elliott, UK Forum 2003
3 Complementary Experimental Techniques
bb b
Oscil.
Absolute Mass Scale
Relative Mass Scale
Mixing Matrix Elements
CP nature of
Need all three types of experiments to fully understand the nature of the
.
Steve Elliott, UK Forum 2003
Neutrino Masses
Direct mass and
bb
experiments set absolute mass scale.
b
> < 2.2 eV The results of oscillation experiments set the relative mass scale.
Sets m
scale > 50 meV
bb
addresses Dirac/Majorana nature of
.
Steve Elliott, UK Forum 2003
n n bb
(2
) vs.
bb
(0
)
e p e p n n e e p p bb
(2
): Allowed and observed 2 nd order weak process.
bb
(0
): requires massive Majorana neutrinos even in presence of alternative mechanisms.
Steve Elliott, UK Forum 2003
Energy Spectrum for the 2 e
T wo Neutrino Spectrum Zero Neutrino Spectrum 1% resolution
(2
) = 100 *
(0
)
0.0
0.5
1.0
1.5
Sum Energy for the Two Electrons (MeV)
2.0
Endpoint Energy Steve Elliott, UK Forum 2003
bb
Decay Rates
2
G
2
M
2
2
0
G
0
M
0
2
m
2 G are calculable phase space factors.
G 0
~ Q 5 |M| are nuclear physics matrix elements.
Hard to calculate.
m
is where the interesting physics lies.
Steve Elliott, UK Forum 2003
What about mixing, m
&
bb
(0
)?
No mixing:
m
bb
3
i
1
U ei
2
m i
i m
bb
m
e
m
1 virtual
exchange
±1, CP cons.
Compare to
b
decay result: real
emission
m
b
3
i
1
U ei
2
m i
2 Steve Elliott, UK Forum 2003
Min.
bb
> as a vector sum
m
bb
U e
1 2
m
1
e i
b
U e
2 2
m
2
e i
U e
3 2
m
3
U
2 e2
m
2
bb
> is the modulus of the resultant vector in the complex plane. (In this example,
bb
> has a min . It cannot be 0.) 2
U
e3
m
3
bb
> min 2
U
e1
m
1 Figure from: PR D63, 073005
b
Steve Elliott, UK Forum 2003
More General: 3
(Inverted Heir.) 30 meV or few x 10 27 yr Plot Thanks to Petr Vogel Steve Elliott, UK Forum 2003 m smallest
More General:
(Normal Heir.) Plot Thanks to Petr Vogel 30 meV or few x 10 27 yr Steve Elliott, UK Forum 2003
Physics Reach
Normal Hierarchy m 1 ~ 0 meV m 2 ~ 7 meV m 3 ~ 55 meV
bb
> ~ 5 meV Inverted Hierarchy ~55 meV ~55 meV ~0 meV 28 or 55 meV Degenerate = M > about 100 meV M M M/2 or M Solar + KamLAND + Atmospheric (U e3 ~ 0)
m
bb
2
m
1
21
0.866
2
m
1 2
m
2 21 Steve Elliott, UK Forum 2003
An exciting time for
bb
!
For at least one neutrino:
m
bb
m
2
atmos
50 meV For the next experiments:
m
i
> 50 meV < m
bb
> in the range of 10 - 50 meV is very interesting.
Steve Elliott, UK Forum 2003
m
bb
An Ideal Experiment
Maximize Rate/Minimize Background
b
E
Mt live
1 4 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
bb
(0
) Slow
bb
(2
) rate Identify daughter Event reconstruction Nuclear theory Steve Elliott, UK Forum 2003
Classes of Background
bb
(2
) tail Need good energy resolution.
Natural U, Th in source and shielding Pure materials, identify
bb
timing, position.
daughter, pulse shape, Cosmic ray activation Store and prepare materials underground. Steve Elliott, UK Forum 2003
2.0
1.5
1.0
bb
(2
) as a Background.
Sum Energy Cut Only next generation experimental goal 30 20 10 0 0.90
1.00
K e /Q 1.10
0.5
0.0
0.0
0.2
0.4
0.6
K e /Q 0.8
Steve Elliott, UK Forum 2003 1.0
10 3 10 2
S B
m e
7
Q
2 1/ 2 0 1/ 2 6
10 1 10 0 10 -1 10 -2 10 -3 10 -4 1 2 3 Resolution (%) 100 Mo 136 Xe 76 Ge 130 Te 4 5
Natural Activity
The Problem:
(U, Th) ~ 10 10 years Target:
(
bb
(0
) ~ 10 27 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
68
Ge
From: NIM A292 (1990) 337-342.
Integral of this spectrum equals integral of this peak.
Experimental data from two 1.05 kg natural detectors
ROI
This peak decays with the right half life.
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.
Statistical contribution to uncertainty.
Matrix Element contribution to uncertainty.
Would this exclude the inverted hierarchy with small m smallest ?
Need improvement in the Theory.
Steve Elliott, UK Forum 2003
“Found” Peaks Need more than one experiment
A 2527-keV Ge-det. peak that was an electronic artifact.
A ~2528-keV Te-det. peak that was a 2
s
Statisticalflucuation.
Steve Elliott, UK Forum 2003
A Great Number of Proposed Experiments COBRA DCBA NEMO CAMEO CANDLES CUORE EXO GEM GENIUS GSO Majorana MOON Xe XMASS Steve Elliott, UK Forum 2003 Te-130 Nd-150 Mo-100, Various Cd-114 Ca-48 Te-130 Xe-136 Ge-76 Ge-76 Gd-160 Ge-76 Mo-100 Xe-136 Xe-136 10 kg CdTe semiconductors 20 kg Nd layers between tracking chambers 10 kg of
bb
isotopes (7 kg of Mo) 1 t CdWO 4 crystals Several tons CaF 2 crystals in liquid scint.
750 kg TeO 2 bolometers 1 ton Xe TPC (gas or liquid) 1 ton Ge diodes in liquid nitrogen 1 ton Ge diodes in liquid nitrogen 2 t Gd 2 SiO 5 :Ce crystal scint. in liquid scint.
500 kg Ge diodes Mo sheets between plastic scint., or liq. scint.
1.56 t of Xe in liq. Scint.
10 t of liquid Xe
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
The MOON Collaboration: H.Ejiri, Y. Itahashi, N. Kudomi, M. Nomachi, T. Shima RCNP, Osaka Univ. Japan R. Hazama, K. Matsuoka, Y. Sugaya, S. Yoshida Phys. Dept. Osaka Univ. Japan K. Fushimi, K. Ichihara, Y. Shichijo University of Tokushima, Japan P.J. Doe, V. Gehman, R.G.H. Robertson, O. E. Vilches, J.F. Wilkerson, D.I. Will CENPA, Univ. Washington Seattle, USA S.R. Elliott, LANL, USA J. Engel Univ. North Carolina, USA A. Para, FNAL, USA M. Greenfield, International Christian Univ., USA M. Finger Phys. Dept., Charles Univ., Prague, Czech Republic A. Gorin, I.Manouilov, A. Rjazantsev Inst. 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 Collaboration
C. Aalseth, F. Avignone, S.R. Elliott, H. Miley…...
MOON
is 4 experiments… 0 0.168
100 Mo 100 Tc 16 s
CC Solar
-3.034
100 Ru H. Ejiri et al. PRL
85
(2000) 2917 100 Mo bb 1.00 x 10 19 y -3.034
100 Ru bb
?
100 Mo bb 6.1 x 10 20 y 100 Ru -1.293
-1.904
MOON Overview
3.3 tons 100 Mo, 34 tons Mo Doesn’t require enriched material (but would probably want it).
Scintillator/source sandwich Position and single E
b
data play big role in
bb
(2
) and U, Th rejection. Or possibly bolometer 14% efficiency ELEGANTS is precursor.
Steve Elliott, UK Forum 2003
Detection Techniques under Consideration: • • • Scintillator Mo Foil Sandwich Mo loaded liquid scintillator Cryogenic calorimeter One possible configuration scintillator Readout fibers
1 module:
Mo foil, 6m x 6m x 0.05 gm/cm Scintillator 6m x 6m x 0.25cm 222 wavelength shifting fibers
Super module (detector)
1950 Modules 6m x 6m x 5m 34 t n Mo (3 t 100 Mo) Mo foil
Steve Elliott, UK Forum 2003
MOON Prototype
C ryogenic U nderground O bservatory for R are E vents CUORE Berkeley Firenze Gran Sasso Insubria (COMO) Leiden Milano Neuchatel U. of South Carolina Zaragoza Spokesperson Ettore Fiorini Milano Steve Elliott, UK Forum 2003
CUORE Overview
0.21 ton, 34% natural abundance 130 Te TeO 2 bolometers, 750 g crystals Doesn’t require enriched material.
1020 5x5x5 cm 3 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
Steve Elliott, UK Forum 2003
CUORE Detector
Detector Damping Suspension Dilution Unit Thermal Shields
CUORICINO IS OPERATING
FIRST PULSE.
Data runs began In Feb. 2003 Steve Elliott, UK Forum 2003
E
nriched
X
enon
O
bservatory -
EXO U. of Alabama Caltech IBM Almaden ITEP Moscow
Spokesperson Giorgio Gratta Stanford
U. of Neuchatel INFN Padova SLAC Stanford U.
U. of Torino U. of Trieste WIPP Carlsbad Steve Elliott, UK Forum 2003
EXO Overview (latter talk)
10 ton, ~70% enriched 136 Xe 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 enr Xe prototype (no Ba ID) Isotope in hand Steve Elliott, UK Forum 2003
The Majorana Project
Duke 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.
Steve Elliott, UK Forum 2003
Co-Spokespersons Frank Avignone Harry Miley
Majorana Overview
0.5 ton of 86% enriched 76 Ge 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
Steve Elliott, UK Forum 2003
Majorana Layout
b
+ 90% EC 10
%
A
Ge + fast n ->
68
Ge + X
EC 68 m 68
Ga
68
Ge
68
Zn
2.9 MeV 68 Ge is the dominate background. For 500-kg enriched detector, initially expect ~500 68 Ge decays/day.
1\2 = 288 d The naturally occurring 40 K in the human body decays at a rate of 12000 decays/second.
Steve Elliott, UK Forum 2003
bb
Why Segmentation and Pulse Shape Analysis?
b
+
b
+
g bb
is pointlike.
or Compton scattered rays deposit energy in multiple locations.
Segmentation and PSD help reduce these Backgrounds.
Steve Elliott, UK Forum 2003
Recent Crystal Packaging Test
(MEGA)
Steve Elliott, UK Forum 2003
GE rmanium NI trogen U nderground S etup 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 Spokesperson Hans Klapdor-Kleingrothaus MPI Northeastern U., Boston U. of Maryland, USA University of Valencia, Spain Texas A & M U.
GENIUS
Steve Elliott, UK Forum 2003
GENIUS Overview
1 ton, ~86% enriched 76 Ge Naked Ge crystals in LN Very little material near Ge.
1.4x10
6 liters LN 40 kg test facility is approved.
100% efficient Heid.-Moscow experiment is precursor
GENIUS
Steve Elliott, UK Forum 2003
Data Acquisition Insulation
GENIUS Layout
Clean Room Liquid Nitrogen Steel Vessel 12 m Steve Elliott, UK Forum 2003 Setup for operation of three 'naked’ Germanium detectors in liquid nitrogen.
GENIUS
20
The Controversy.
16 15 10 Locations of claimed peaks 14 12 10 8 5 6 4 2 0 2000 0 2000 2020 2060 2080 2020 2040 Energy (keV) 2060 Mod. Phys. Lett. A16, 2409 (2001) 2080 2040 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 associated with that choice.
bb
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 uncertainty Steve Elliott, UK Forum 2003
Summary of Proposals
CUORE 0.21*5*1 = 1 EXO GENIUS 6.5*10*0.7 = 45 1*2*1 = 2 MAJORANA 0.5*10*1 = 5 MOON Proposed ton-year = M * T *
Anticipated
60 meV 13 meV 20 meV 25 meV 30 meV The
bb
> 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 good possibility of reaching an interesting
bb bb
experiments have a > region.
Steve Elliott, UK Forum 2003