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Absolute neutrino mass determination with the experiment
KATRIN
F. Glück
(on behalf of the KATRIN collaboration)
Johannes Gutenberg-Universität, Mainz
email: [email protected]
Neutrino mass value important for: particle physics, astrophysics, cosmology
Information for neutrino mass:
• neutrino oscillation experiments• direct kinematical measurements• neutrinoless double beta decay• supernovae• cosmological observations (galaxy redshift,
microwave background radiation)
Neutrino oscillation results:
1. At least 2 neutrino masses are finite; lepton mixing matrix has large off-diagonal elements
2. SNO, KAMLAND: m12
2 ≈7·10-5 eV2, θ12 ≈33°
3. SuperKamiokande:2. m23
2 ≈ 2.5·10-3 eV2, θ23 ≈45°3. → mν
(max) ≈ 50 meV
m1 => m2 , m3
No information about absolute mass scale (m1) !
neutrino masses neutrino masses and schemesand schemes
„normal“ mass hierarchy m1<m2<m3
hierarchical
quasi-degenerate
0 decay:
decay kinematics: microcalorimeters MAC-E spectrometers
cosmology &structure formation
astrophysics:SN ToF measurements
Neutrino Mass Measurements Strategies
3H
NEMO3
76Ge @ LNGS ´90-´03(71.7 kg×y)
|mee|=0.44+0.13-0.2 eV
D.N. Spergel et al: m < 0.69 eV (95%CL)S.W. Allen et al: m = 0.56 eV (best fit)
SuperK, SNO, OMNIS + grav.waves: potential for ~1eV sensitivity?
187Re
2
Neutrino mass limit from cosmology:
-free-streaming of neutrinos in universe (because of their small interaction)
-massive neutrinos: gravitational effect, they can reduce the matter density fluctuations
-large neutrino mass → no small scale structure in universe
-neutrino mass limit from cosmology is model dependent (correlations with many other parameters)
m eV m eV
m eV m eVMa ’96
large scales small scales~900 Mpc ~90 Mpc
2dFGRS analysis & -mass limit
160.000 redshifts for 32 point galaxy power spectrum
2 = 32.9
Cosmology: -masses from WMAP & 2dFGRS & Ly
WMAP 220.000 galaxies with <z>=0.11
Combined result :
m < 0.23 eV (95 % CL.)
CMBR
Powerspectrum of CMBR
a challenge for KATRIN ?! How are these results derived, and are they realistic?
astro-ph/0302209
2dFGRS analysis & -mass limit
adding priors for cosmological parameters
Inference of neutrino mass depends on priors for
Hubble parameter h, baryon density b h2, tot,
flat prior on
0.1 <m < 0.5
WMAP results- a critical review
3 main lines of criticism:
- ‚Massive attack‘ on CDM: the role of H0 and the need
for and their influence on (Rowan-Robinson & Sarkar)
- The role of priors and combination of different data
sets (Hannestad, Elgaroy & Lahav)
- Systematic problems of the WMAP result itself
at large and small scales, compatibility with BBN,
the role of the CDM model (PL-CDM or RSI-CDM)
need lab experiments with sub-eV mass sensitivity
Double decaynormal (2) neutrinoless (0)
needed: a) ν(Majorana) b) helicity flip: m()
0 or other new physics
_
Heidelberg Moscow(enriched 76Ge)
Z
E
Evidence for 0 at Heidelberg Moscow Exp.?
„Single-Side-Events“erwartete Position
T1/2
0 = (0.8 -18.3) 1025 y
mee
= (0.11 - 0.56) eV
m(e) = (0.05 - 3.4) eV
(fast) degenerierte?
Nearly same data as earlier (54kgy: 8/1990 - 5/2000),
but now asumptions of peaks in [2000,2080] keV:
background level is lower
fit only [2032,2046] keV with background and peak
peak at 0signal position (2039 keV)
Klapdor-Kleingrothaus et al., MPLA 37 (2001) 2409 (s.also comments: hep-ex/0202018, hep-ph/0205228, hep-ph/0205293)
New, data up to 2003: 72 kgy, with new data selection, new calibration
Klapdor-Kleingrothaus et al., PL B586 (2004) 198
Peak at 2038.1(5) keV (expected: 2039.006(50) keV)Multi-Gauss. Fit: 4.2 significance for 0T
1/20 = (0.34-20.3) 1025 y
mee
= 0.1-0.9 eV (99.7% C.L.)
single side eventsexpected peak position
If 0νββ due to light Majorana neutrino:
τ0ν-1 ~ mee
2 · M0ν2 (1)
mee = Σi Uei2 mi
ν (2)
τ0ν → miν model dependent, because of:
-nuclear matrix element-sign (complex phase) of Uei
2
-possibility for beyond Standard Model mechanism of 0νββ process (supersymmetry, …) → Eq. 1 not valid any more
Possible: present HM signal confirmed, but hierarchical neutrino masses ( mi
ν < 0.2 eV)Test by KATRIN !
phase space determines energy spectrumtransition energy E0 = Ee + E (+ recoil corrections)
experimental observable
– decay kinematics
strong source
(high count rate near E0)
small endpoint energy E0
excellent energy resolution long term stability low bg rate-3 -2 -1 0
Ee-E0 [eV]
1
0.8
0.6
0.4
0.2
0
rel.
rate
[a.u
.]
theoretical spectrum near endpoint
m = 0eV
m = 1eV
dN/dE = K × F(E,Z) × p × Etot × (E0-Ee) × [ (E0-Ee)2 – m2 ]1/2
calorimeters for calorimeters for 187187Re Re decay decayneutrino mass measurement witharray of 10 AgReO4 crystals lower pile up higher statistics
MIBETA experiment(Milano, Como, Trento)
M.Sisti et al, NIM A520(2004)125A.Nucciotti et al, NIM A520(2004)148C. Arnaboldi et al, PRL 91, 16802 (2003)
E0 = 2.46 keV
Top ~ 70-100mK
fit with function
free fit parameters:
endpoint energy
m2
spectrum normal.
pile-up amplitude
background level
calorimeters for calorimeters for 187187Re Re decay decay
Kurie plot of 6.2 ×106 187Re decay events above 700 eV
187187Re Re decay endpoint decay endpoint and mand m
m2 = -112 ± 207 ± 90 eV2
m < 15 eV (90%CL)
future:proposal for a new calorimeter expt. with ~2-3 eV sensitivityforeseen 2007 (?)
E0 = 2465.3 ± 0.5stat ± 1.6syst eV
(8751 h*mg, NIMA520, 2004)
= 2466.1 ± 0.8stat ± 1.5syst eV
(4485 h*mg, PRL91,2003)
fit range: 0.9 to 4 keV
fit function
Flavio Gatti (Genoa):0.5g Re 1—1.7eV sensitivity expectedExpt. Under construction
average neutrino
mass
Need: very high energy resolution & very high luminosity & MAC-E-Filtervery low background
Direct determination of mν by tritium β decay
tritium decay: 3H 3He+ +e-+e _
}
super allowedE
0 = 18.6 keV
t1/2
= 12.3 a
magnetic spectrometers & MAC-E magnetic spectrometers & MAC-E filtersfilters
Principle of the MAC-E-Filter Magnetic Adiabatic Collimation + Electrostatic Filter
(A. Picard et al., Nucl. Instr. Meth. 63 (1992) 345)
● Two supercond. solenoidscompose magneticguiding field
● Electron source (T2)
in left solenoid
● e- in forward direction: magnetically guided
● adiabatic transformation: = E/B = const. parallel e-beam
● Energy analysis byelectrostat. retarding fieldE = EB
min/B
max = EA
s,eff/A
analyse 4.8 eV (Mainz)
principle of an electrostatic filter withprinciple of an electrostatic filter withmagnetic adiabatic collimation (MAC-E)magnetic adiabatic collimation (MAC-E)
adiabatic magnetic guiding of ´s along field lines in stray B-field of s.c. solenoids:Bmax = 6 TBmin = 3×10-4 T
energy analysis bystatic retarding E-fieldwith varying strength:
high pass filter withintegral transmissionfor E>qU
The Mainz Neutrino Mass Experiment 1997-2001
Mainzer-Gruppe
2001:
J. BonnB. Bornschein*L. Bornschein*B. FlattCh. KrausB. Müller**E.W. OttenJ.P.SchallTh. Thümmler**Ch. Weinheimer**
* FZ Karlsruhe** Univ. Bonn
● T2 film at 1.86 K
● quench-condensed on graphite (HOPG)● 45 nm thick (130ML), area 2cm2
● thickness determination by ellipsometry
tilded solenoids
new cryostat
aim: improvement of m by one order of magnitude (2eV 0.2eV ) improvement of uncertainty on m
2 by 100 (4eV2 0.04eV2)
statistics: stronger Tritium source (>>1010 ´s/sec) longer measurement (~100 days ~1000 days)
energy resolution: E/E=Bmin/Bmax spectrometer with E=1eV Ø 10m UHV vessel
From current to future experiments
Mainz: Troitsk:m
2 = -1.2(-0.7) ± 2.2 ± 2.1 eV2 m2 = -2.3 ± 2.5 ± 2.0 eV2
m < 2.2(2.3) eV (95%CL) m < 2.1 eV (95%CL)
C. Weinheimer, Nucl. Phys. B (Proc. Suppl.) 118 (2003) 279 V. Lobashev, private communicationC. Kraus, EPS HEP2003 (neighbour excitations self-consistent) (allowing for a step function near endpoint)
The KArlsruhe TRItium Neutrino Experiment
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
transportmagnets
spectrometersolenoids1010 e-/s
103 e-/s
Pre and main spectrometer
Main spectrometer
● Energy resolution: E = 0.93 eV
● high luminosity:L = A
Seff /4 = A
analyse E/(2E) = 20 cm2
● Ultrahigh vacuum requirements (Background) p < 10-11 mbar
● „simple“ construction: vacuum vessel at HV = electrode + „massless“ screening electrode
● industry study
Pre spectrometer:
● Transmission of electron with highest energy only(10-7 part in last 100 eV) Reduction of scattering probaility in main spectrometer Reduction of background
● only moderate energy resolution required:E = 50 eV
● Test of new ideas (XHV, shape of electrodes, avoid and remove of trapped particles, ...)
KATRIN Main Spectrometer stainless steel vessel (Ø=10m & l=22m) on HV potential minimisation of bg UHV: p ≤ 10-11 mbar
„massless“ inner electrode system
UHV requirements:outgassing < 10-13 mbar l/sinner surface ~ 800m2
volume to pump ~ 1500m3
inner electrodeinstalled in Mainzspectrometer for background tests
intrinsic det. bg 1.6mHz
2.8mHz
Mainz V results
Detector
WGTS source characteristics
pinj = 3.0 × 10-3 mbar ( at T=27K)
qinj = 1.85 mbar l/s = 1020 mol./s = 4.7 Ci/s
(~ 40g T2 per day if no closed loop)
isotopic purity (±2‰)
monitored by Laser Raman spectroscopy
design optimisation ´01 -´03
- tritium purity by tritium laboratory (>95%)
- 2× stronger gaseous source (Ø=75mm Ø=90mm) requires Ø=10m spectrometer)
- optimised measuring point distribution (~5 eV below E0)
- active background reduction by inner electrode system, low background detector (needs further detailed tests)
reference
Statistical uncertainty LoI
5
KATRIN sensitivity & discovery potential
m < 0.2eV (90%CL)
m = 0.35eV (5)
m = 0.3eV (3)
sensitivity
discovery potential
expectation:
after 3 full beam years syst ~ stat
any not accounted variance 2 leads to negative shift of m2:
m2 = -2 2
1. inelastic scatterings of ß´s inside WGTS
- requires dedicated e-gun measurements, unfolding techniques for response fct.
2. fluctuations of WGTS column density (required < 0.1%)
- rear detector, Laser-Raman spectroscopy, T=30K stabilisation, e-gun measurements
3. HV stability of retarding potential on ~3ppm level required
- precision HV divider (PTB), monitor spectrometer beamline
4. WGTS charging due to remaining ions (MC: < 20mV)
- inject low energy meV electrons from rear side, diagnostic tools available
5. final state distribution
- reliable quantum chem. calculations
Systematic uncertainties
a fewcontributions
with each:m
2 0.007 eV2}
Status and schedule of Katrin2001 Presentation of project to community (Bad Liebenzell Workshop)
Foundation of KATRIN collaboration
Letter of Intent (hep-ex/0109033)
First, but significant funds by BMBF, FZ Karlsruhe
2002 Very positive report of International Review Panel
2003 X-Vat Workshop in Bad Liebenzell
Background investigations at Mainz
Setup of pre spectrometer at FZK
2004 Reviewing, proposal and funding
2004 - 2008 Setup of major KATRIN components:
WGTS, transport system, main spectrometer, detector
2008 Commissioning at start of data taking with complete setup
Status of hardware components
Setup of pre-spectrometer at FZ Karlsruhe
s
Electric screening by „massless“ wire electrode
e-
Secondary electrons from wall/electrode
by cosmic rays, environmental radioactivity, ...
wire electrode on slightly more negative potential
U-U U
test installation at Mainz
GitterspannungsabhängigkeitB=5.1T
0
5
10
15
20
25
0 50 100 150 200 250 300
Uscreen [V]
coun
t rat
e [m
Hz]
totalbackground
rate: 2.8mHz
detector background rate 1.6mHz
Mainz V (2004-
PhD thesis: B. Flatt/Mz
New record !April 04
KATRIN pre spectrometer
First realisation: Mainz III
Electric screening by „massless“ wire electrode
Summary
KATRIN:
● A large tritium decay neutrino mass experiment at FZ
Karlsruhe performed by a strong international collaboration
with sub-eV sensitivity (<0.20 eV)
● probes in a unique model independent way:
degenerate and
cosmologically relevant neutrino masses
● complementary to oscillation experiments, 0, cosmology
key experiment w.r.t. neutrino mass scale