[PPT] - Neutrino Mass Experiments Patrick Decowski decowski@nikhef.nl PowerPoint Presentation

SLIDE 1

Neutrino Mass Experiments

Patrick Decowski decowski@nikhef.nl

SLIDE 2

Observable Relies on ΛCDM Majorana Kinematics

Cosmology 0νββ β decay / EC

Measuring Neutrino Mass

SLIDE 3

Direct Measurement Using Weak Decays

Beta Decay (Tritium) Electron Capture (Holmium)

H He

Ho D
low end-point

→ relatively large spectrum deformation

short life

→ small source amount / less scattering in source

(super) allowed transition → matrix element reliably calculable
simple molecular

→ molecular states calculable

high isotopic purity
source stability
established procurement

Wish List for Direct Measurements

Only two isotopes of choice:

E0 = 18.6 keV 1/2 = 12.3 y super-allowed QEC = 2.8 keV 1/2 = 4570 y

[Slide S. Enomoto]

SLIDE 4

Neutrino Mass Measurements with Weak Decays

Beta Decay (Tritium)

Electron Capture (Holmium)

X-ray Auger electron

H He

Ho D

De-excitation Spectrum

No capture from K and L

beta electron

Electron Spectrum

(QEC = 2.8 keV) (E0 = 18.6 keV)

[Slide S. Enomoto]

Dy = Dysprosium

KATRIN

SLIDE 5

Electron Spectroscopy with Electro-Static Filter

6

electron counter electro-static retarding potential tritium source e e eU U

Problem: only small fraction of electrons reach this → guiding magnetic field

[Slide S. Enomoto]

SLIDE 6

Electron Spectroscopy with Electro-Static Filter

7

electro-static retarding potential electron counter guiding magnetic-field

Problem: only Eparallel is measured → adiabatic collimation Eparallel / Etransversal depends on initial emission angle

tritium source eU U

[Slide S. Enomoto]

SLIDE 7

Electron Spectroscopy with Electro-Static Filter

8

electro-static retarding potential eU electron counter guiding magnetic-field

⇒ magnetic moment conserves: ⇒ collimation

const

B

E

reduce magnetic field adiabatically

tritium source U

[Slide S. Enomoto]

SLIDE 8

MAC-E (Magnetic-Adiabatic-Collimation Electro-static) Filter

9

eU Bmin electron counter Bmax

Energy resolution is determined by B-Ratio Adiabatic Transmission

(constant magnetic moment) Retarding Potential Adiabatic Transmission (or blocking)

min

ma const

[Slide S. Enomoto]

SLIDE 9

KATRIN Experiment

1011 Bq Gaseous Tritium Source

Tritium Retention (electrons guided by B) Electron Counter (~10 mHz)

0.9 eV Resolution MAC-E Filter

KArlsruhe TRItium Neutrino Experiment

11

Calibration E-Gun

located at Karlsruhe Institute of Technology, Karlsruhe, Germany
design sensitivity: m(e) < 0.2 eV (90%CL, 3 years)

Injection 1.8 mbar l/s 10－14 mbar l/s

SLIDE 10

KATRIN

70m

SLIDE 11

Results

m2(νe) = − 1.0+0.9

−1.1 eV2

[1σ fluctuation to negative result] Best-fit:

KATRIN upper limit on neutrino mass: mν < 1.1 eV (90% CL) Only 4 weeks of data!

arXiv:1909.06048

By 2024: mν < 0.2 eV (90% CL)

r = 0.35 eV (5σ)

SLIDE 12

Neutrinoless Double Beta Decay

SLIDE 13

Double beta decay Isotopes

A second-order process only detectable if first-order beta decay is energetically forbidden

(A,Z) (A,Z+1) (A,Z+2)

even-even

ββ

136 53 I

Ba Xe

54 136 55 Cs 136 136 56

La

136 57

Ce

136 58

Pr

136 59

+

+ (MeV) 1 2 3 4 5 6 7 8 9

A=136

SLIDE 14

Neutrinoless Double Beta Decay

> > Nuclear Process (A, Z) (A, Z+2) W- W- e- e- νi νi Uei Uei

Mν 6= |∆L| = 2

But what if ν is Majorana?

SLIDE 15

Candidate 0ν2β Nuclei

Candidate Q[MeV] %Abund

48Ca → 48Ti

4.271 0.187

76Ge → 76Se

2.04 7.8

82Se → 82Kr

2.995 9.2

96Zr → 96Mo

3.35 2.8

100Mo → 100Ru

3.034 9.6

110Pd → 110Cd

2.013 11.8

116Cd → 116Sn

2.802 7.5

124Sn → 124Te

2.228 5.64

130Te → 130Xe

2.53 34.5

136Xe → 136Ba

2.479 8.9

150Nd → 150Sm

3.367 5.6

[Candidates with Q>2 MeV]

Natural abundance of 0ν2β candidates is low → enrichment necessary

Candidates are even-even nuclei (A,Z) (A,Z+1) (A,Z+2)

even-even

ββ

SLIDE 16

Detecting 0ν2β Decay

0ν2β 2ν2β

Ee/Q

Without energy resolution With energy resolution

General approach: detect the two final-state electrons
Signature: Two simultaneous electrons with summed energy Qββ, the Q-value for the ββ decay

in the isotope of study

2ν2β : (A, Z) → (A, Z + 2) + 2e− + 2νe 0ν2β : (A, Z) → (A, Z + 2) + 2e−

SLIDE 17

2ν2β has been measured

Conserves lepton number
Does not discriminate between Dirac and Majorana

neutrinos

Not sensitive to neutrino mass scale
Nevertheless: slow process!

(T 2ν

1/2)−1 = G2ν(Q, Z)|M2ν|2

Phase Space factor Nuclear Matrix Element

Isotope T1/22ν [yr]

48Ca

4.2±1.0 x 1019

76Ge

1.5±0.1 x 1021

82Se

0.92±0.07 x 1020

96Zr

2.0±0.3 x 1019

100Mo

7.1±0.4 x 1018

116Cd

3.0±0.2 x 1019

128Te

2.5±0.3 x 1024

130Te

0.9±0.1 x 1021

136Xe

2.165±0.054 x 1021

150Nd

7.8±0.8 x 1018

238U

2.0±0.6 x 1021 [2ν2EC on 124Xe: 1.8 x 1022 yr]

SLIDE 18

What mass does 0ν2β measure?

(T 0ν

1/2)−1 = G0ν(Q, Z)|M0ν|2mββ⇥2

Effective Majorana mass:

Phase Space factor: Calculable Nuclear Matrix Element: Hard to calculate

Interesting physics

Where Uei elements from the Lepton Mixing Matrix

[coherent sum]

hmββi =

3

X

i=1

U 2

eimi

SLIDE 19

Nuclear Matrix Elements

Model dependence: spread of 2-3x for

each isotope

No significant preference for particular

isotope

(T 0ν

1/2)−1 = G0ν(Q, Z)|M0ν|2mββ⇥2

76Ge 136Xe

SLIDE 20

Effective Majorana Mass

θ12 = 33.580

δ

θ13 = 00

δ

θ12 = 33.58 δ θ13 = 8.33 δ

Normal Inverted

θ13 non-zero

KATRIN

S. Elliot, Mod. Phys. Lett. A 27, 1230009 (2012)

KKDC claim in 76Ge Next-generation of 0ν2β expt: few 100kg Future 0ν2β expt: ton-scale

SLIDE 21

Experimental sensitivity

Detector Efficiency Isotopic Fraction Atomic Mass Background Rate Detector Mass Running Time Detector Resolution

T 0ν

1/2 ∝ a

A

Mt

b∆E T 0ν

1/2 ∝ ✏ a

AMt

No experimental background: With experimental background:

SLIDE 22

Backgrounds

The signal level of the experiments is few cnts/(ton-year)
Background control critical
Typical backgrounds involved
Contamination from U and Th decay-chain isotopes
Compton-scattered ɣ rays, β and α particles
Cosmogenic muon induced backgrounds
Activation of shielding, source material etc.

0ν2β experiments are ultra-clean and conducted deep under ground log(exposure) log(sensitivity)

BG free: ~t BG: ~t1/2 Systematics

=mass x time For any rare event expt:

SLIDE 23

Q-val and Background

Q [MeV] 2 3 4

76Ge 130Te 136Xe 100Mo 82Se

5

150Nd 96Zr 48Ca

Natural radioactivity (40K, 60Co,234mPa, external 214Bi and 208Tl…)

214Bi and Radon 208Tl (2.6 MeV γ line) and Thorium

γ from (n,γ) reactions Surface or bulk contamination in α emitters Cosmogenic production

SLIDE 24

Generally Two Techniques

Source ≠ Detector Source = Detector β1 β2 β2 β1

Source Detector Detector Detector

Pros: +Easy to change source isotope +Background mitigation +Topology Pros: +Energy resolution +Mass +Detection Efficiency Cons:

Mass
Detection Efficiency

Cons:

Background mitigation
Topology

SLIDE 25

Incomplete (and outdated) overview of experiments

Isotope Experiment Technique Mass Enriched Qββ [MeV] Start/Stage

130Te

Cuoricino TeO2 bolometers 40.7kg No 2.6 Done

82Se, 100Mo

NEMO-3 tracko-calo 0.9kg/6.9kg Yes 3.37 Done

136Xe

EXO LXe [tracking] 170kg 80% 2.458 Done

76Ge

GERDA Phase I/II Ge diodes in LAr 18kg/35kg 86% 2.04 2011/2015

76Ge

Majorana Ge diodes 30kg 86% 2.04 2015

136Xe

KamLAND-Zen Isotope in LS 380/750kg 90% 2.458 2011/2019

130Te

CUORE TeO2 bolometers 204kg No 2.53 2016

130Te

SNO+ Isotope in LS 750kg No 2.53 2020

136Xe

nEXO LXe [tracking] 5000kg 80% 2.458 2027?

76Ge

LEGEND Ge diodes in LAr 200/1000kg 86% 2.04 ?

82Se, 150Nd

SuperNEMO tracko-calo 7kg/100kg Yes 3.37 ?

136Xe

NEXT GXe 100kg yes 2.458 ?

116Cd

COBRA CdZnTe semicond No 2.8 Prototype

48Ca

CANDLES CaF2 cryst in LS 0.35kg No 4.27 Prototype

82Se

Lucifer bolom+scintill

100Mo

MOON tracking 1t No 3.03 Prototype DARWIN

SLIDE 26

KamLAND(-Zen) detector

1 kton Scintillation Detector
6.5m radius balloon filled with:
20% Pseudocumene (scintillator)
80% Dodecane (oil)
PPO
34% PMT coverage
~1300 17” fast PMTs
~550 20” large PMTs
Water Cherenkov veto
Operational since 2002

Water Cherenkov Outer Detector 1800 m3 Buffer Oil

20 m

}

3200 m3

SLIDE 27

Mini-Balloon

Requirements
Chemical compatibility with LS
Mechanically strong, low radioactivity
Barrier against Xe:
loss < 220g/yr
Transmission of scintillation light
99.4% at 400nm

Corrugated nylon tube (7 m) PEEK connector Vectran strings (12) Tube Cone Straps (12) Balloon (24 gores) Belt and polar cap

Material: 25 μm thick ultra-

pure nylon

U/Th/K ≲ 10-12 g/g
1/4 & full scale tests in air and

water

1.54m

SLIDE 28

Mini-Balloon Construction: May-Aug 2011

Near Sendai

SLIDE 29

Difference in refractive index LS and Xe-LS

29

SLIDE 30

+Well-understood detector
+Highly pure, self-shielding environment
+Large ββ source mass, scalable
-Relatively poor energy resolution
-No particle identification

KamLAND-Zen advantages & disadvantages

T 0ν

1/2 ∝ a

A

Mt

b∆E

SLIDE 31

KamLAND-Zen Timeline

Phase 1

Sept ’11:Start

Visible Energy (MeV) 1 2 3 4 Events/0.05MeV

1

10 1 10

2

10

3

10

4

10

5

10

Th

232

U +

238

Kr

85

Bi +

210

+ IB/External Spallation Data

Visible Energy (MeV) 1 2 3 4 Events/0.05MeV

1

10 1 10

2

10

3

10

4

10

5

10

Th

232

U +

238

Kr

85

Bi +

210

+ IB/External Spallation Data

Xe 2

136

T 2ν

1/2 = 2.30 ± 0.02 (stat) ± 0.12 (sys) × 1021 yr

Visible Energy (MeV) 1 2 3 4 Events/0.05MeV

1

10 1 10

2

10

3

10

4

10

5

10

Bi

208

Y

88

Ag

110m

Th

232

U +

238

Kr

85

Bi +

210

+ IB/External Spallation Data

Xe 2

136

Visible Energy (MeV) 1 2 3 4 Events/0.05MeV

1

10 1 10

2

10

3

10

4

10

5

10

Bi

208

Y

88

Ag

110m

Th

232

U +

238

Kr

85

Bi +

210

+ IB/External Spallation Data Total

Xe 2

136

Total U.L.)

(0
Xe 0

136

(90% C.L. U.L.)

T0ν1/2 > 1.9 x 1025 yr (90% CL)

90 kg-yr

KamLAND-Zen Collaboration, Phys.Rev.Lett. 110 (2013) 062502

Phase 1 2011 2012 2013 2014 2015

110mAg due to Fukushima-I

nuclear fallout

SLIDE 32

Visible Energy (MeV) 1 2 3 4 Events/0.05MeV

1

10 1 10

2

10

3

10

4

10

5

10

Phase I to Phase II Improvements

10C 110mAg

No Xe in MiniBalloon

Sept ’11:Start 90 kg-yr purification

Phase 1

Remove radioactive impurities with

Xe-LS purification

long distillation campaign

+ new LS

Increase the amount of Xe
320kg → 383kg (+20%)
Spallation cut after muon

→ 10C rejection

muon-neutron-10C (τ=27.8s) triple

coincidence

Phase 1 Phase II 2011 2012 2013 2014 2015

504 kg-yr purification

SLIDE 33

110mAg Background Reduction

208Tl (Th) 214Bi

Balloon

134Cs 134Cs 137Cs 137Cs 214Bi 208Tl (Th) 110mAg (ballon) 110mAg (ballon) 110mAg (Xe-LS)

Date Dec 2013 Jan 2014 Feb 2014 Mar 2014 Apr 2014 0.5 1

Ag BG to

2.2 < E < 3.0 MeV, R < 1 m

Date Oct 2011 Nov 2011 Dec 2011 Jan 2012 Events/Day 0.5 1

2.2 < E < 3.0 MeV, R < 1 m

2.2 < E < 3.0 MeV, R<1m 2.2 < E < 3.0 MeV, R<1m

Phase 1 First 115d of Phase II

110mAg BG reduced < 1/10

events/day R<1m events/day

SLIDE 34

KLZ-400 Phase 2 Data

)

2

(m

2

+Y

2

X 1 2 3 4 Z (m) 2

1
1

2 Bi Event Rate (Events/Bin)

214

Simulated

1 10

2

10

3

10

4

10

5

10

6

10

2.3 < E < 2.7 MeV

Visible Energy (MeV) 1 2 3 4 Events/0.05MeV

2

10

3

10

4

10

Data

Xe 2

136

Spallation IB/External Total Th

232

U+

238

Po

210

Bi+

210

+ K

40

Kr+

85

+

candidates (data)

214Bi simulation (colz)

KamLAND-Zen Coll, Phys. Rev. Lett. 117, 082503 (2016); arXiv:1605.02889

We use 40 equal-volume bins to account for varying BG: Simultaneous spectral fit in all volume bins Event Selection: i) R < 2m ii) ΔT > 2ms after muons iii) no 214Bi-214Po (τ=237μs) iv) no 212Bi-212Po (τ=0.4μs) v) no reactor neutrinos

SLIDE 35

Results for Phase-2

Runtime(days) 100 200 300 400 500 600 Events/Day 0.1 0.2

New 2ν2β value: T1/22ν = 2.21 ± 0.02 (stat) ± 0.07 (syst) x 1021 yr

Visible Energy (MeV) 1 2 3 4 Events/0.05MeV

1

10

1 10

2

10

3

10

4

10

Data Total U.L.)

(0
Xe 2

136

Bi

210

Th+

232

U+

238

K

40

Kr+

85

Po+

210

+ IB/External Spallation

Visible Energy (MeV) 1 2 3 4 Events/0.05MeV

1

10

1 10

2

10

3

10

4

10

Data Total Total U.L.)

(0
Xe 2

136

Xe 0

136

(90% C.L. U.L.) Bi

210

Th+

232

U+

238

K

40

Kr+

85

Po+

210

+ IB/External Spallation

Period 1 Period 2

2.4 2.6 2.8 3 Events/0.05MeV 1 2 3 4 Period-1 Visible Energy (MeV) 2.4 2.6 2.8 3 Events/0.05MeV 1 2 3 4 Period-2

2.3 < E < 2.7 MeV, R<1m

R<1m

New 0ν2β limit: T0ν1/2 > 9.2 x 1025 yr

[sens: > 5.6 x 1025 yr] Period 2

504 kg-yr exposure of 136Xe

SLIDE 36

Background Estimates

Period-1 Period-2 (270.7 days) (263.8 days) Observed events 22 11 Background Estimated Best-t Estimated Best-t

136Xe 2νββ

5.48
5.29

Residual radioactivity in Xe-LS

214Bi (238U series) 0.23 ± 0.04

0.25 0.028 ± 0.005 0.03

208Tl (232Th series)

0.001
0.001

110mAg

8.5
0.0

External (Radioactivity in IB)

214Bi (238U series)

2.56
2.45

208Tl (232Th series)

0.02
0.03

110mAg

0.003
0.002

Spallation products

10C

2.7 ± 0.7 3.3 2.6 ± 0.7 2.8

6He

0.07 ± 0.18 0.08 0.07 ± 0.18 0.08

12B

0.15 ± 0.04 0.16 0.14 ± 0.04 0.15

137Xe

0.5 ± 0.2 0.5 0.5 ± 0.2 0.4

2.3 < E < 2.7 MeV, R < 1m

110mAg 214Bi

2ν2β

10C

New Balloon Better σE Improved neutron detection

Next phases:

SLIDE 37

Effective Neutrino Mass

(eV)

lightest

m

4

10

3

10

2

10

1

10 (eV) m

3

10

2

10

1

10 1

IH NH

A 50 100 150

Ca Ge Se Zr Mo Cd Te Te Nd

(eV)

lightest

m

4

10

3

10

2

10

1

10 (eV) m

3

10

2

10

1

10 1

IH NH Xe)

136

KamLAND-Zen (

A 50 100 150

Ca Ge Se Zr Mo Cd Te Te Xe Nd

(T 0ν

1/2)−1 = G0ν(Q, Z)|M0ν|2mββ⇥2

⟨mββ⟩ < 61 - 165 meV

KamLAND-Zen Coll, Phys. Rev. Lett. 117, 082503 (2016); arXiv:1605.02889

SLIDE 38

Future Goals

(eV)

lightest

m

4

10

3

10

2

10

1

10 (eV) m

3

10

2

10

1

10 1

IH NH Xe)

136

KamLAND-Zen (

A 50 100 150

Ca Ge Se Zr Mo Cd Te Te Xe Nd

380kg Xe 750kg Xe New Balloon KamLAND-Zen 400 KamLAND-Zen 800 1000kg Xe KamLAND2-Zen

20 meV 50 meV

Running!

SLIDE 39

GERDA Experiment

Uses 76Ge Diodes
Source = Detector
Housed in a water tank and an

LAr cryostat

In Gran Sasso

SLIDE 40

GERDA Diodes

Signal Backgrounds

T 0ν

1/2 ∝ a

A

Mt

b∆E

SLIDE 41

GERDA II results

Energy (keV) 1000 1500 2000 2500 3000 3500 4000 4500 5000 yr ) ⋅ kg ⋅ counts / ( keV

3 −

10

2 −

10

1 −

10 1 10

2

10

β β

Q K-40 K-42 Bi-214 Bi-214 Tl-208 Po-210 yr ⋅ enriched detectors - 53.9 kg prior to active background rejection after pulse shape discrimination (PSD) after liquid argon (LAr) veto and PSD yr)

21

10 ⋅ = 1.92

1/2

(T β β ν 2

GERDA 18-06

yr ) ⋅ kg ⋅ counts / ( keV

3 −

10

2 −

10

1 −

10 yr ⋅ enriched coaxial - 23.1 kg background level yr limit (90% C.L.)

26

10 ⋅ = 0.9

1/2

T Energy (keV) 1950 2000 2050 2100 2150

3 −

10

2 −

10

1 −

10 yr ⋅ enriched BEGe - 30.8 kg σ 2 ±

β β

Q

T0ν

1/2 > 0.9 × 1026 yr

arXiv:1909.02726 mββ < (0.10 − 0.23) eV

SLIDE 42

Most up to date results

3 −

10

2 −

10

1 −

10 1 (eV)

light

m

3 −

10

2 −

10

1 −

10 1 (eV)

β β

m

GERDA 2018

1 −

10 1 (eV) Σ

3

10

2

10

1

10 1

Cosmology (min.) Cosmology (extd.)

2 −

10

1 −

10 1 (eV)

β

m

3

10

2

10

1

10 1

normal ordering inverted ordering global sensitivity KATRIN (5 yr)

GERDA 18-11

Close to probing Inverted Ordering
At the same time, long baseline oscillation experiments have preference for Normal Ordering :-(

arXiv:1909.02726

SLIDE 43

Using Dark Matter Detectors for 0ν2β

DARWIN Experiment
50t of natural LXe total
136Xe has 8.6% natural abundance
4 tons of 136Xe
But perhaps only inner ~6 tons

usable, rest used for shielding

effectively ~500kg usable

2.6m

SLIDE 44

Q-value (2458.7±0.6) keV
Energy resolution (σ/μ) at Qββ 1%

214Bi → 214Po + e– + γ (2448 keV)

Intrinsic BG only

4.6 events/year within ±3σ

JCAP 01, 044 (2014)

T1/2 > 8.5×1027 yr (140t x yr) T1/2 > 5.6×1026 yr (30t x yr)

current limit (KamLAND-Zen)

Is the neutrino a Majorana particle?

Neutrinoless Double Beta Decay

SLIDE 45

Conclusions

Many experiments dedicated to measure different types of “neutrino mass”
Coming years will bring some interesting measurements!

Mν = ∑

i

mi mββ = ∑

i

U2

ei mi

m2

β = ∑ i

Uei

2 m2 i

Neutrino Mass Experiments

Patrick Decowski decowski@nikhef.nl

Measuring Neutrino Mass

Direct Measurement Using Weak Decays

Neutrino Mass Measurements with Weak Decays

Electron Spectroscopy with Electro-Static Filter

Electron Spectroscopy with Electro-Static Filter

Electron Spectroscopy with Electro-Static Filter

MAC-E (Magnetic-Adiabatic-Collimation Electro-static) Filter

KATRIN Experiment

KATRIN

Results

Neutrinoless Double Beta Decay

Double beta decay Isotopes

A second-order process only detectable if first-order beta decay is energetically forbidden

A=136

Neutrinoless Double Beta Decay

Candidate 0ν2β Nuclei

Candidates are even-even nuclei (A,Z) (A,Z+1) (A,Z+2)

ββ

Detecting 0ν2β Decay

0ν2β 2ν2β

2ν2β has been measured

(T 2ν

What mass does 0ν2β measure?

(T 0ν

hmββi =

X

U 2

Nuclear Matrix Elements

(T 0ν

Effective Majorana Mass

Experimental sensitivity

T 0ν

1/2 ∝ a

A

b∆E T 0ν

1/2 ∝ ✏ a

AMt

No experimental background: With experimental background:

Backgrounds

Q-val and Background

Generally Two Techniques

Incomplete (and outdated) overview of experiments

KamLAND(-Zen) detector

20 m

}

Mini-Balloon

Mini-Balloon Construction: May-Aug 2011

Difference in refractive index LS and Xe-LS

KamLAND-Zen advantages & disadvantages

T 0ν

A

b∆E

KamLAND-Zen Timeline

Phase I to Phase II Improvements

KLZ-400 Phase 2 Data

Results for Phase-2

Background Estimates

Effective Neutrino Mass

Future Goals

GERDA Experiment

GERDA Diodes

T 0ν

A

b∆E

GERDA II results

Most up to date results

Using Dark Matter Detectors for 0ν2β

usable, rest used for shielding

Is the neutrino a Majorana particle?

Neutrinoless Double Beta Decay

Conclusions

m(νe) does not exist!