neutrino masses double beta decay oscillations majorana dirac
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Neutrino Masses
flavors N
h.cmmm ,...,,',.'''''' ellL RlclL
RllLl
clR
LllRllL
Dll
L2
A,Z A,Z + 2 e e
double beta decay
l lii
iU
oscillations
Majorana L0 Dirac
1) Oscillations:
2) Kinematics in weak decays:
3) 0 double beta decay:
222
2*
',
*'' 2
exp
kiik
iklkklli
kiilll
mmmE
xmiUUUUP
iik mU ,
Majorana
Dirac
iei
N
iei
iLei
N
i
Lei mUU
mUUm
1
2
1
0
Mainzfrozen T2 source, E=4.8 eV
Troitskgaseous T2 source, E=3.5 eV
Reported anomaly most likely experimentalartifact
CL) % (95eV 2.2 m
eV2.12.21.2 m
2
CL) % (95eV 2.2 m
eV2.02.52.3 m
2
187Re 187Os + e- + e E0=2.5 keV, 43 Gyr, abundance 62.8 %
Milano: 10 AgReO4 crystals (250-300 g each)
as cryogenic bolometers (T=10 mK)
E(FWHM)=28 eV at 2.5 keV
m< 21.7 eV at 90 % CL
Double Beta Decay
-
-
1 2 2) : ( , ) ( , ) A Z A Z e e ec
ec
T G E Z MGT1 22 1 2
02 2
/ ,
2
20
2
20
00
102/1
,
mMg
gMZEG
T
FA
VGT
d(n) u(p)
ece
e
W
W
d(n) u(p)
ce
L0
2 0 2) : ( , ) ( , ) A Z A Z e e
e-c
eRW
d(n)
d(n)
u(p)
u(p)
W e-eL
m
N
i
Lej
Lejj UUmm
2
1
L 2
Eee
dN dt
E0
(A,Z)
0+ (A,Z+1)
(A,Z+2)
2+
0+
E0e-e-
Popular candidates
E0 (MeV) Abundance (%)
0.187 4.27148Ca 48Ca76Ge 76Ge 2.040 7.8 82Se 82Kr 2.995 9.2
100Mo 100Ru 3.034 9.6128Te 128Xe 0.868 31.4130Te 130Xe 2.533 34.5136Xe 136Ba 2.479 8.9150Nd 150Sm 3.367 5.6
232Th 232U 238U 238Pu
0.858 1001.145 99.3
dirdirdir, geodirdir, geodir, geodir
melking
dir
Nucleus QRPA
Caltech
Shell model
Strasbourg-Madrid
exp
48Ca - 0.91 4.3 x 1019
76Ge 0.71 1.44 1.8 x 1021
82Se 1.5 0.46 8.0 x 1019
100Mo 0.6 - 1.0 x 1019
130Te 0.33 0.35 6.6 x 1020
128Te 0.27 0.25 2.0 X 1024
130Te 0.27 0.29 8.0 x 1020
136Xe <1.0 <2.6 >8.1 x 1020
pex
calc
T
T
2/1
2/1 )(22/1 yrT
pex
calc
T
T
2/1
2/1
direct
direct
geochem.
Baksan
23104.4
T1 20/ [ ] yr
( % )90 CL
m [ ]eV
QRPACaltech-Tübingen
Shell modelStrasbourg-Madrid
6.3 -
3.3 2.5
Ge76
Te130
Xe136
direct
2510)2.47.0( 25.014.0 23101.2
55.025.0
!eV5.0
?eV5.01.0|m|
Next experiments: large mass + low background, better signature, good energy resolution
NEMO 10 kg of 100Mo + … in tracking device
Majorana 500 kg of 86 % enriched 76Ge
10 cryostats with 21 crystals (2.4 kg each) , segmented readout
CUORICINO, 42kg , 760 kg 130Te, 56, 1000 crystals of TeO2, operated as
CUORE bolometers (8 mK)
GERDA 0.1, 1 t, 10 t of 76Ge crystals, immersed in lN2
EXO 200 kg, 1 t, 10 t of 136Xe in TPC
Enriched Xenon Observatory
for double beta decayAlabama, Caltech, Carleton, Colorado, UC Irvine, ITEP Moscow, Laurentian, Neuchatel, SLAC, Stanford
Ba+Ba+
system best studied (Neuhauser, system best studied (Neuhauser, Hohenstatt, Toshek, Dehmelt 1980)Hohenstatt, Toshek, Dehmelt 1980)Very specific signature “shelving” Very specific signature “shelving” Single ions can be detected from a Single ions can be detected from a photon rate of 10photon rate of 1077/s/s
22PP1/21/2
44DD3/23/2
22SS1/21/2
493nm493nm650nm650nm
metastable 47smetastable 47s
Much improved signature!
136136Xe: Xe: 136136Ba++ e- e- final state can be tagged usingBa++ e- e- final state can be tagged using optical spectroscopy optical spectroscopy (M.Moe PRC44 (1991) 931)(M.Moe PRC44 (1991) 931)
Isotopic enrichment for a gaseous substance like Xe is Isotopic enrichment for a gaseous substance like Xe is most economically achieved by ultracentrifugationmost economically achieved by ultracentrifugation
This separation step thatThis separation step thatrejects the light fractionrejects the light fractionis also very effective inis also very effective in
removing removing 8585Kr (TKr (T1/21/2=10.7 yr)=10.7 yr)that is present in the that is present in the
atmosphere from spentatmosphere from spentfuel reprocessingfuel reprocessing
Russia has enoughRussia has enoughproduction production
capacitycapacityto process 100 ton to process 100 ton
Xe and extract Xe and extract up to 10 ton up to 10 ton 136136Xe Xe
in a finite timein a finite time
Two detector options under considerationTwo detector options under consideration
High Pressure gas TPCHigh Pressure gas TPC• 5-10 atm, 50 m5-10 atm, 50 m33 modules, modules, 10 modules for 10 t10 modules for 10 t•Xe enclosed in a non-Xe enclosed in a non-structural bagstructural bag• range ~5-10cm: range ~5-10cm: can resolve 2 blobscan resolve 2 blobs•2.5m e-drift at ~250kV2.5m e-drift at ~250kV•Readout Xe scintillation withReadout Xe scintillation with WLSB (T0)WLSB (T0)•Additive gas: quenching and Additive gas: quenching and BaBa++ ++ BaBa+ + neutralizationneutralization•Steer lasers or drift Ba-ion to Steer lasers or drift Ba-ion to detection regiondetection region
Liquid Xe chamberLiquid Xe chamber•Very small detector (3mVery small detector (3m33 for for 10tons)10tons)•Need good E resolutionNeed good E resolution•Position info but blobs not Position info but blobs not resolvedresolved•Readout Xe scintillationReadout Xe scintillation•Can extract Ba from hi-density Can extract Ba from hi-density XeXe•Spectroscopy at low pressure:Spectroscopy at low pressure: 136136Ba (7.8% nat’l) different Ba (7.8% nat’l) different signature from natural Ba signature from natural Ba (71.7% (71.7% 138138Ba)Ba)•No quencher needed, No quencher needed, neutralization neutralization done outside the Xedone outside the Xe
x - yplane
anode(20 m)
potential(100 m)
grid
1 cm
liquid scintillator(veto+anti-Compton)
PMT
CF4 gasat 3 bar
acrylic vessel+field shaping rings
steel vessel
e
cathode(-45 kV)
reactor 18 m
reac
e-vD=2.3 cms
CH2+B
Pb1 m
Grenoble-Neuchâtel-Padova-Zurich (Bugey reactor)
e-, 232Th
(E)/E=3.4 % at 1.59 MeV
(E)/E= 2.7 % at 2.48 MeV
Gotthard 5 bar xenon
(from cathode), 210Po (238U chain)
quenching (/e-)=1/6.5
(E)/E=1.1 % at 2.48 MeV !
Energy resolution
/EF(E/W)E)/E(
F=0.19, W=22 eV
(E)/E=0.13 % at 2.48 MeV !
Micromegas
Woven mesh stainless steel
Neuchâtel-CERN:
CF4
1 bar 2 bar0 10 20 30 40 E(keV)
Ag
Fe
Fe
Agpulser pulser
0 10 20 30 E(keV)
Anode with spacers
Light detection (electroluminescence)in xenon (+CF4?)
Doped fibers : 1 step WLS UV (180 +/-20nm) to blue or 2 step WLS with coated fibers
e- track
Optical fibers x-y
Multianode photomultiplier
Grid (metallic cloth)
UV photons
Anode (charge)
Two gap scheme:Grid (metallic cloth)
anode
ITEP-Moscow, Kharkov, Neuchâtel
Fibers (250 m)
1 kV/cm
Found a clear (anti)correlation between ionization and scintillationFound a clear (anti)correlation between ionization and scintillation
~570 keV~570 keV
Major effort now: liquid xenon
Have demonstrated that we can get sufficient energyHave demonstrated that we can get sufficient energyresolution in LXe to separate the 2resolution in LXe to separate the 2νν from the 0from the 0νν modesmodes
We can do ionization measurements
as well as anyone
Now we turn on our newcorrelation technique…
Resolu
tions
Resolu
tions
at 5
70 keV
at 5
70 keV
3.3%@570keV3.3%@570keVor 1.6%@2.5MeVor 1.6%@2.5MeV
• Prototype Scale– 200 Kg enriched 136Xe– All functionality of EXO except Ba identification– Operate in WIPP for ~two years
• Prototype Goals– Test all technical aspects of EXO (except Ba id)– Measure 2 mode– Set decent limit for 0 mode (probe Heidelberg-
Moscow)
Massive materials qualification programled by Alabama with contributions from
Carleton, Laurentian and Neuchatel
•Approximate detector simulation with material properties to establish target activities•NAA whenever possible (MIT reactor + Alabama)•Direct Ge counting at Neuchatel, Alabama and soon Canada•High sensitivity mass spectroscopy starting in Canada•Alpha counting at Carleton and Stanford•Rn outgassing measurements starter at Laurentian (Xe plumbing)•Full detector simulation in progress
Vue-des-Alpes
400 cc germanium
Pb Plombum type VG2
0
20
40
60
80
100
120
0.00 250.00 500.00 750.00 1'000.00 1'250.00 1'500.00 1'750.00 2'000.00 2'250.00 2'500.00 2'750.00 3'000.00
Energy [keV]
Co
un
ts
Temps mesure : 1'116'322 sMasse : 34 kg
Pb Plombum VG2 13 days 34 kg
Spectre du Plomb de chez Plombum type VG2
0
0.5
1
1.5
2
2.5
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100
2601.11
2604.07
2611.61
2612.92
2613.25
2614.89
2616.86 2623.75 2625.06
2614 keV 208Tl (232Th chain)
APD plane below crossed wire array
100 APD channels (7 APD grouped together) provide light and t0
200 ionization channels (groups of wires 100 x +100 y)
Can define fiducial volume
Cryostat Cross Section
Condenser
Xenon Heater
should be
on this area
Xenon
Chamber
Outer Copper Vessel
Inner Copper Vessel
FC-87
FC-87
1” thick Thermal Insulation (MLI-vacuum), not shown to scale
Outer Door
Inner Door
Xenon
Chamber
Support
Assuming
1) that the Xe chamber + Ba tagging gives 0 background from radioactivity...2) that the energy resolution is (E)/E=2 % (2!)
Conclusion:
With a coordinated effort, the meV region is within reach!
Mass Enrichment Eff. Time Background
(kg) (%) (%) (yr) (events) (yr) QRPA SM1000 90 70 5 0.3 0.05 0.0810000 90 70 10 5.5 0.02 0.03
T1/2
0 <m> (eV) <m
> (eV)
2*1027
1.3*1028
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