Transcript  Neutrino Masses  

Neutrino Masses
L c
R c
L   mllD


m



m
,  , ,...
' lL l 'R 
ll ' lR l 'L 
ll 
' lL l 'R  h.c. l , l '  e



N flavors
L  2 Majorana
L  0 Dirac
 l   U li i
A,Z  A,Z + 2  e   e 
oscillations
double beta decay
i
1) Oscillations:
 mik2 x 

Pll '  U U liU l 'kU exp i
 2 E 
i ,k
mik2  mi2  mk2

*
l 'i
*
lk
2) Kinematics in weak decays: U ik , mi
 0
N
m  U eiLU eiL mi  
U U m
i 1
 i 1 ei ei i
2N
3) 0 double beta decay:


Dirac
Majorana
Mainz
frozen T2 source, E=4.8 eV
m   1.2  2.2  2.1 eV 2
m  2.2 eV (95 % CL)
Troitsk
gaseous T2 source, E=3.5 eV
m   2.3  2.5  2.0 eV 2
m  2.2 eV (95 % CL)
Reported anomaly most likely experimental
artifact
Katrin
(Karlsruhe)
E  1 eV  sensitivity  0.35 eV
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 : ( A, Z )  ( A, Z  2)  e   e    ce   ce
d(n)
u(p)
d(n)
eec
ec
eu(p)
W
W
 
2 1
T1/ 2
G
2
 E0 , Z 
2)  0 : ( A, Z )  ( A, Z  2)  e   e 
d(n)
u(p)
W
m
W
d(n)
e-
ecR
eL
eu(p)
L  0
2 2
M GT
L  2
 
0 1
T1/2 
2
2
0 gV 0
G0 E0,Z  MGT
 2 M F m 2
gA
2N
m   m jU ejLU ejL
i 1
dN
dt
0+
2
c0
0
(A,Z+1)
(A,Z)
2+
e-e-
E0
0+
(A,Z+2)
Eee
E0
E0 (MeV)
Popular candidates
48Ca
48Ca
76Ge
76Ge
82Se
82Kr
100Mo
100Ru
128Te
128Xe
130Te
130Xe
136Xe
136Ba
150Nd
150Sm
232Th
232U
238U
238Pu
Abundance (%)
4.271
2.040
2.995
3.034
0.868
2.533
2.479
3.367
0.187
7.8
9.2
9.6
31.4
34.5
8.9
5.6
dir
dir
dir, geo
dir
dir, geo
dir, geo
dir
dir
0.858
1.145
100
99.3
melking
76
Ge Heidelberg-Moscow
(Gran-Sasso)
11 kg of 87 % 76Ge in 5 crystals
Energy [keV]
0
214Bi
total 71.7 kg yr
T10/2  (0.69  4.18)  1025 yr 95 % CL!
SSE
2
direct
geochem.
direct
T1calc
/2
T1ex/ 2p
T1calc
/2
T1ex/ 2p
T12/ 2 ( yr )
Nucleus
QRPA
Caltech
Shell model
StrasbourgMadrid
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
Baksan
m [ eV]
T1/02 [ yr ]
( 90 % CL)
76
direct
Ge (0.7  4.2)  1025
130
Te  2.1 1023
136
Xe  4.4  1023
QRPA
Shell model
Caltech-Tübingen
Strasbourg-Madrid
0.14  0.25
0.25  0.55
 3.6
-
 3.3
 5.2
| m  | 0.1  0.5 eV ?
 0.5 eV!
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 decay
Alabama, Caltech, Carleton, Colorado, UC Irvine, ITEP Moscow,
Laurentian, Neuchatel, SLAC, Stanford
136Xe:
136Ba++
e- e- final state can be tagged using
optical spectroscopy (M.Moe PRC44 (1991) 931)
Much improved signature!
2P
1/2
650nm
Ba+
493nm
system best studied (Neuhauser,
Hohenstatt, Toshek, Dehmelt 1980)
Very specific signature “shelving”
Single ions can be detected from a
photon rate of 107/s
4D
2S
1/2
metastable 47s
3/2
Isotopic enrichment for a gaseous substance like Xe is
most economically achieved by ultracentrifugation
Russia has enough
production capacity
to process 100 ton
Xe and extract
up to 10 ton 136Xe
in a finite time
This separation step that
rejects the light fraction
is also very effective in
removing 85Kr (T1/2=10.7 yr)
that is present in the
atmosphere from spent
fuel reprocessing
Two detector options under consideration
High Pressure gas TPC
• 5-10 atm, 50 m3 modules,
10 modules for 10 t
•Xe enclosed in a non-structural bag
•  range ~5-10cm:
can resolve 2 blobs
•2.5m e-drift at ~250kV
•Readout Xe scintillation with
WLSB (T0)
•Additive gas: quenching and
Ba++
Ba+ neutralization
•Steer lasers or drift Ba-ion to
detection region
Liquid Xe chamber
•Very small detector (3m3 for 10tons)
•Need good E resolution
•Position info but blobs not resolved
•Readout Xe scintillation
•Can extract Ba from hi-density Xe
•Spectroscopy at low pressure:
136Ba (7.8% nat’l) different
signature from natural Ba
(71.7% 138Ba)
•No quencher needed, neutralization
done outside the Xe
Grenoble-Neuchâtel-Padova-Zurich (Bugey reactor)
liquid scintillator
(veto+anti-Compton)
CH2+B
reactor
18 m
e
steel
vessel
PMT
vD=2.3 cm/s
e-
anode
(20 m)
qreac
grid
1 cm
x-y
plane
potential
(100 m)
acrylic vessel
+field shaping rings
1m
CF4 gas
at 3 bar
cathode
(-45 kV)
Pb
M
U
N
U

-
proton
EM shower
870 keV electron
M
U
N
y
U
X,Y = 1.7mm
Z  1.7mm
20cm
z
MUNU measures qreac and Te
Energy resolution
s (E)/E  F(E/W) /E
F=0.19, W=22 eV
s(E)/E=0.13 % at 2.48 MeV !
Gotthard 5 bar xenon
e-, 232Th
 (from cathode), 210Po (238U chain)
s(E)/E=3.4 % at 1.59 MeV
quenching (/e-)=1/6.5
s(E)/E= 2.7 % at 2.48 MeV
s(E)/E=1.1 % at 2.48 MeV !
Micromegas
Woven mesh
stainless steel
Anode with
spacers
F
e
F
e
Neuchâtel-CERN:
CF4
0
10
20
1 bar
Ag
pulser
Ag
30
40 E(keV)
0
10
20
2 bar
pulser
30 E(keV)
ITEP-Moscow, Kharkov, Neuchâtel
Light detection (electroluminescence)
in xenon (+CF4?)
Grid (metallic cloth)
e- track
Multianode photomultiplier
UV photons
Anode (charge)
Two gap scheme:
Grid (metallic cloth)
Optical fibers x-y
Doped fibers :
1 step WLS UV (180 +/-20nm) to blue
or 2 step WLS with coated fibers
anode
Fibers (250 m)
Major effort now: liquid xenon
Found a clear (anti)correlation between ionization and scintillation
1 kV/cm
~570 keV
Have demonstrated that we can get sufficient energy
resolution in LXe to separate the 2ν from the 0ν modes
We can do ionization
measurements
as well as anyone
Now we turn on our new
correlation technique…
3.3%@570keV
or 1.6%@2.5MeV
Fishing ions in LXe
• 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 HeidelbergMoscow)
Massive materials qualification program
led 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
Pb Plombum VG2 13 days 34 kg
Vue-des-Alpes
Temps mesure : 1'116'322 s
Masse : 34 kg
Pb Plombum type VG2
120
400 cc germanium
100
Counts
80
60
40
20
0
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]
Spectre du Plomb de chez Plombum type VG2
2.5
2604.07
2
2614 keV 208Tl (232Th chain)
1.5
2612.92
2601.11
2611.61
2614.89
2613.25
2616.86
2623.75
1
2625.06
0.5
0
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
Detector
(356 on each side, 16 mm diameter 120 % QE in UV))
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
Drift trajectories – crossed wires
Cryostat Cross Section
Outer Door
Condenser
FC-87
Xenon
Chamber
Inner Door
Xenon Heater
should be
on this area
1” thick Thermal Insulation (MLIvacuum), not shown to scale
Xenon
Chamber
Support
FC-87
Inner Copper Vessel
Outer Copper Vessel
Full detector view
With Pb shielding
DoE’s Waste Isolation Pilot Plant (WIPP), Carlsbad NM
Assuming
1) that the Xe chamber + Ba tagging gives 0 background from radioactivity...
2) that the energy resolution is s(E)/E=2 % (2!)
Mass
(kg)
1000
10000
Enrichment Eff.
(%)
(%)
90
70
90
70
<m> (eV) <m> (eV)
Time Background T1/20
(yr)
(events)
(yr)
QRPA
SM
27
5
0.3
0.05
0.08
2*10
28
10
5.5
0.02
0.03
1.3*10
Conclusion:
With a coordinated effort, the meV region is within reach!
Status
• Enriched Xe in hand.
• Clean rooms in commercial production.
• WIPP agreement, including Environmental Impact,
complete.
• Cryostat being designed.
• Xe purification and refrigeration issues being
finalized
• Detector vessel, readout, and electronics being
engineered.