1. “Neutrino mass determination”
- Florian Fränkle -

2. Outline Neutrino masses Single b-decay experiments
163Ho electron capture experiments
0nbb-decay experiments
Cosmology
Summary
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

3. Neutrino masses ne nm nt m1 m2 m3
Ue1
Um1
Ut1
Ue2
Um2
Ut2
Ue3
Um3
Ut3 =
Neutrino flavour eigenstates are related to neutrino mass eigenstates by the lepton mixing matrix (PMNS)
Neutrino oscillations are sensitive to the differences between the squares of neutrino masses
Two mass ordering scenarios possible
The value of the lightest neutrino mass is unknown
normal
inverted m3 2 m2 m1 m ?
Dmatm. ne nm nt
Dmsol.
mass ordering
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

4. Neutrino masses
Neutrinos are massive particles, but so far there are only upper and lower limits
Absolute neutrino mass scale is one of the big open questions in particle physics, astrophysics and cosmology
Different approaches to determine neutrino mass:
direct measurements
neutrino mass
cosmology
0nbb decay
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

5. Neutrino mass and single b-decay
Fermi theory of b-decay:
b-decay: n → p + e- + ne
Neutrino mass influences energy spectrum of b-decay electrons
Neutrino mass determination via precise measurement of the spectral shape close to the endpoint
Model independent method
b-spectrum for tritium (E0 = 18.6 keV, T1/2 = 12.3 y):
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

6. Cryogenic Pumping sections
The KATRIN experiment
KArlsruhe TRItium Neutrino experiment
Goal: Measure neutrino mass with a sensitivity of 0.2 eV/c² (90% C.L.)
~ 70 m
Pre-Spectro-meter
Differential and
Cryogenic Pumping sections
Main Spectrometer
Detector
Windowless Gaseous
Tritium Source
tritium b-decay
decay rate: /s
T2 pressure: to 10-6 mbar
b-electron transport
tritium retention (factor < 10-12)
energy analysis of b-electrons
resolution keV
pressure < mbar
counting of transmitted b-electrons
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

7. October 14th, 2016 – KATRIN first light
Experiment to Weigh 'Ghost Particles' Starts in Germany
KATRIN celebrates first beam
Experimente zum Wiegen von Neutrinos starten in Karlsruhe
Neutrinos kommen auf die Waage
Experiment starts to find weight of 'ghost particles'
The KATRIN Tritium Neutrino experiment: A giant scale for the tiniest of particles
Forscher geben Startschuss zum Wiegen von Geisterteilchen
Neutrino Mass: Germany’s KATRIN Experiment Aims To Weigh The Universe’s Lightest Particle
Neutrinos auf der Waage
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

8. rear wall electron beam
KATRIN first light
rear wall electron beam
photo-electrons produced via UV light illumination of rear wall (-50 V)
electron source
detector
Start of KATRIN beamline commissioning: for the first time electrons were transported along the complete beamline
Measurement campaign to investigate alignment and ion blocking system
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

9. KATRIN first light – alignment
rear wall electron beam
ELIOTT electron beam
ELIOTT electron beam
rear wall electron beam
90 mm
5 mm
electron sources
detector mm
KATRIN beamline is aligned and in good agreement with simulations
Unobstructed transport of 191 Tcm² flux tube from source to detector
Measurements with 83mKr this summer, start tritium runs in 2018
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

10. Cyclotron Resonance Emission SpectroscopyB
electron
antenna array
Simulated spectrum (105 T2 decays)*
Idea: Measure b-spectrum via coherent cyclotron radiation emitted by an energetic electron in a magnetic field (radiated power about 1 fW)
Frequency of emitted radiation independent of electron pitch angle Q
New form of nondestructive spectroscopy
* B. Monreal, J.A. Formaggio, PHYSICAL REVIEW D 80, (R) (2009), DOI: /PhysRevD
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

11. Project 8
83mKr * ‡
onset frequency → initial energy
energy loss
(cyclotron radiation)
scattering energy loss, changing pitch angle
First detection of single-electron cyclotron radiation (June 2014)
Spectrum generation via event reconstruction
Initial energy resolution (140 eV) could be improved to 3.3 eV (FWHM)
Measure first tritium spectrum in 2017 (mn < 10 – 100 eV)
Long-term goal: large scale experiment with atomic tritium source and 40 meV sensitivity (hierarchy scale)
‡ A.A. Esfahani et. al. “Determining the neutrino mass with cyclotron radiation emission spectroscopy-Project 8”, J. Phys. G: Nucl. Part. Phys. 44 (2017)
* D.M. Asner et. al. “Single-Electron Detection and Spectroscopy via Relativistic Cyclotron Radiation”, Physical Review Letters, 114, (2015), DOI: /PhysRevLett
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

12. Neutrino mass and electron capture
Electron capture: p + e- → n + ne
Neutrino mass affects the de-excitation energy spectrum
Calorimetric measurement of atomic de-excitation (x-rays, Auger electrons, Coster-Kronig transitions) *
163Ho
T1/2: 4570 yr Q(EC): 2.83 keV
MII MI NI
NII
neutrino
calorimeter
electron capture
thermometer
thermal link, readout
heat sink (< 1 K)
* Christian Enss, “Neutrino Mass Determination by Electron Capture in Holmium-163” ECT workshop Determination of the absolute electron (anti-)neutrino mass, Trento
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

13. 163Ho electron capture experiments
magnetic micro-calorimeter (MMC) arrays with microwave squid multiplexing readout
fast rise time (~ 130 ns) and excellent linearity & resolution (DE ~ 5 eV)
transition edge sensors
NuMECS
absorber
163Ho implanted area
Au:Er sensor
pick-up coil *
investigate the electron neutrino mass in the energy range below 1 eV by a high-precision and high-statistics calorimetric measurement
* P.C.-O. Ranitzsch et al., J Low Temp Phys (2012) 167:1004–1014 DOI: /s
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

14. Double b-decay if 0nbb is discovered: lepton number violation
energy spectrum n p e
= ne ne
0nbb n p e ne
energy [Qbb] 1
2nbb
0nbb
if 0nbb is discovered:
lepton number violation
neutrino is its own antiparticle (Majorana particle)
measure of effective neutrino mass mbb
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

15. 0nbb experiments Experiment Isotope Technique AMoRE 100Mo Low-T MMC
CANDLES
48Ca
CaF2 scintillator + veto
CARVEL
48CaWO4 crystal scintillator
CDEX
76Ge
Point contact Ge
COBRA
116Cd, etc
CdZnTe detectors
CUORE/CUORE-0
130Te
TeO2 bolometers
CUPID
130Te, 82Se, 100Mo, 116Cd
Hybrid bolometers
DCBA/MTD
Foils + tracker
EXO200
136Xe
LXe TPC
GERDA
Semicoax / point contact HPGe
KamLAND-Zen
Liquid scintillator
LEGEND
Point contact HPGe
LUCIFER
82Se
ZnSe scintillator bolometer
Majorana Demonstrator
MOON
Foils + scintillator
NEMO
100Mo, 82Se
nEXO
NEXT
High-P TPC
PandaX
SNO+
SuperNEMO
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

16. GERDA ‡
The GERmanium Detector Array (GERDA) searches for neutrinoless double beta decay in 76Ge
Located underground at Gran Sasso National Laboratory
Five detector strings with a total target mass of 20 kg are installed in 64 m³ of liquid argon
Installed LAr scintillation light veto for background suppression after Phase I
Phase II measurements currently ongoing * *
* Matteo Agostini, “First results from Gerda Phase II” Neutrino 2016, London
‡ Christoph Wiesinger, “GERDA meets KATRIN” KATRIN analysis workshop 2016, Munich
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

17. GERDA *
GERDA Phase II is a high-resolution and background-free experiment
Combined Phase I + II sensitivity: ‡
T > 4.0 × 1025 yr (90% C.L), preliminary
1/2 0n
‡ GERDA collaboration, “Background-free search for neutrinoless double-β decay of 76Ge with GERDA” NATURE VOL , DOI: /nature21717
* Matteo Agostini, “First results from Gerda Phase II” Neutrino 2016, London
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

18. KamLAND-Zen *
KamLAND-Zen repurposed the KamLAND liquid scintillator detector for the search of neutrinoless double beta decay in 136Xe
Target mass 383 kg Xe (91 % 136Xe)
Xe purification system
Combined result phase 1 + 2:
1000 t ultra-pure LS
buffer oil
PMTs
water *
T > 1.07 × 1026 yr (90% C.L)
1/2 0n
Detector is currently being upgraded for operation with 750 kg enriched Xe
R&D for future upgrade to 1000 kg Xe in order to cover the region of inverted mass ordering
* Junpei Shirai, “Results and future plans for the KamLAND-Zen” Neutrino 2016, London
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

19. Cosmological data – Planck
CMB temperature power spectrum
neutrino mass constraints * *
Depending on their mass, neutrinos have an effect on the shape of the CMB power spectrum
Model dependent method, combination of different data sets yield different results
* Planck Collaboration, “Planck 2015 results – XIII. Cosmological parameters”, A&A, 594 (2016) A13, DOI: / /
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

20. Summary
Neutrino mass determination is an active field with various experiments using different techniques
Mainz and Troitsk, < 2 eV
ECHo * ‡
GERDA
KATRIN
KamLAND-Zen
Planck
Project 8
tonne-scale experiments
* Based on J. Phys. A.A. Esfahani et al. G: Nucl. Part. Phys. 44 (2017)
‡ based on arXiv: v3
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

21. Backup
xxx yy
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

22. KATRIN – measurement
KATRIN will measure the integrated b-spectrum close to the T2 endpoint E0
The influence of mn is most pronounced a few eV below E0
Optimized measurement time distribution to increase sensitivity
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

23. KATRIN – MAC-E filter
Magnetic Adiabatic Collimation combined with an Electrostatic Filter
magnetic moment:
energy resolution:
Q = 0°
Q = 15°
Q = ° B pe q 1 1 1
transmission
qU0
energy
qU0
qU0
qU0+DE
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

24. internal radioactivity 40K, … external radioactivity
KATRIN – backgrounds
vessel
wire electrodes e H H* H-
210Pb ~ 1 kBq ✓
internal radioactivity
cosmic muons
210Pb, … a g NR e
BBR
field emission e H2
FPD
Penning discharge e e
insulator processes H+ UV
219Rn g
baffle
40K, … external radioactivity
All previously known background processes are efficiently suppressed
Background rate about 50 times larger than design value (10 mcps), presumably due to ionization of Rydberg atoms by black body radiation
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

25. Project 8 – atomic source
J. Phys. G: Nucl. Part. Phys. 44 (2017) (16pp)
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria

26. 0nbb nuclear matrix elements
Florian Fränkle, “Neutrino mass determination” ALPS 2017, Obergurgl, Austria