Transcript DPG Vortrag in Berlin Maerz 2005

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Three
roads to neutrino masses
in der Helmholtz-Gemeinschaft
complementary
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
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Absolute Neutrino Mass Measurements
Beate Bornschein
Lecture I
 Introduction
 Electron neutrino mass measurements - methods
 Status at the begin of the 3rd millennium
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Absolute Neutrino Mass Measurements
Beate Bornschein
Lecture II
 Future of Re experiments – MARE
 Fixing the neutrino mass scale with KATRIN
 Summary & Perspectives
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Absolute
neutrino
masses
--Particle
Data Group
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Absolute neutrino masses – PDG (May 2006)
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Absolute neutrino masses – the ‚traditional‘ way
→ 3He + e- + ne
m(ne) : tritium ß-decay
3H
m(nµ) : pion-decay
p+ →
µ+ + nµ
m(nt) : tau hadr. decay t →
5p + nt
kinematic phase
space studies
m(nm) < 190 keV (PDG2006)
m(nt) < 18.2 MeV (PDG2006)
m(ne) < 2 eV (PDG2006)
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Neutrino oscillations: linking n-masses
n-mass offset?
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Absolute neutrino masses – the ‚traditional‘ way
→ 3He + e- + ne
m(ne) : tritium ß-decay
3H
m(nµ) : pion-decay
p+ →
µ+ + nµ
m(nt) : tau hadr. decay t →
5p + nt
kinematic phase
space studies
m(nm) < 190 keV (PDG2006)
m(nt) < 18.2 MeV (PDG2006)
m(ne) < 2 eV (PDG2006)
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Absolute neutrino masses – the ‚traditional‘ way
→ 3He + e- + ne
m(ne) : tritium ß-decay
3H
m(nµ) : pion-decay
p+ →
µ+ + nµ
m(nt) : tau hadr. decay t →
5p + nt
kinematic phase
space studies
m(nm) < 190 keV (PDG2006)
m(nt) < 18.2 MeV (PDG2006)
m(ne) < 2 eV (PDG2006)
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A short step into the past
 myon neutrino mass
 tau neutrino mass
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Myon neutrino mass
Principle:
E 2  m 2c 4  p 2c 2
Three different quantities needs to be measured with very high precision
Done in three different experiments!
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Myon neutrino mass
1)
Measurement of
mp - , with CPT theorem:
=
mp - mp 
Pionic atom: negative pion is stopped in matter and captured by an atom.
Example:
2)
Measurement of the 4f-3d transition in pionic 24Mg with a crystal
spectrometer
Jeckelmann et al.,
Measurement of
mm 
PhysLettB335 (1994)326
Mohr and Taylor, CODATA,
RevModPhys 77 (2005)
pm 
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Myon neutrino mass
3)
Measurement of
pm 
at Paul-Scherrer Institute (PSI)
Assamagan et al.,
PhyRevD 53 (1996)6065
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Setup at PSI
Assamagan et al.,
PhyRevD 53 (1996)6065
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Different neutrino mass states ni
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Myon neutrino mass
PDG2006
PDG2006
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Tau neutrino mass
Method:
 Hadronic system is composed of 3, 5 or 6 pions
 In tau rest frame energy of hadronic system is fixed:
 mn(t) can computed for given values of mh and Eh*
 mh and Eh* are determined from the measured momenta of the particles
composing the hadronic system
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Tau neutrino mass – ALEPH collaboration
Barate et al.,
Eur. Phys. J. C2 (1998)395
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Tau neutrino mass
PDG2006
(23 entries …)
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Absolute neutrino masses – the ‚traditional‘ way
→ 3He + e- + ne
m(ne) : tritium ß-decay
3H
m(nµ) : pion-decay
p+ →
µ+ + nµ
m(nt) : tau hadr. decay t →
5p + nt
kinematic phase
space studies
m(nm) < 190 keV (PDG2006)
m(nt) < 18.2 MeV (PDG2006)
m(ne) < 2 eV (PDG2006)
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Electron neutrino mass - again a look into PDG2006
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Neutrino mass from SN1987A
Time of flight measurement:
E 2  m 2c 4  p 2c 2
SN1987A
L  1.5 ∙ 1018 km
 1.6 ∙ 105 light years
One neutrino with m, E (m2 << E2)
t  t E - t SN
L  m 2c 4 
  1 
2 
c 
2E 
Two neutrinos with m, E1, E2
L m 2c 4  1
1 
t E 1 - t E 2  ( t SN 1 - t SN 2 )  
- 2

2
c
2  E1 E2 
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Neutrino mass from SN1987A
Time of flight measurement:
E 2  m 2c 4  p 2c 2
One neutrino with m, E
t  t E - t SN
L  m 2c 4 
  1 
2 
c 
2E 
Two neutrinos with m, E1, E2
L m 2c 4  1
1 
t E 1 - t E 2  ( t SN 1 - t SN 2 )  
- 2

2
c
2  E1 E2 
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Dependent on
SN model !
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Neutrino mass from SN1987A: results
PDG2006
T.J. Loredo et al., PRD65 (2002) 063002, 39 pp
 improved SN model
 improved data modeling
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Neutrino mass from SN20xx ???
Actually no competition with -decay experiments:
 not sensitive to sub-eV neutrino masses (uncertainty in emission time at SN)
 galactic SN only expected every 40 years
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β-decay and neutrino mass
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ß-decay and neutrino mass
kinematic measurement of
electron neutrino mass m(ne):
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ß-decay and neutrino mass
kinematic measurement of
electron neutrino mass m(ne):
n e  0.85n 1  0.51n 2
n m  -0.36n 1  0.60n 2  0.71n 3
n t  0.36n 1 - 0.60n 2  0.71n 3
scaling in ß-decay: experimental
observable is mn2
n-mass eigenstates mi too close to be resolved experimentally with
E ~ 1 eV for single electrons at ß-decay endpoint
- ß-decay & n-oscillation experiments allow to fully reconstruct
mass eigenstates mj as n-oscillations provide Uei and Δm2ij
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ß-decay and neutrino mass
kinematic measurement of
electron neutrino mass m(ne):
ß-source requirements :
 high ß-decay rate
 low ß-endpoint energy E0
 no strongly forbidden transition
 …, see further discussion,
dependent on experiment
ß-detection requirements :
 - high resolution (E< few eV)

- large solid angle (W ~ 2p)

- low background
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E0 = 18.57 keV
T1/2 = 12.3 y
superallowed
E0 = 2.47 keV
T1/2 = 43.2 Gy
unique 1st forbidden
3H
187Re
calorimeter:
source = detector
spectrometer:
source ≠ detector
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Electron analyzer
Source
Electron counter
Based on
Andrea Giuliani,
MARE collaboration
T2
high activity
high energy resolution
 integral spectrum: select Ee > Eth
spectrometers
microcalorimeters
n
electron
MAINZ-TROITSK  KATRIN
MIBETA, MANU  MARE
bolometer

 high efficiency
 low background
excitation
energies
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high energy resolution
 differential spectrum: dN/dE
When in presence of decays to
excited states, the calorimeter
measures both the electron and
the de-excitation energy
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Tritium β-decay experiment
3H

3He+
+ e- + ne
with
E0=18.6 keV
count rate [a.u.]
1.2
1.0
0.8
0.6
mn = 0
0.4
10
0.2
0
-13
mn> 0
0
5 10 15 20
energy E [keV]
-3
-2
-1
E - E0 [eV]
0
Measurement of T2 β-decay spectrum in the region around the endpoint E0
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Why tritium?
recoil energy and excitation neglected
2
N ( E )  const  M F ( Z , E ) p( E  me c 2 )( E0 - E ) ( E0 - E ) 2 - mn2 c 4
nuclear matrix
element
Fermi
function
Tritium: E0 = 18.6 keV,
TH = 12.3 a
 Superallowed transition:  matrix element M is not energy dependent
 Low endpoint energy:
 relative decay fraction at the endpoint is
comparatively high
 Short half life:
 specific activity is high
 low amount of source material
 low fraction of inelastic scattered electrons
 Hydrogen isotope:
 simple atomic shell
 final states precisely calculable
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Tritium β-decay experiment: basic requirements
 very high energy resolution
10
 very high luminosity
N [a.u.]
8
L = ASeff W/4p
6
m n = 0 eV
4
- large source area
2 * 10 -13
2
- large accepted solid angle
m n = 1 eV
0
-3
-2.5
-2
 high -decay rate
-0.5
-1.5 -1
E - E0 [eV]
0
0.5
 very low background
Best solution: tritium source combined with MAC-E filter
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Principle of an electrostatic filter with
magnetic adiabatic collimation (MAC-E)
MAC-E Filter:
 adiabatic guiding of  particles
along the magnetic field lines
 large accepted solid angle
W  2p
 inhomogen B-Field:
adiabatic transformation
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Principle of an electrostatic filter with
magnetic adiabatic collimation (MAC-E)
MAC-E Filter:
 adiabatic guiding of  particles
along the magnetic field lines
 large accepted solid angle
W  2p
 inhomogen B-Field:
adiabatic transformation
 electrostatic retarding field:
high pass filter !
 E = Bmin/Bmax E0
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Principle of an electrostatic filter with
magnetic adiabatic collimation (MAC-E)
MAC-E Filter:
0.4
transmission function
0° guiding of  particles
45°

0.35adiabatic
 E = 4.8 eV
0.3along the magnetic field lines
0.25
0.2large accepted solid angle
0.15
W  2p
0.1
0.05

inhomogen B-Field:
0
-2
0
2
4
adiabatic
transformation
6
E - qU [eV]
 electrostatic retarding field:
high pass filter !
 E = Bmin/Bmax E0
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Principle of a MAC-E filter II
MAC-E Filter - method
--eU
eU00
rejected
accepted
amplitude
 Scanning β spectrum and
background region by varying
spectrometer voltage U0
EE00
 All β electrons with an energy
higher than the filter energy –eU0
accepted and counted
energy
spectrum region
bg region
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 Measuring time per data point
is experiment specific
Typical values:
20 to 60 s per voltage set
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Principle set-up of a tritium -decay experiment
Tritium
Source
1) Very high
source strength
2) Very good
understanding
of systematic
effects
(Magnetic)
Transport
System
1) No disturbance of
kinetic energy of
beta decay electrons
(adiabatic transport)
Spectrometer
(Energy Filter)
Detector
1) Very high
energy resolution
1) Very low
background
2) Very low
background
2) Segmented
2) No loss of electrons
3) Elimination of residual
tritium molecules
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The Mainz neutrino mass experiment (1997-2001)
Detector
Molecular T2 source
Spectrometer
 T2 film at 1.9 K
 23 ring electrodes
 Quench condensed
on graphite (HOPG)
 4.8 eV resolution
 L = 4 m, Ø = 1 m
 d  480Å (140 ML)
A = 2 cm2
 20 mCi activity
 Vacuum better
10-10 mbar
QCTS = Quench Condensed
Tritium Source
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 5 segments
 silicon
LHe cooled shield
laser for ellipsometry
continuous flow
cryostat: 1.9K
e-
graphite tritium
substrate film
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The Mainz neutrino mass experiment (1997-2001)
KATRIN
2006
Mainz neutrino
group 2001:
J. Bonn
B. Bornschein*
L. Bornschein*
B. Flatt
Ch. Kraus
B. Müller **
E.W. Otten
J.P. Schall
Th. Thümmler**
Ch. Weinheimer**
*  FZ K + U Karlsruhe
**  U Münster
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Source systematics
laser for ellipsometry
LHe cooled shield
e-
continuous flow
cryostat: 1.9K
graphite tritium
substrate film
Quench Condensed Tritium Source
QCTS, before 1997:
Investigation of source
effect in Mainz:
Source temperature 4.2K, 2.8 K
 Roughening transition !
 Increased energy loss
Entering the solid state
physics…
time
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Stray light measurements
1.6 K
condensation
4.2 K
dewetting
dewetting
1200
>5K
desorption
state of equilibrium
intensity [a.u.]
1100
1000
900
desorption
800
quench
condensed
film
700
0
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1000
2000
3000
time [s]
4000
5000
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Results of stray light measurements
1400
Model of surface diffusion
Δt ≈ Δt0  exp(Δ W / kT)
1200
stray light [a.u.]
Fleischmann et al.
Eur. Phys. J. B 16 (2000) 521
T = 1.6 K
condensation
(Arrhenius-law)
Δt = characteristic dewetting time
T = 4.0 K
T = 4.4 K
T = 3.8 K
1000
Δt
T>5 K
desorption
800
600
400
0
ΔW = activation energy
1000
2000
time [s]
3000
4000
 Dewetting time Δt (T=1.9 K) > 1.2 a (95% C. L.)
 long term measurements are possible with quench condensed
tritium films if T< 1.9 K
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Source systematics & negative mass squares
lower limit of fit
laser for ellipsometry
LHe cooled shield
fit
e-
continuous flow
cryostat: 1.9K
graphite tritium
substrate film
run91
run98, Q5
100
50
m
Source temperature 4.2K, 2.8 K
 Roughening transition !
 Increased energy loss
2
2
4
[eV /c ]
Quench Condensed Tritium Source
QCTS, before 1997:
150
0
-50
-100
time
-150
18.3
18.4
18.5
18.6
E low
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Underestimated energy loss –
the most often reason for negative mass squares
spectrum with additional
energy loss
undisturbed spectrum
E0
E0 of fit
-3
-2
-1
E - E0 [eV]
0
If we have underestimated or just missed some energy loss mechanism,
then the fit finds a too low endpoint which shifts the squared neutrino mass
towards negative values (count rate “above” the endpoint)
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Results of neutrino mass measurements of last 2 decades
mn2c4 [eV2]
100
 Long series of tritium
-decay experiments
50
0
-50
Livermoore
Los Alamos
-100
 “Problem of negative mass
squares” disappeared due
to better understanding of
systematic effects
Mainz
Tokyo
-150
 Troitsk:
Troitsk
Troitsk (step)
-200
Zürich
-250
electrostatic spectrometers
(MAC-E Filters)
-300
-350
1988
1990
1992
 Mainz:
Quench condensed tritium
source (QCTS)
magnetic spectrometers
1986
Gaseous tritium source
(WGTS)
1994
1996
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1998 2000
year
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QCTS - investigations of systematic effects
 Roughening transition of T2 film
 Inelastic scattering
etime
Determination of dynamics: ΔE = (45±6) kBK
no roughening transition below 2 K
L. Fleischmann et al., J. Low Temp. Phys. 119 (2000) 615,
L. Fleischmann et al., Eur. Phys. J. B16 (2000) 521
 Self-charging of T2 film
Determination of cross section:
σtot = (2.98±0.16) 10-18 cm2
Det. of energy loss function
V.N. Aseev et al., Eur. Phys.J. D10 (2000) 39
 Long time behavior of T2 film
-
2 V, d = 350 A
time
H2: +0.1 nm/d
T2: -0.06 nm/d
Determination of critical field: Ecrit = (63±4) MV/m
=> slight broadening of energy resolution
Rest gas condensation & evaporation
=>Effect limits measurement time
H. Barth et al., Prog. Part. Nucl. Phys. 40 (1998) 353
B. Bornschein et al., J. Low Temp. Phys. 131 (2003) 69
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
Beate Bornschein, Tritium Laboratory Karlsruhe # 47
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45
Self-charging of QCTS
data
fit
40
e
 First hint:
shift of the β-endpoint
energy (1997)
counts [1/s]
35
30
25
20
15
Kr-83 submonolayer
on 240 ML deuterium
10
17.81
 Idea:
Charging of the tritium
film (40 mCi ≈ 1.5E9 electrons/s)
17.815
17.82
17.825
17.83
17.835
17.84
17.845
4800
4600
data
fit
4400
e

counts [1/s]
Measurement with
Kr-83m conversion
electrons
4200
4000
shift e * U
3800
3600
dE
3400
U
Kr-83 submonolayer
on 120 ML tritium
3200
3000
17.81
17.815
17.82
17.825
17.83
17.835
17.84
17.845
energy [keV]
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
Beate Bornschein, Tritium Laboratory Karlsruhe # 48
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Time dependency
of charging
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
+ +

Assumption:
tritium β-decay
&
existence of critical field
E
d0
d0

----
d0
+
+ +
+
+ +
d1

---61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
d0
d
d
d
tcrit
d1
d0
d
EC
E
d0
d
EC
E
+ + +
+ + +
-- d
-- 1
--
d0
d
E
+ + +
+ + +
---
+
equal distribution
of charges
d
d1
d0
d
EC
+
+
+
E
+
+
+ d
d0
d0
d
capacitor
EC
Beate Bornschein, Tritium Laboratory Karlsruhe # 49
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Result of measurement
Steady state is characterized
by a practically constant,
critical electric field strength
Ecrit ≈ 62 MV/m
≈ 20mV/monolayer
over the film, at which the
residual positive charges
attain sufficient mobility to
penetrate the film towards
the conducting substrate.
0
-1
test films
energy shift [eV]
-2
Q5
-3
Q8
-4
-5
E c = 62.6  4.0 MV/m
-6
Q2
-7
0
200
400
600
800
film thickness [ Å ]
B. Bornschein et al., J. Low Temp. Phys. 131 (2003) 69
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
1000
β-spectroscopy:
Limits either resolution (in
case of thick films) or count
rate (in case of thin films).
Reason for using gaseous
source in KATRIN experiment!
Beate Bornschein, Tritium Laboratory Karlsruhe # 50
Forschungszentrum Karlsruhe
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Results of Mainz experiment (1998/1999 + 2001)
10
150
run91
run98, Q5
5
m2n [eV2/c4]
50
2
2
4
[eV /c ]
100
m
1998/1999 data
2001 data
0
-50
0
-5
-100
-150
18.3
18.4
18.5
18.6
-10
E low
18.3
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
18.4
18.5
lower limit of fit interval Elow
18.6
[keV]
Beate Bornschein, Tritium Laboratory Karlsruhe # 51
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Results of Mainz experiment
Data of 20 weeks run time
added for evaluation
With neighbour excitation from
calculation
(Kolos et al., Phys. Rev. A37 (1988) 2297)
m2(n) = -1.2 ± 2.2 ± 2.1 eV2

m(n) < 2.2 eV (95% C.L.)
Ch. Weinheimer, Nucl. Phys. B
(Proc. Suppl.) 118 (2003) 279,
C. Kraus et al., Nucl. Phys. B
(Proc. Suppl.) 118 (2003) 482
Neighbour excitation fitted from
own data
PDG2006
m2(n) = -0.6 ± 2.2 ± 2.1 eV2

m(n)< 2.3 eV (95% C.L.)
C. Kraus et al., Eur. Phys. J. C40 (2005) 447
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
Beate Bornschein, Tritium Laboratory Karlsruhe # 52
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Troitsk neutrino mass experiment
= Windowless Gaseous Tritium Source & MAC-E Filter
Principle of WGTS:
5T
0.8T
28K
5T
-
to
spectrometer
e
tritium gas
injection
Dominant systematic uncertainty:
Energy loss due to inelastic scattering of decay electrons
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
Beate Bornschein, Tritium Laboratory Karlsruhe # 53
Forschungszentrum Karlsruhe
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HVT-TLK
T2 purification
Troitsk setup
Ti pump
Hg pump
MAC-E-Filter
8T
e-gun
5T
0.8 T
0.5-1 mT
2.6 T
5T
Detector
Windowless Gaseous
Tritium Source
Magnetic Transport System
+ Differential Pumping Section
0
1m
WGTS
Spectrometer
Detector
 26-28 K
 3 ring lectrodes
 Si(Li)
 L=3 m, Ø= 5 cm
 T2:HT:H2 = 6:8:2
 column density: 1017cm-2
 3.5 eV resolution
 L=6 m, Ø=1.2 m
 P = 10-9 mbar
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
2m
Beate Bornschein, Tritium Laboratory Karlsruhe # 54
Forschungszentrum Karlsruhe
in der Helmholtz-Gemeinschaft
HVT-TLK
T2 purification
Troitsk setup
Ti pump
Hg pump
MAC-E-Filter
8T
e-gun
5T
0.8 T
0.5-1 mT
2.6 T
5T
Detector
Windowless Gaseous
Tritium Source
Magnetic Transport System
+ Differential Pumping Section
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
0
1m
2m
Beate Bornschein, Tritium Laboratory Karlsruhe # 55
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Troitsk Anomaly
dE
U
step position below E 0 [eV]
E0
month in the year
 Observation of an excess count rate (‘step’) close to the endpoint
(equivalent to a mono energetic line in original β-spectrum)
 Location: 5 – 15 eV below E0, intensity: ≈ 10-10 of total T2-decay rate
 Periodicity = 0.5 years ?
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
Beate Bornschein, Tritium Laboratory Karlsruhe # 56
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Troitsk Results
 Strong correlation between step parameters (anomaly) and mn2
 Requires description of anomaly phenomenologically by
adding 2 additional fit parameters (standard: E0, m2, Amp, Bg):
step_position, step_amplitude
1994-98 results (6 parameter fit):
mn2 = -1.9 ± 3.4 ± 2.2 eV2/c4
PDG2006
=> mn < 2.5 eV/c2 (95% C.L.)
V. Lobashev et al., Phys. Lett. B 460 (1999) 227
1994-99/01 results (6 parameter fit):
mn2 = -2.3 ± 2.5 ± 2.0 eV2/c4
=> mn < 2.2 eV/c2 (95% C.L.)
V. Lobashev, Proceedings 17th International Conference on Nuclear Physics in
Astrophysics, Debrecen/Hungary, 2002, Nucl. Phys. A 719 (2003) 153
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
Beate Bornschein, Tritium Laboratory Karlsruhe # 57
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Coincident measurements in Troitsk and Mainz
Mainz results:
 No significant
change of 2
 => no indication
of an anomaly
 Troitsk anomaly
is very likely an
experimental
artefact which is
not present in
Mainz
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
Beate Bornschein, Tritium Laboratory Karlsruhe # 58
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61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
PDG2006
Beate Bornschein, Tritium Laboratory Karlsruhe # 59
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Electron neutrino mass
PDG2006
^
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
Beate Bornschein, Tritium Laboratory Karlsruhe # 60
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Absolute Neutrino Mass Measurements
Beate Bornschein
Lecture II
 Future of Re experiments – MARE
 Fixing the neutrino mass scale with KATRIN
 Summary & Perspectives
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
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Additional transparencies
61st Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
Beate Bornschein, Tritium Laboratory Karlsruhe # 62
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Model for charging
 electrons are
leaving the T2 film
400
 pos. Ions are
remaining
in the film
 mobility of charges:
proportional to
200
W [ kB K]
 need charge
compensating
current from/to
substrate
300
100
+
0
-100
e * Ecrit * g
exp (-W/kT)
 T < 2 K  no mobility!
-200
 Charging
-300
 additional el. Field
g
n-1
 movement of charges at
E
61st
Scottish University Summer School in Physics: Absolute Neutrino Mass Measurements
crit
n
monolayer
n+1
Beate Bornschein, Tritium Laboratory Karlsruhe # 63