Direct Measurements of the Neutrino MassKlaus EitelForschungszentrum KarlsruheInstitute for Nuclear Physicsklaus.eitel@ik.fzk.de

neutrino masses in particle physics & cosmology (mass scenarios, ns as HDM) micro-calorimeters (Mibeta: 187Re in AgReO4) electrostatic spectrometers (Mainz, Troitsk, KATRIN)Direct Measurements of the Neutrino Mass

neutrino masses and schemesnormal mass hierarchy m1

neutrino masses and cosmologysecond task:decide whether n contributeas Hot Dark Matter

1087 ns per flavor from BB!(without n annihilation; astro-ph/0404585)r [% of rcr]

0nbb decay:

b decay kinematics: microcalorimeters MAC-E spectrometerscosmology &structure formation

astrophysics:SN ToF measurementsNeutrino Mass Measurements Strategies3HNEMO376Ge @ LNGS 90-03(71.7 kgy)|mee|=0.44+0.13-0.2 eVD.N. Spergel et al:Smn < 0.69 eV (95%CL)S.W. Allen et al:Smn = 0.56 eV (best fit)SuperK, SNO, OMNIS + grav.waves: potential for ~1eV sensitivity?187Re2nbb

phase space determines energy spectrumtransition energy E0 = Ee + En (+ recoil corrections)experimental observableb 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

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0rel. rate [a.u.]theoretical b spectrum near endpointmn = 0eVmn = 1eVdN/dE = K F(E,Z) p Etot (E0-Ee) [ (E0-Ee)2 mn2 ]1/2

b decay kinematics and 0nbb decayb-decay kinematics0nbb decay direct n mass determination only possible for Majorana ns

if n masses are not resolvedaverage neutrino masscoherent sum of mass EVs

m2(ne) = S |Uei2| m(ni)2mee(n) = | S |Uei|2 eia(i)m(ni) |

incoherent sum, real average, partial cancellation possible since 0 |Uei2| 1(not fully since SNO says: no max. solar mixing)

m2(ne) vs. mee(n): complementary information, differences due to Dirac neutrinoCP-phasesProblems with nuclear matrix elementsOther processes (right-handed currents, Susy-particles, ...)

m calorimeters for 187Re b 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)

MANU2 experiment (Genoa) F. Gatti, Nucl. Phys. B (Proc.Suppl.) 91 (2001) 293)

E0 = 2.46 keVTop ~ 70-100mK

fit with function

free fit parameters:

b endpoint energy mn2 b spectrum normal. pile-up amplitude background levelm calorimeters for 187Re b decayKurie plot of 6.2 106 187Re b decay events above 700 eV Mibeta

187Re b decay endpoint and mnmn2 = -112 207 90 eV2

mn < 15 eV (90%CL) future:proposal for a new calorimeter expt. with ~2-3 eV sensitivityforeseen 2007 (?)F. Gatti (n04): 0.5g Re 11.7 eV sensitivity expectedE0 = 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

principle of an electrostatic filter withmagnetic adiabatic collimation (MAC-E)

principle of an electrostatic filter withmagnetic adiabatic collimation (MAC-E)adiabatic magnetic guiding of bs along field lines in stray B-field of s.c. solenoids:Bmax = 6 TBmin = 310-4 T

energy analysis bystatic retarding E-fieldwith varying strength:

high pass filter withintegral b transmissionfor E>qU

magnetic spectrometers & MAC-E filters

latest results from the MAINZ experimentfree fit for anex, mn2 for last 170eVfrozen T2 on HOP graphiteT=1.86K A=2cm2, d~130ML (~45nm)20mCi activityspectr.: l=2m, =0.9mDE=4.8eV1994-2001 improvements in systematics: roughening of T2 film inelastic scattering self charging of T2 filmcondensed T2 film neighbour excitationsW.Kolos et al., PRA37(1988): anex=5.9%; e=14.6eV

Mainz 1998-2001: anex=(51.62.2)% with e=16.1eVC. Kraus, Eur.Phys.J. C33, s01 (2004), n04

aim:improvement of mn by one order of magnitude (2eV 0.2eV ) improvement of uncertainty on mn2 by 100 (4eV2 0.04eV2)

statistics:stronger Tritium source (>>1010 bs/sec) longer measurement (~100 days ~1000 days)

energy resolution: DE/E=Bmin/Bmax spectrometer with DE=1eV 10m UHV vesselFrom current to future experimentsMainz:Troitsk:mn2 = -1.2(-0.7) 2.2 2.1 eV2mn2 = -2.3 2.5 2.0 eV2mn < 2.2(2.3) eV (95%CL) mn < 2.05 eV (95%CL)

C. Weinheimer, Nucl. Phys. B (Proc. Suppl.) 118 (2003) 279V. Lobashev, Nucl.Phys. A719 (2003) 153cC. Kraus, Eur.Phys.J. C33 (neighbour excits self-consistent)(allowing for a step function near endpoint)

The KArlsruhe TRItium Neutrino ExperimentForschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft

KATRIN~70 m beamline, 40 s.c. solenoidsKATRIN location at FZKarlsruhe

Windowless Gaseous Tritium Sourceat Tritium Laboratory Karlsruhesingle WGTS solenoid (l=1m)WGTS parameters:total length l = 10m, inner diam. = 90mm, Bsource = 3.6T, isotopic purity > 95% T2 T = (27 0.03)K(l=10m)

WGTS source characteristicspinj = 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

electrostatic spectrometerstandem designelectrostatic pre-filtering & analysis of tritium -decay electrons~1010 bs/sec ~103 bs/sec ~10 bs/sec (qU=E0-25eV)pre-spectrometer main spectrometerfixed retarding potential 18.45kVvariable retarding potential 18.5 18.6 kV = 1.7m; length = 3.5m = 10m; length = 24mDE 60 eVDE = 0.93 eV (18.575keV) detailed el.-magn. design!

KATRIN Main Spectrometer stainless steel vessel (=10m & l=24m) on HV potential minimisation of bg UHV: p 10-11 mbar massless inner electrode systemUHV requirements:outgassing < 10-13 mbar l/sinner surface ~ 800m2volume to pump ~ 1500m3inner electrodeinstalled in Mainzspectrometer for background testsintrinsic det. bg 1.6mHz2.8mHzMainz V results

Detector conceptsegmented PIN-diode 44 x 44 mm64 segments 5x5 mm,bonded onto ceramicswith FET stage8x8 Pin-Diode fromCanberra SemiConductorsthe prespectrometer detector: prototype of KATRIN main detector64 channel FET stage backside of UHV flange,with board for 64 preamps PIN diode arrayT-structure multipixel PIN diode

KATRIN sensitivity & discovery potentialdesign optimisation 01 03statistical accuracy on mn2LoI 9/2001

2 stronger gaseous source (=75mm =90mm) required =10m spectrometer) isotopic T purity 70% 95%design optimisation 01 03statistical accuracy on mn2LoI 9/2001LoI 9/2001KATRIN sensitivity & discovery potential

2 stronger gaseous source (=75mm =90mm) required =10m spectrometer)

optimised measuring point distribution (~5 eV below E0)design optimisation 01 03statistical accuracy on mn2LoI 9/2001referenceKATRIN sensitivity & discovery potential

2 stronger gaseous source (=75mm =90mm) required =10m spectrometer)

optimised measuring point distribution (~5 eV below E0)

active background reduction by inner electrode system, low background detector (needs further detailed tests) LoI 9/2001referencedesign optimisation 01 03statistical accuracy on mn2KATRIN sensitivity & discovery potential

KATRIN - systematic uncertainties1. inelastic scatterings of s inside WGTS requires dedicated e-gun measurements, unfolding techniques for response fct. 2. HV stability of retarding potential required: ~ppm level precision HV divider (PTB), monitor spectrometer beamline 3. fluctuations of WGTS column density required < 0.1% stability rear detector, Laser-Raman spectroscopy, T=30K stabilisation, e-gun measurements 4. WGTS charging due to remaining ions (MC: f

5sKATRIN sensitivity & discovery potentialmn < 0.2eV (90%CL)mn = 0.35eV (5s)

mn = 0.3eV (3s)sensitivitydiscovery potentialexpectation:

after 3 full beam years ssyst ~ sstat

status of hardware activitiespre-spectrometer differential pumping sectionWGTS pre-specdetectorassembly

conclusions & outlook absolute neutrino mass of prime importance

microcalorimeter (MIBETA 187Re): mn