[PPT] - Direct neutrino mass measurement 16 th International Conference on PowerPoint Presentation

SLIDE 1

KIT – The Research University in the Helmholtz Association

Guido Drexlin, Institute of Experimental Particle Physics ETP, Department of Physics

www.kit.edu

Direct neutrino mass measurement

introduction
electron capture on holmium
beta-decay of tritium
first n-mass result of KATRIN
keV-sterile neutrinos
conclusion

16th International Conference on Topics in Astroparticle Physics and Underground Physics (TAUP) Toyama, September 9-13, 2019

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KIT-KCETA 2

Sept. 13, 2019

assessing neutrino masses: the three-fold way

2 3 1 2

) (

i i ei e

m U m





  n

kinematics weak decays

n

ß-decay: 3H
EC: 163Ho
model-

independent:

conservation of E,p

LSS: CMB,

GRS, lensing

model-

dependent: LCDM





3 1 i i tot

m m





 

3 1 2 i i ei ßß

m U m

ßß-decay:

76Ge,130Te,136Xe

model-

dependent: Majorana-n

G. Drexlin – direct neutrino mass measurement

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Sept. 13, 2019

n-masses from kinematic studies – the challenge

normal hierarchy  setting the stage: experimental observables m(ne) in ß-decay & EC mßß in 0nßß-searches (Majorana/CP-phases)

from: C. Weinheimer, arXiv:0912.1619

0.01 0.1 1 0.01 0.1 1

inverted hierarchy Sm(ni) (eV) Sm(ni) (eV)

1 0.1 0.01

tritium ß-decay

experimental observable (eV)

tritium ß-decay

uncertainties in phases (0nßß)

n3 n1 n2 Dm2

atm

m2 Dm2

sol

ne nµ nt Dm2

atm

m2 Dm2

sol

n2 n1 n3

G. Drexlin – direct neutrino mass measurement

~ 10 meV ~ 50 meV

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Sept. 13, 2019

1950 1960 1970 1980 1990 2000 2010 2020

calendar year neutrino mass limit (meV)

106 105 104 103 102 101

Moore´s law* of direct n-mass sensitivities

G. Drexlin – direct neutrino mass measurement

MAC-E- filters: Mainz, Troitsk m(ne) < 2 eV (95% CL)  setting the stage: experimental progress over past decades due to new technologies gaseous molecular tritium source: Los Alamos

*courtesy of JF Wilkerson

quasi-degenerate masses

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Sept. 13, 2019

EC ON HOLMIUM-163: ECHo, HOLMES

G. Drexlin – direct neutrino mass measurement

m(ne) < 225 eV (1987)

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Sept. 13, 2019

electron capture: Q-value

 EC-process of 163Ho : 163Ho + e- → ne + 163Dy* (t1/2 = 4570 yr)

M-shell

163

EC

e-

ne QEC  no EC from K, L shells possible

A. De Rújula, M. Lusignoli, Phys. Lett 118B (1982)
G. Drexlin – direct neutrino mass measurement

 – after EC: ne carries away energy & momentum

QEC: Penning trap mass spectroscopy M(163Ho) – M(163Dy) QEC = (2833 ± 30stat ± 15syst) eV

agrees with MMC-value from Ho-spectrum

QEC = (2858 ± 10stat ± 50syst) eV

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Sept. 13, 2019

0 0.5 1 1.5 2 2.5

electron capture: de-excitation

 EC-process of 163Ho : 163Ho + e- → ne + 163Dy* (only from s½ or p½ orbitals)

 – atomic hole state de-excites to atomic g.s.  Auger & Koster-Kronig electrons, X-rays

X-ray

electrons M

e-

hole

TC: calorimetric energy from atomic de-excitations

163

TC (keV) full de-excitation spectrum

M1 M2 N1

1/l dl/dEC (keV-1)

N2 O 102 10 1 10-1 10-2 10-3 finite hole t: Breit-Wigner resonance (Gi)

G. Drexlin – direct neutrino mass measurement

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0 0.5 1 1.5 2

electron capture: n-mass

TC (keV) full de-excitation spectrum

M1 M2 N1

1/l dl/dEC (keV-1)

N2 O 102 10 1 10-1 10-2 10-3 finite hole t: Breit-Wigner resonance (Gi)

1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0

TC – QEC (eV)

10-12 ∙1/l dl/dEC (eV-1)

14 12 10 8 6 4 2

spectrum close to QEC

m(ne) = 0 eV m(ne) = 0.5 eV

4 / ) ( 1 2 ) ( ) ( ) ( ~ d d

2 2 2 2 2 i i C i i i i i i e C EC C EC C EC

E T B C n m T Q T Q T G    G         



  n l M1, M2,…

G. Drexlin – direct neutrino mass measurement

 shape:

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calorimeters to measure 163Dy* atomic de-excitation

 MMC: metallic magnetic calorimeters with paramagnetic sensor Au:Er dT in absorber from EC-decay  change in magnetism dM of param. sensor signal:

E C T M T T M

tot S

d d     D     1 ~ ~

M

thermal link SQUID

G. Drexlin – direct neutrino mass measurement

 thermal micro-calorimeters with TES read-out

thermal link absorber

ne

TES

V

C V E T   D d

calorimeter signal:

DR s.c. n.c. DT

TES SQUID

dT in absorber from EC-decay  change in temperature dT of TES thermistor

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calorimeters to measure 163Dy* atomic de-excitation

 ECHo Collaboration: 8 institutions ~ 50 scientists

G. Drexlin – direct neutrino mass measurement
ECHo 1-k detector array (working horse)

64 pixels implanted at RISIKO (Uni Mainz)

activity per pixel: Apix ~ 1 Bq (Atot ~ 50 Bq)

10 mm  HOLMES Collaboration: 6 institutions ~ 40 scientists ECHo 1-k chip

first pixels now being

characterized: DE = 4.5 eV@ 2.6 keV Dt ~ 2.8 µs

ion implanter being

being tested (Genova)

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1 2 3 4 5 energy (keV) counts / 0.1 eV

EC on holmium – challenges

1014 1012 1010 108 106 104 102 100 fpu = 10-6

163Ho-EC

+ fpu

G. Drexlin – direct neutrino mass measurement

 challenges in reaching a sub-eV sensitivity

good statistics in endpoint region:

Nev > 1014 → overall A ~ 1 MBq

limit unresolved pile-up (fpu ~ a · tr)

fpu < 10-6 for tr < 1 µs  limit pixel a ~ 10 Bq

very good energy resolution at endpoint

DE(FWHM) < 3 eV

detailed understanding of spectral features:

2-hole excitations, line broadening

very low background level

Rbg < 10-5 events/eV/pixel/day

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ECHo – final LSM result

 final results from a first MMC-measurement phase at Modane (LSM) m(ne) < 150 eV (95% C.L.) QEC = (2838 ± 14) eV

G. Drexlin – direct neutrino mass measurement
4 pixels over 4 days (275 000 counts)

Apix = 0.2 Bq DEFWHM = 9.2 eV

profile log-likelihood ratio test:

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from ECHo-1k to ECHo-100k

 ECHo-1k: 2015 - 2020

demonstrate scalability of arrays 
MMC: DEFWHM < 5 eV
total activitiy A ~ 100 Bq
1 y measurement phase:

 limit m(ne) < 10 eV (90% CL)  ECHo-100k: 2020 ff

ECHo-100k chip in fabrication
12000 pixels (Apix ~ 10 Bq)
microwave SQUID multiplexing
3 y measurement phase

 limit m(ne) < 1.5 eV (90% CL)

G. Drexlin – direct neutrino mass measurement

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ß-DECAY OF TRITIUM: PROJECT8, KATRIN

m(ne) < 2 eV

G. Drexlin – direct neutrino mass measurement
M. Tanabashi et al. (PDG), PRD 98 (2018) 030001

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tritium ß-decay: kinematics

electron energy (keV)

5 10 15 count rate (arb. units) 6 4 2

) ( ) , ( ) ( ) ( ) ( d d

2 2 i i e i

m E E Z E F m E E E E m E p C E              G 

 continuous ß-spectrum described by Fermi´s Golden Rule, measurement of effective mass m(ne) based on kinematic parameters & energy conservation

2 3 1 2

) (

i i ei e

m U m





  n

G. Drexlin – direct neutrino mass measurement

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ß-spectroscopy: molecular & atomic tritium

atomic source (T) sensitivity limit ~ 40 meV (?) T2

3HeT+

e- ne

_

ne e- ro-vib

G. Drexlin – direct neutrino mass measurement

excitation energy (eV) probability electronic ground state ro-vib excitations calculated final state distribution of T2 0 2 4 20 30 40 50 0.05 0.04 0.03 0.02 0.01 0.00 molecular source (T2) – sensitivity limit ~ 100 meV FSD excited electronic states

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B. Monreal, J. Formaggio, Phys. Rev. D 80, 051301(R) (2009)

f0 = w0 / 2 ≈ 27 GHz B = 1 T Ee,kin = 18.57 keV  Cyclotron Radiation Emission Spectroscopy (CRES)

CRES of trapped electrons from tritium ß-decay in homogeneous strong magnetic field B

Project 8 – a novel spectroscopic approach

kin e e

E m B e

,

) (      w  w

 precise measurement of w yields electron kinetic energy Ee,kin

combined antenna signal

trapped electron T2 gas

Dw ~ 1 / ts sampling time ts ~ several µs (magnetic bottle)

B-field

G. Drexlin – direct neutrino mass measurement

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 first detection of cyclotron radiation from a single keV electron

Project 8 – single electron history

electron looses energy

nset w  initial 83mKr electron E┴ (30 keV)

scattering off residual gas: energy loss & change of pitch angle DE = 14 eV Time (ms) 0 1 2 3 4 5 Frequency – 24 GHz (MHz)

792 790 788 786 784 782 780 778

1 fW synchrotron energy loss

83mKr

G. Drexlin – direct neutrino mass measurement

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Project 8 – a staged approach

 Phase – II: 2015-2019 - tritium CRES demonstrator first tritium data 2018 several days of runs  Phase – I: 2010-2016 – proof-of-principle test measurements with 83mKr CRES observed for first time fitted ß-decay endpoint: E0 = (18.526 ± 0.09) keV new 2019 campaign to begin soon (100 d)

G. Drexlin – direct neutrino mass measurement

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Project 8 – the future

 Phase – III: … – a large volume demonstrator based on multi-antenna array in MRI tritium spectrum for m(ne) ~ 2 eV

G. Drexlin – direct neutrino mass measurement

cracking cooling selector low-field seekers decay volume

 Phase – IV: … – towards an atomic tritium source R&D for an atomic tritium source (Ioffe trap) goal: inverted mass hierarchy for m(ne) 200 cm³

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KATRIN

G. Drexlin – direct neutrino mass measurement

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KATRIN overview: 70 m long beamline

Windowless Gaseous Tritium Source cryostat Main Spectrometer cryogenic differential pumping RS

G. Drexlin – direct neutrino mass measurement

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MAC-E principle: high-resolution tritium ß-spectroscopy

µ = E┴ / B = const.

solenoid detector electrode

Bmax

solenoid

Us Bs U0 Bmin  Magnetic Adiabatic Collimation & Electrostatic Filter: adiabatic conversion E┴ → E‖

electron from source

T2

G. Drexlin – direct neutrino mass measurement

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 MAC-E filter characteristics well understood (also used to study plasma)

response to quasi-monoenergic electrons

L3-32 line: 30.47 keV retarding energy (eV)

3.0 2.5 2.0 1.5 1.0 30466 30470 30474 30478 measurem. fit result

diff. shape

differential rate (cps/eV)

1000 800 600 400 200

E B B E E   D

max min

filter width

G. Drexlin – direct neutrino mass measurement



E = 32.15 keV E = 9.4 keV



L3-32

rel. rate

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„First Tritium“ FT (2-week engineering run in mid-2018)

 First Tritium:

KATRIN Collab., “First operation of the KATRIN experiment with tritium”, to be subm. to Eur. Phys. J. C

deep scan possible due to „low“ ß-activity c2 = 13.8 for 18 dof

low tritium concentration:

~1% DT and ~99% D2

functionality of all system components 

at nominal rd (5∙1017 cm-2)

G. Drexlin – direct neutrino mass measurement

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KATRIN neutrino mass campaign #1

 4-week long measuring campaign in spring 2019 with high-purity tritium

April 10 – May, 13 2019

780 h

high-purity tritium (eT = 97.5 %) laser-Raman
high source activity:

2.45 ∙ 1010 Bq

high-quality data collected
full analysis chain using two

independent methods

target: first neutrino mass result at TAUP 2019
G. Drexlin – direct neutrino mass measurement

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KATRIN neutrino mass campaign #1

G. Drexlin – direct neutrino mass measurement

column density rd (1017 mol. cm-2)

rel. frequency

1.08 1.10 1.12 1.14 ± 2.4 %  first ever large-scale throughput of high-purity tritium in closed loops

high isotopic tritium purity

 T2 (95.3%), HT (3.5 %), DT (1.1%)

22% of nominal source activity (column density)

 limits effects due to radiochemical reactions of T2 (initial „burn in“ effect)

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tritium scanning – strategy

G. Drexlin – direct neutrino mass measurement

 274 scans of tritium ß-decay sepctrum:

[ E0 – 40 eV , E0 + 50 eV]
alternating up- / down- scans
2 h net scanning time
analysis: 27 HV set points

E0  MTD maximises n-mass sensitivity FSD bg-slope

focus on region close to E0

single tritium scan and fit

22 HV set points 5 HV set points

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modelling of experimental data

𝑆 𝑟𝑉 = 𝐵𝒕 ∙ 𝑂𝑼

𝑟𝑉 𝐹𝟏

𝑆ß( 𝐹, 𝑛𝟑(𝝃𝒇)) ∙ 𝑔 𝐹 − 𝑟𝑉 𝑒𝐹 + 𝑆𝒄𝒉  ß-spectrum ⊗ response function integral ß-decay spectrum R(qU) Rß(E,m2(ne))

response function f

1.0 0.8 0.6 0.4 0.2 0.0

f(E-qU)

surplus energy E-qU (eV)

10 20 30 40 50

G. Drexlin – direct neutrino mass measurement

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G. Drexlin – direct neutrino mass measurement

tritium scanning – fitting of spectrum

 fit of integrated experimental energy spectrum to theoretical model with 4 free parameters background rate Rbg endpoint energy E0

leave parameters As and E0

unconstrained ´shape-only´ fit signal amplitude As  merged data set

combine all 274 scans:

excellent stability of all fitted ß-decay endpoints E0 (s = 0.25 eV) neutrino mass square m2(ne)  “stacking“ of events at mean HV set-point (excellent reproducability: RMS = 34 mV)

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Integral tritium ß-decay spectrum

 High-statistics ß-spectrum

G. Drexlin – direct neutrino mass measurement
2 million events in

in 90-eV-wide interval (522 h of scanning)

excellent goodness-of-fit

c2 = 21.4 for 23 d.o.f. (p-value = 0.56)  bias-free analysis

blinding of FSD
full analysis chain first on

MC data sets

final step: unblinded FSD

for experimental data

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analysis chain & n-mass result

G. Drexlin – direct neutrino mass measurement

 two independent analysis methods to propagate uncertainties & infer parameters

Covariance matrix:

covariance matrix + c2-estimator

MC propagation:

105 MC samples + likelihood (-2 ln 𝓜)

both methods agree to a few percent

𝑛𝟑 𝜉𝒇 = −1.0 + 0.9 − 1.1 eV𝟑 (90% CL)

E0 = (18573.7 ± 0.1) eV  Q-value : (18575.2 ± 0.5) eV Q-value [DM(3H,3He)]: (18575.72 ± 0.07) eV  n-mass and E0: best fit results

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systematics breakdown

 well-understood systematics budget ssyst (with ssyst < sstat)

total systematic uncertainty budget ssyst = 0.32 eV2

1-s uncertainty on mn

2 (eV2)

final state distribution energy loss distribution HV „stacking“ B-field values background slope non-Poisson bg. part inelastic scattering

total statistical uncertainty budget sstat = 0.97 eV2

0.00 0.05 0.10 0.15 0.20 0.25 0.30

G. Drexlin – direct neutrino mass measurement

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systematics breakdown

 well-understood systematics budget ssyst based on only 4 weeks of data

total systematic uncertainty budget ssyst = 0.32 eV2

factor 6 1-s uncertainty on mn

2 (eV2)

final state distribution energy loss distribution HV „stacking“ B-field values background slope non-Poisson bg. part inelastic scattering

total statistical uncertainty budget sstat = 0.97 eV2

factor 2

0.00 0.05 0.10 0.15 0.20 0.25 0.30

G. Drexlin – direct neutrino mass measurement

improves on Mainz/Troitsk by

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KATRIN result and expectation

 best-fit result corresponds to a 1-s statistical fluctuation to negative m2(ne)

G. Drexlin – direct neutrino mass measurement

p-value = 0.16

exp. result:
1.0 eV2

MC ensemble

p-value is derived

from 13 000 MC samples with m2(ne) = 0 and properly fluctuated sstat and ssyst

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neutrino mass upper limit

 confidence belts: procedures of Lokhov and Tkachov (LT) + Feldman and Cousins (FC) m(n) < 1.1 eV (90% CL)

G. Drexlin – direct neutrino mass measurement
KATRIN upper limit on

neutrino mass: m(n) < 0.8 eV (90% CL) < 0.9 eV (95% CL)

for this first result we follow the

robust LT method

LT yields experimental sensitivity

by construction for m2(ne) < 0 LT FC

A.V. Lokhov, F.V. Tkachov, Phys. Part. Nucl. 46 (2015) 347

M. Aker et al. (KATRIN Collab.), An improved upper limit on the neutrino mass from a direct kinematic method by KATRIN, to be subm. to PRL today

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KATRIN – future plans

 KATRIN near- and long-term future : R&D works on ToF-technique for differential tritium scanning

further reduction of background

from decays of Radon & Rydberg atoms  spectrometer bake-out successful   upgraded aircoil system  „shifted analysis plane“ (SAP) bg-studies & tritium scans soon sensitivity m(ne) = 0.2 eV (90% CL) 0.35 eV (5s)

1000 days of measurements at

nominal rd (5 ∙ 1017 molecules cm-2) 3 tritium campaigns (65 days each) per calendar year

further reduction of systematics

energy loss via egun in ToF modus, …

G. Drexlin – direct neutrino mass measurement

SAP

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1950 1960 1970 1980 1990 2000 2010 2020

calendar year neutrino mass sensitivity (meV)

106 105 104 103 102 101

future Moore´s law of direct n-mass sensitivities

G. Drexlin – direct neutrino mass measurement

KATRIN 2024: m(ne) < 0.2 eV (90% CL)

r = 0.35 eV (5 s)

quasi-degenerate masses  KATRIN 2019 – 2024: a new, much steeper slope for Moore´s law KATRIN 2019 m(ne) < 1.1 eV (90% CL)

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SEARCH FOR KEV STERILE NEUTRINOS

G. Drexlin – direct neutrino mass measurement

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Tritium ß-decay and dark fermions

0 2.5 5 7.5 10 12.5 15 17.5

electron energy (keV) ) ( d dN sin ) ( d dN cos d dN

2 2 sterile s active s

m E m E E      

nMSM

Perseus galaxy cluster

 BSM particles (sterile neutrinos, light fermionic DM) in keV-mass scale would produce a ´kink´ in the ß-spectrum

nly active

active and sterile sterile only

ms = 10 keV sin2  = 0.2

G. Drexlin – direct neutrino mass measurement
cover tiny couplings (~10-7)  left-right coulings (Rodejohann)
cover entire phase space (masses up to 18 keV)

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Science reach of KATRIN with new detector array

 estimated KATRIN sensitivity and SDD layout of TRISTAN

TRISTAN – TRitium Investigation on STerile (A) Neutirnos

G. Drexlin – direct neutrino mass measurement
S. Mertens et al., arXiv: 1810.06711

SDD pixel SDD module SDD full array

msterile (keV)

stat. stat.+syst.

Holzschuh 99 Troitsk 17 Hiddemann 95

current detector

1016 electrons, TRISTAN

sin2 

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Conclusion

KATRIN: first neutrino mass result mn < 1.1 eV (90 % CL) 3 cycles / year P8: first tritium CRES spectrum ECHo: goal: m(ne) < 20 eV in 2020 HOLMES: significant R&D progress  major experimental progress of direct kinematic methods since NEUTRINO 2018!

G. Drexlin – direct neutrino mass measurement

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THANK YOU!

G. Drexlin – direct neutrino mass measurement

thank you to L. Gastaldo, J. Formaggio, N. Oblath, A. Nucciotti this talk is dedicated to V.M. Lobashev & E.W. Otten

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G. Drexlin – direct neutrino mass measurement

ADDITIONAL TRANSPARENCIES

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ß-source requirements kinematics: short t½ & low E0 (super-) allowed transition good understanding of final state high isotopic purity & source stability well-established procurement method

Complementarity: tritium ß-decay & EC of 163Ho

e-

nly two isotopes of choice:

tritium & holmium T2 (3HeT)+ e- (3H)2 → 3HeT+ + e- + ne

_

ne

_

163Ho + e- → 163Dy* + ne

ne

G. Drexlin – direct neutrino mass measurement

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Complementarity: tritium ß-decay & EC of 163Ho

e-

nly two isotopes of choice:

tritium & holmium

G. Drexlin – direct neutrino mass measurement

3H: super-allowed

E0 18.6 keV t1/2 12.3 y molecular  atomic (R&D) 4 × 108 atoms for 1 Bq

163Dy*: line width

E0 2.8 keV t1/2 4570 y 2 × 1011 atoms for 1 Bq atomic, in solid state, embedded in (ordered) crystal ß-source requirements kinematics: short t½ & low E0 (super-) allowed transition good understanding of final state high isotopic purity & source stability well-established procurement method

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ß-detection requirements cover large solid angle (~ 2) very low background rate at E0 high energy resolution (~ eV) short dead time, no pile up MAC-E filter

min. longitudinal ß-energy E‖

DE = 0.9 eV (100% transm.)

direct neutrino mass experiments – read-out

cyclotron radiation

max. transversal ß-energy E┴

DE = 2-3 eV (FWHM) thermal µ-calorimeter released decay-energy DE ~ 5 eV (FWHM) metallic magnetic calorimeter released decay-energy DE = 2-5 eV (FWHM) MAC-E filter: highest energy resolution

G. Drexlin – direct neutrino mass measurement

electron energies calorimeter: source  detector

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MAC-E filter

min. longitudinal ß-energy E‖

DE = 0.9 eV (100% transm.)

direct neutrino mass experiments – the projects

cyclotron radiation

max. transversal ß-energy E┴

DE = 2-3 eV (FWHM) thermal µ-calorimeter released decay-energy DE ~ 5 eV (FWHM) metallic magnetic calorimeter released decay-energy DE = 2-5 eV (FWHM)

G. Drexlin – direct neutrino mass measurement

PTOLEMY: R&D efforts to combine techniques

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HOLMES – status & plans

 HOLMES source production and purification: 130 MBq available for tests and experiments

DEFWHM = (4.9 ± 0.1) eV

 Detector arrays - characterization:

very good single pixel performance
operating microwave SQUID multiplexing

 timeline

proof-of-concept (2013-18), 64 channels, 1 month running
full scale (2019ff), 1000 channels, 3 years
upcoming: loading of TES arrays with Ho-163
G. Drexlin – direct neutrino mass measurement

SLIDE 50

KIT-KCETA 50

Sept. 13, 2019

1 year live time

Insufficient e- lifetime T2 final states δB/B ~ 10-7

effective volume (m3) 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 103 90% CL mass limit (eV)

estimated sensitivities (statistics only)

3 × 1011 T2-decays

PRELIMINARY 10 1 0.1

dB/B ~ 10-7

6 4 2 6 4 2 6 4 2

insufficient e- lifetime T2 final states

1 × 1012 decays of atomic T 3 × 1013 T2-decays 3 × 1012 T2-decays

1 s for observable m2(ne) (eV) 100 10 1 0.1 0.01 0.001 40 meV 100 meV

adopted from P8 Collab.

T2 T

G. Drexlin – direct neutrino mass measurement

SLIDE 51

KIT-KCETA 51

Sept. 13, 2019

retarding energy (eV)

tritium scanning

 excellent stability of scanning

ver entire 4-week period

s = 0.254 eV

fits to ß-decay endpoints E0
f all 274 tritium scans:

 Gaussian distribution time (hours) p-value = 0.51

G. Drexlin – direct neutrino mass measurement

SLIDE 52

KIT-KCETA 52

Sept. 13, 2019

systematics: background

 background due to neutral, excited atoms in active flux-tube volume

~50%: ionisation of Rydberg states due to BBR

 purely Poisson component scan #

~50%: a-decays of 219Rn atoms from NEG pump

 with small non-Poisson part bg-rate (cps)

G. Drexlin – direct neutrino mass measurement

SLIDE 53

KIT-KCETA 53

Sept. 13, 2019

neutrino mass upper limit

 calculation of confidence belts m(n) < 1.1 eV (90% CL)

G. Drexlin – direct neutrino mass measurement
procedures of Lokhov and Tkachov (LT) + Feldman and Cousins (FC):

no empty confidence intervals for fluctuations into region m2(ne) < 0

KATRIN upper limit on

neutrino mass (LT)

KATRIN upper limit on

neutrino mass (FC) m(n) < 0.8 eV (90% CL) < 0.9 eV (95% CL)

SLIDE 54

KIT-KCETA 54

Sept. 13, 2019

electron gun to measure electron energy losses

 Angular selective precison egun: determine nelastic energy losses in source & rd egun

n.c. magnets

s.c. magnet

2nd containment

egun during commissioning phase

well-defined pitch angle D
narrow energy spread DE
excellent stability at high rates

SLIDE 55

KIT-KCETA 55

Sept. 13, 2019
G. Drexlin – direct neutrino mass measurement

systematics due to column density

 column density rd – in situ measurement of transmission function with egun surplus energy (eV) rd s = 0.403 with 0.6 % uncertainty rd = 1.1 ∙ 1017 molecules cm-2 with 0.8 % uncertainty egun data

norm. residuals

rate (kcps) 1.4 1.3 1.2 1.1 1.0 2

2

SLIDE 56

KIT-KCETA 56

Sept. 13, 2019

Concept of shifted analysis plane

G. Drexlin – direct neutrino mass measurement

SLIDE 57

KIT-KCETA 57

Sept. 13, 2019

10 8 6 4 2 event ensemble Nev

EC on holmium – sensitivity

 requirements for sub-eV sensitivity 1010 1012 1014 1016

G. Drexlin – direct neutrino mass measurement

sensitivity on m(ne) in eV (90% CL)

Based on n2018 transparency by L. Gastaldo

good statistics in endpoint region:

Nev > 1014 → overall A ~ 1 MBq

limit unresolved pile-up (fpu ~ a · tr)

fpu < 10-6 for tr < 1 µs  limit pixel a ~ 10 Bq

very good energy resolution at endpoint

DE(FWHM) < 3 eV

very low background level