Absolute neutrino mass determination with the experiment

KATRIN

F. Glück

(on behalf of the KATRIN collaboration)

Johannes Gutenberg-Universität, Mainz

email: fglueck@uni-mainz.de

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