Transcript Slajd 1 - Warszawska Grupa Neutrinowa

Neutrino masses
Determination of absolute mass scale with
beta decays:

single beta decays: energy spectra

search for neutrinoless double beta decays
2
0
The latter is extremely important in order to
understand the Universe and sources of particle masses
1
Neutrino (mass)2 spectrum
3
sin2 13
2
2

m
} sol
1
2
matm
or
(Mass)2
2
2
matm
2

m
} sol
1
3
sin2 13
Normal
Inverted
2
2
 msol
 8g105 eV2  matm
 2.5g103 eV2
 e Uei
2
  U i
2
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  U i
2
2
Various and complementary ways
to measure neutrino mass
Cosmology
Oscillation
  m1  m2  m3
2 0
Beta decay
m 
3
U
 mij2  mi2  m2j
2
ei
2
i
m
i 1
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m 
3
2
U
 ei  mi
i 1
3
Three roads to neutrino masses
4
Direct measurements of neutrino
masses


 e: tritium  decay
3
3:
H

H
e
+
e

m

2
.
2
e
V
e
e
e
3
U
 m

m

i
i
1
2 2
i
  :  decay






+
:


m

1
7
0
k
e
V
  decay





:

+
5
m

1
8
M
e
V
Information from the end of the energy spectrum.
„Mass” of flavor α – combination of mass states.
Very high precision of measurements needed.
Up to now only limits.
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m 
3
2
U
m
 i i
2
i 1
5
β-decay and neutrino mass
Model independent neutrino mass from ß-decay kinematics

experimental observable is m 2
H

H
e
+
e

e
3
E0 = 18.6 keV
T1/2 = 12.3 y
3
-
ß-source requirements :
- high ß-decay rate (short
t1/2)
- low ß-endpoint energy E0
- superallowed ß-transition
- few inelastic scatters of ß‘s
ß-detection requirements :
- high resolution (E< few eV)
- large solid angle  :6 2
- low background
History of tritium measurements
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Electrostatic filter with magnetic
adiabatic collimation
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Status of previous tritium
measurements
Mainz & Troitsk have reached their intrinsic limit of sensitivity
Troitsk
Mainz
windowless gaseous T2 source
quench condensed solid T2 source
analysis 1994 to 1999, 2001
analysis 1998/99, 2001/02
both experiments now used for systematic investigations
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Designing a next-generation
experiment
experimental observable in ß-decay is mν2
aim :
improve m by one order of magnitude (2 eV  0.2 eV )
requires : improve m2 by two orders of magnitude (4 eV2  0.04 eV2 )
problem : count rate close to ß-end point drops very fast (~E3)
• improve statistics :
- stronger tritium source (factor 80) (& large analysing plane, Ø=10m)
- longer measuring period (~100 days  ~1000 days)
L=23 m
• improve energy resolution :
- large electrostatic spectrometer with E=0.93 eV (factor 4 improvement)
- reduce systematic errors :
- better control of systematics, energy losses (reduce to less than 1/10)
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Katrin
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KATRIN will reach a final sensitivity of 200 meV
at 90\% C.L. on the absolute neutrino mass scale.
KATRIN experiment
Karlsruhe Tritium Neutrino
Experiment
TLK
at Forschungszentrum Karlsruhe
unique facility for closed T2 cycle:
Tritium Laboratory Karlsruhe
~ 75 m linear setup with 40 s.c. solenoids
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Transport of KATRIN
Complicated transport of the spectrometer in Dec. 2006
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KATRIN sensitivity
sensitivity optimisation: LoI (2001)  reference design (2004)
• improved statistics: source luminosity,
scanning
-
• reduced systematics: ß-energy losses in
source
improved sensitivity
sensitivity (90% CL)
m(ν) < 0.2 eV
discovery potential
m(ν) = 0.35 eV (5σ)
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Search for neutrinoless double
beta decays
• Why so important?
• What it would tell us (if seen)?
Reminder:
• Leptons are (mostly) left handed
2
0
1
• Anti-leptons are (mostly) right handed
•
v
 L   1  vc

1
2
c
1
v
 R   1  vc

1
2
c
Contribution of states with
2
v m
„wrong helicity” is proportional to: 1  2
c 2E
 for m=0 particle – no such
contribution
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Dirac neutrino vs Majorana neutrino
Majorana particles
Dirac particles
C
P
T






L
R
L
R






Spinor is fermion representation
(in Dirac equation)
For particles with m=0 reduces to
2 non-zero states
Special case: particle is it’s own
anti-particle

Lorentz
Boost,
E, B
 
 
 
L
R
 L
 0

 0

 R






C
P
T
only neutral particles
are candidates for beeing
Majorana particle
Example of such is 0
Double beta decays
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Double Beta Decay Candidates
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Phenomenology of 0  and 2 
• pairing interaction between nucleons (even-even nuclei more bound
than the odd-odd nuclei)
• e.g. 136Xe and 136Ce are stable against  decay, but unstable
against  decay ( for 136Xe and  for 136Ce)
odd-odd
even-even
m(A,Z) > m(A,Z+2)
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Phenomenology of 0  and 2 
1
11
GT

G
(Q
,Z)

M
2

2
2
T1/ 2
1
5
GT 2
 G0 (Q , Z)  M 0  m
0
T1/2
2
Phase space
(very well known)
Nuclear matrix element (NME)
(challenging to calculate)
2 i *
m  m1 Ue1  m2 Ue2 e
2
2 i * 2i
 m3 Ue3 e
 *,  *  linear combinations of Majorana phases  and 
20
2
Neutrino mixing and oscillations
ν  U U U ν 
1 e
2 e
3 1
 e  e
ν U U U ν 
1 μ
2 μ
3 2
μ
 μ
 
ν
ν  U U U 
1 τ
2 τ
3 3
 τ  τ
mass
eigenstates
weak
eigenstates
Pontecorvo – Maki – Nakagawa - Sakata (PMNS) matrix
3 mixing angles + 1 phase
c

s

cs c s
(

c
o
s
,








s
i
n
)
i
j
i
j
i
j
i
j

1

3 1
31
1
21
2 1



U
sc
1
cs

 e

1
2
1
2
2
32
3



s
c
e

1
sc


1
3 1
3 2
3
2
3

Majorana








Solar








i



e



Atmospheric
Reactor
i

e











Atmospheric
i
i
Phases
only 0 
ν21
Candidate Nuclei for Double Beta Decay
Q (MeV)
Abundance(%)
48Ca→48Ti
4.271
0.187
76Ge→76Se
2.040
2.995
7.8
9.2
3.350
3.034
2.013
2.8
9.6
11.8
136Xe→136Ba
2.802
2.228
2.533
2.479
7.5
5.64
34.5
8.9
150Nd→150Sm
3.367
5.6
82Se→82Kr
96Zr→96Mo
100Mo→100Ru
110Pd→110Cd
116Cd→116Sn
124Sn→124Te
130Te→130Xe
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Electron spectrum from double
 decays
•Missing
energy
•Energy
resolution
•High rates
capabilities
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 history
 1935 - (2 ) rate first calculated by Maria Goeppert-Mayer
 1937 - Majorana proposes his theory of two-component neutrino
 
 1987 – Direct laboratory evidence for 2νββ:
S. Elliot et al., Phys. Rev. Lett. 59, 2020, 1987

Direct evidence for two-neutrino double-beta decay in 82Se
 Why it took so long? Background
while signal:
1/2(U, Th) ~ 1010 years
1/2(2νββ) ~ 1020 years
 But next we want to look for a process with:
1/2(0νββ) ~ 1025-27 years
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 history
 2004 – controversial claim of observation of 0νββ:
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Experiments with active targets
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76Ge
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spectrum
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76Ge
spectrum with a possible 0νββ peak
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76Ge
spectrum with a possible 0νββ peak
76Ge
Exposure
(total):
71.7 kg.y
Clearly this needs to
be verified...
30
New experiment with Ge: GERDA
To check the questionable result – new experiment with Ge is prepared
GERDA (with contribution from Jagiellonian Uniw.), the background
reduction will be better …
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Experimental techniques
Calorimeter
Source=detector
Resolution, efficiency
Main features:
Tracking and calorimeter
Source ≠ detector
TPC (Xe)
Efficiency, Mass
Main features:
High energy resolution
Modest background rejection
 
Background, isotope choice
High background rejection
Modest energy resolution
 
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Separation of  from 2 
 spectrum
(5% FWHM)
(normalized to 10-6)
2 spectrum
(normalized to 1)
E1 + E2 (normalized to Q)
 spectrum
(5% FWHM)
(normalized to 10-2)
from S. Elliott and P. Vogel
Energy resolution is essential
F. T. Avignone, G. S. King and Yu. G. Zdesenko,
``Next generation double-beta decay experiments:
Metrics for their evaluation,’’ New J. Phys.
7, 6
33
(2005).
NEMO-3 detector
Fréjus Underground Laboratory :
4800 m.w.e.
Source: 10 kg of ββ isotopic foils
20 sectors
area = 20 m2, thickness ~ 60 mg/cm2
Tracking detector:
drift wire chamber operating (9 layer
in Geiger mode (6180 cells)
Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H2O
Calorimeter:
3m
1940 plastic scintillators
coupled to low radioactivity PMTs
B (25 G)
Magnetic field:
25 Gauss
Gamma shield: pure iron (d = 18cm)
Neutron shield: 30 cm water (ext. wall)
40 cm wood (top and bottom)
(since March 2004: water  boron)
Particle ID: e, e, and 
34
NEMO-3 detector
Fréjus Underground Laboratory : 4800 m.w.e.
Source: 10 kg of isotopic foils
area = 20 m2, thickness ~ 60 mg/cm2
Tracking detector:
drift wire chamber operating (9 layer
in Geiger mode (6180 cells)
Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H2O
Calorimeter:
1940 plastic scintillators
coupled to low radioactivity PMTs
Magnetic field:
Gamma shield:
25 Gauss
pure iron (d =
18cm)
Neutron shield:
water (ex
40 cm wood (t
30 cm
bottom)
(since March 200
35
water  boron)
decay isotopes NEMO-3
2 measurement
116Cd
405 g
Q= 2805 keV
96Zr
9.4 g
Q= 3350
keV
150Nd 37.0
g
Q= 3367
keV
48Ca
7.0
g
Q= 4272 keV
130Te
454 g
Q= 2529 keV
100Mo
6.914 kg
82Se
Q= 3034 keV
 search
0.932 kg
Q= 2995 keV
natTe
491 g
Cu
621 g
External bkg
measurement
(All enriched isotopes produced in Russia)
36
PMTs
Cathod rings
Wire chamber
Calibration tube
scintillators
 isotope
foils
37
ββ events in NEMO-3 experiment
Typical 2 event observed from 100Mo
Side view
Top view
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During installation AUGUST 2001
39
Laboratoire Souterrain de Modane
FRANCE
ITALIE
4700 m.w.e
COMMISSARIAT À L’ÉNERGIE ATOMIQUE
DIRECTION DES SCIENCES DE LA MATIÈRE
Altitudes
Distances
1228 m
0 m
1263
6210
m
m
1298
m
12 868
m
Built for aup experiment (proton decay) in 19811982
40
100Mo
ββ2ν results
(Data Feb. 2003 – Dec. 2004)
Angular Distribution
Sum Energy Spectrum
NEMO-3
100Mo
219 000 events
6914 g
389 days
S/B = 40
100Mo
•
•
Data
ββ2ν
Monte Carlo
Background
subtracted
219 000 events
6914 g
389 days
S/B = 40
NEMO-3
Data
ββ2ν
Monte Carlo
Background
subtracted
E1 + E2 (keV)
7.37 kg.y
T1/2 = 7.11 ± 0.02 (stat) ± 0.54 (syst) x 1018
y From neutrinos... DK&ER
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Cos(ϑ)
41
Other results from NEMO-3: 2 
NEMO-3
82Se
932 g,
389 days
2750
events
S/B = 4
454 g,
534 days
109 events
S/B = 0.25
NEMO-3
130Te
E1 + E2 (MeV)
9.6 ± 0.3 (stat) ± 1.0 (sys) 1019 y 2.8 ± 0.1 (stat) ± 0.3 (sys) 1019 y 7.6 ± 1.5 (stat) ± 0.8 (sys) 1020 y
48Ca
96Zr
150Nd
925 days
S/B 1.01
9.41g
133 events
S/B 6.76
948 days
7g
E1 + E2 (MeV)
9.11 +0.25-0.22(stat) ± 0.63 (sys) 1018 y 2.3 ± 0.2 (stat) ± 0.3 (sys) 1019 y
42 1019 y
4.4 +0.5-0.4 (stat)± 0.4 (sys)
Xe
TPC
Te02 cryo
calorim.
Germanium
diode cal.
Results for 20 searches
Isotope
Experiment
48Ca
HEP Beijing
Heidelberg-Moscow
IGEX
Irvine
NEMO 2
NEMO 2
LBL
UCI
Osaka
NEMO2
Milano
Caltech/PSI/Neuchatel
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76Ge
82Se
96Zr
100Mo
130Te
136Xe
150Nd
Upper limits
0



(
e
V
)
T
y
r
) m
U
1
/2 (
L
>1.1x1022*
>5.7x1025
>0.8x1025
>2.7x1022
>9.5x1021
>1.3x1021
>2.2x1022*
>2.6x1021
5.5x1022
>5x1021
>1.4x1023
>4.4x1023
>1.2x1021
23-50
2-8
4-14
3-111
2
2-5
2-5
5-6
43
Neutrinoless ββ-decay limits
From Elliot and Vogel, hep-ph/0202264
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Neutrino mass and mass ordering
Inverted
Normal
m32
m22

m12


Degenerate
m22
m12
2
matm
 2.4 105 eV 2

2
 msol

 7.7 105 eV 2
?

2
?  matm
m32
?
0
m(“ e”) < 2.2 eV
Mainz-Troitsk 3H decay
Σm < 0.14 - 1.3 eV
Cosmological models
m(“  ”) < 190 keV
m(“ ”) < 18.2
45 MeV
What is the scale of neutrino masses?
A. Strumia and F. Vissani, ``Neutrino masses and mixings.’’
arXiv:hep-ph/0606054.
F. Feruglio, C. Hagedorn, Y. Lin and L. Merlo,
``Theory of the Neutrino Mass,’’ arXiv:0808.0812 [hep-ph].
0.04
i
m  (0.70+0.02
 ( 0.05)m3e i
-0.04 )m1  (0.300.02 )m2e
*
mββ may be very tiny in case of cancellations due to phases
*
2i
46
HM Claim
NEMO 3
CUORICINO, EXO-200
GERDA(PII)
SuperNEMO
CUORE,EXO
>2020,
1t experiments ( ≥ 2)
>>2020,
>10t experiment
Cosmologically disfavoured region (WMAP)
Projections – ββ0ν
47
Summary
 Direct neutrino mass measurements – sensitivity good
enough only for νe - may be successful in case of
inverted hierarchy
 Search for 0νββ – extremely important because:
It may answer the following basic questions:
 Is the total lepton number conserved? Essential for
understanding the matter-antimatter asymmetry in Universe
 What is nature of neutrinos: Dirac or Majorana
( 0 ββ possible only for Majorana neutrinos)
- essential for understanding the source of particle masses
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