Neutrinoless Double Beta decay search with 76 Ge status and - - PowerPoint PPT Presentation

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Neutrinoless Double Beta decay search with 76 Ge status and - - PowerPoint PPT Presentation

Nov 23, 2023 259 likes •744 views

Neutrinoless Double Beta decay search with 76 Ge status and prospects with LEGEND Valerio DAndrea on behalf of the LEGEND Collaboration Universit` a degli Studi dellAquila Moriond 2019 Rencontres de Moriond, La Thuile March 16 - 23,

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SLIDE 1

Neutrinoless Double Beta decay search with 76Ge status and prospects with LEGEND

Valerio D’Andrea

  • n behalf of the LEGEND Collaboration

Universit` a degli Studi dell’Aquila

Moriond 2019

Rencontres de Moriond, La Thuile March 16 - 23, 2019

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SLIDE 2

Why search for Neutrinoless Double Beta (0νββ) decay

Powerful method to study the unknown neutrino properties Observation of 0νββ decay implies: neutrino ν has Majorana nature lepton number violation (∆L = 2) determination of ν absolute mass (nuclear model dependent)

d u d u W W e e d u d u W W e e

¯

νe

¯

νe ν

M

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 2 / 20

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SLIDE 3

Why search for Neutrinoless Double Beta (0νββ) decay

Powerful method to study the unknown neutrino properties Observation of 0νββ decay implies: neutrino ν has Majorana nature lepton number violation (∆L = 2) determination of ν absolute mass (nuclear model dependent)

d u d u W W e e d u d u W W e e

¯

νe

¯

νe ν

M

Half life of 0νββ (in case of light Majorana neutrino exchange):

(T 0ν

1/2)−1 =

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 2 / 20

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SLIDE 4

Why search for Neutrinoless Double Beta (0νββ) decay

Powerful method to study the unknown neutrino properties Observation of 0νββ decay implies: neutrino ν has Majorana nature lepton number violation (∆L = 2) determination of ν absolute mass (nuclear model dependent)

d u d u W W e e d u d u W W e e

¯

νe

¯

νe ν

M

Half life of 0νββ (in case of light Majorana neutrino exchange):

(T 0ν

1/2)−1 =G0ν× Phase Space Integral: well known quantity

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 2 / 20

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SLIDE 5

Why search for Neutrinoless Double Beta (0νββ) decay

Powerful method to study the unknown neutrino properties Observation of 0νββ decay implies: neutrino ν has Majorana nature lepton number violation (∆L = 2) determination of ν absolute mass (nuclear model dependent)

d u d u W W e e d u d u W W e e

¯

νe

¯

νe ν

M

Half life of 0νββ (in case of light Majorana neutrino exchange):

(T 0ν

1/2)−1 =G0ν× |M0ν|2× Phase Space Integral: well known quantity Nuclear Matrix Element: most critical ingredient, produces uncertainty in the determination of mββ (quenching problem)

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 2 / 20

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SLIDE 6

Why search for Neutrinoless Double Beta (0νββ) decay

Powerful method to study the unknown neutrino properties Observation of 0νββ decay implies: neutrino ν has Majorana nature lepton number violation (∆L = 2) determination of ν absolute mass (nuclear model dependent)

d u d u W W e e d u d u W W e e

¯

νe

¯

νe ν

M

Half life of 0νββ (in case of light Majorana neutrino exchange):

(T 0ν

1/2)−1 =G0ν× |M0ν|2× (mββ me )2 Phase Space Integral: well known quantity Nuclear Matrix Element: most critical ingredient, produces uncertainty in the determination of mββ (quenching problem) Neutrino Effective Mass: by measuring T 0ν

1/2, mββ can be estimate

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 2 / 20

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SLIDE 7

Search for 0νββ decay

signature: sharp peak at Q-value of the decay

Energy (keV) 500 1000 1500 2000 Counts / keV

1 −

10 1 10

2

10

3

10

yr ⋅ enriched detectors - 53.9 kg yr)

25

10 ⋅ = 1.0

1/2

(T β β ν yr [EPJC 75 (2015) 9])

21

10 ⋅ = 1.93

1/2

(T β β ν 2

GERDA 18-06

Energy (keV) 1800 2000 Counts / keV 2 4

Experimental sensitivity

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 3 / 20

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SLIDE 8

Search for 0νββ decay

signature: sharp peak at Q-value of the decay

Energy (keV) 500 1000 1500 2000 Counts / keV

1 −

10 1 10

2

10

3

10

yr ⋅ enriched detectors - 53.9 kg yr)

25

10 ⋅ = 1.0

1/2

(T β β ν yr [EPJC 75 (2015) 9])

21

10 ⋅ = 1.93

1/2

(T β β ν 2

GERDA 18-06

Energy (keV) 1800 2000 Counts / keV 2 4

Experimental sensitivity in case of background-free: (Nbkg < 1 at full exposure) S ∝ aε · M · t

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 3 / 20

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SLIDE 9

Status of neutrinoless double beta decay search

most recent limits on the half-life, sensitivity and mββ (at 90% C.L.)

isotope T 0ν

1/2 [1025 yr]

S0ν

1/2 [1025 yr]

mββ [meV] experiment

76Ge

9 11 104–228 Gerda

76Ge

2.7 4.8 157–346 Majorana

130Te

1.5 0.7 162–757 CUORE

136Xe

1.8 3.7 93–287 EXO-200

136Xe

10.7 5.6 76–234 KamLAND-Zen

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 4 / 20

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SLIDE 10

Status of neutrinoless double beta decay search

most recent limits on the half-life, sensitivity and mββ (at 90% C.L.)

isotope T 0ν

1/2 [1025 yr]

S0ν

1/2 [1025 yr]

mββ [meV] experiment

76Ge

9 11 104–228 Gerda

76Ge

2.7 4.8 157–346 Majorana

130Te

1.5 0.7 162–757 CUORE

136Xe

1.8 3.7 93–287 EXO-200

136Xe

10.7 5.6 76–234 KamLAND-Zen

⇓ the future goal is reach sensitivities of S0ν

1/2 ∼ 1027–1028 yr and

improve the limit on the effective Majorana neutrino mass to mββ ∼ 10 meV

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 4 / 20

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SLIDE 11

76Ge based 0νββ decay experiments HPGe detectors enriched up to ∼ 88% in the 76Ge ββ emitter (Nat. ∼ 8%) source = detector → high detection efficiency excellent energy resolution (FWHM ∼ 0.1% at Qββ) background-free experiments (Nbkg < 1 at full exposure) → S ∝ M · t

RUNNING M ∼ 40 kg T 0ν

1/2 1026 yr

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 5 / 20

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SLIDE 12

76Ge based 0νββ decay experiments HPGe detectors enriched up to ∼ 88% in the 76Ge ββ emitter (Nat. ∼ 8%) source = detector → high detection efficiency excellent energy resolution (FWHM ∼ 0.1% at Qββ) background-free experiments (Nbkg < 1 at full exposure) → S ∝ M · t

RUNNING M ∼ 40 kg T 0ν

1/2 1026 yr

MID TERM M ∼ 200 kg T 0ν

1/2 1027 yr

LEGEND-200

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 5 / 20

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SLIDE 13

76Ge based 0νββ decay experiments HPGe detectors enriched up to ∼ 88% in the 76Ge ββ emitter (Nat. ∼ 8%) source = detector → high detection efficiency excellent energy resolution (FWHM ∼ 0.1% at Qββ) background-free experiments (Nbkg < 1 at full exposure) → S ∝ M · t

RUNNING M ∼ 40 kg T 0ν

1/2 1026 yr

MID TERM M ∼ 200 kg T 0ν

1/2 1027 yr

LEGEND-200 LONG TERM M ∼ 1 ton T 0ν

1/2 1028 yr

LEGEND-1000

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 5 / 20

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SLIDE 14

The Majorana Demonstrator

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 6 / 20

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SLIDE 15

Majorana Demonstrator

[Adv. High Energy Physics, 365432 (2014)]

  • perating underground at the 4850’ level of the Sanford Underground

Research Facility (SURF) demonstrate background low enough to justify a future 1 ton experiment detectors: p-type point-contact, 29.7 kg of 88% enr. 76Ge, 14.4 kg of natGe energy resolution: 2.5 keV FWHM at 2039 keV (best in the field) low background: 2 independent cryostat made of ultra-clean electroformed Cu and a compact Cu and Pb shield with active muon veto

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 7 / 20

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SLIDE 16

Majorana Demonstrator: background rejection

Multi Site Events

p-type point-contact detectors have a localized weighting potential the ampitude of current pulse is reduced for a multi-site event w.r.t. a single-site event with the same energy

Alpha Background

this background (e.g. 210Po) is on surfaces close to the point contact charge trapped at passivated surface, slowly released into bulk a distinctive waveform allows a high-efficiency cut (99%)

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 8 / 20

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SLIDE 17

Majorana Demonstrator: results

Data releases: 2017 Release: 9.95 kg·yr [PRL 120 132502 (2018)] 2018 Release: 26 kg·yr [Neutrino 2018, arXiv:1902.02299] Full exposure results (26.0 kg·yr) Background: 15.4 ± 2.0 cts/(FWHM·t·yr) Median Sensitivity: S0ν

1/2 = 4.8 · 1025 yr (90% C.L.)

Limit on 0νββ decay: T 0ν

1/2 > 2.7 · 1025 yr (90% C.L.)

Lowest background configuration (21.3 kg·yr): Background: 11.9 ± 2.0 cts/(FWHM·t·yr) ⇒ (4.7 ± 0.8) · 10−3 cts/(keV·kg·yr)

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 9 / 20

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SLIDE 18

The Gerda Experiment

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 10 / 20

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SLIDE 19

Design of the Gerda experiment

location: Laboratori Nazionali del Gran Sasso, ∼ 1500 m of rock → 3500 m.w.e. bare HPGe detectors enriched in 76Ge (86%) in LAr water tank to shield against external radiation with Cherenkov muon veto

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 11 / 20

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SLIDE 20

Gerda detectors

Semi-Coaxial detectors from previous experiments (HdM, IGEX) total mass 17.7 kg energy resolution: 3.6 keV (FWHM) Qββ BEGe detectors produced for Phase II energy resolution: 3.0 keV (FWHM) Qββ better Pulse Shape Discrimination with A/E ratio (= current-amplitude/energy)

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 12 / 20

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SLIDE 21

Background suppression in Gerda

Active background suppression: by the detection of LAr scintillation light

Counts / 15 keV 1 10

2

10

3

10

4

10 yr ⋅ enriched coaxial - 23.1 kg prior active background rejection after liquid argon (LAr) veto from [EPJC 75 (2015) 9]

1/2
  • T

β β ν Monte Carlo 2 50 keV blinding Energy (keV) 1000 1500 2000 2500 3000 3500 4000 4500 5000 Counts / 15 keV 1 10

2

10

3

10

4

10 yr ⋅ enriched BEGe - 30.8 kg

GERDA 18-06 β β

Q Po

210

K

42

K

40

Tl

208

Bi

214

Bi

214

Energy (keV) 1460 1480 1500 1520 1540 Counts / 1 keV 500 K

40

Ar

40

EC K

42

Ca

42
  • β

40K/42K Compton continua

completely suppressed γ-rays survival fractions: 40K (EC) = 100 %, 42K (β−) ∼ 20 % LAr veto cut signal acceptance 97.7±1%

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 13 / 20

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SLIDE 22

Background suppression in Gerda

Active background suppression: by the detection of LAr scintillation light

Counts / 15 keV 1 10

2

10

3

10

4

10 yr ⋅ enriched coaxial - 23.1 kg prior active background rejection after liquid argon (LAr) veto from [EPJC 75 (2015) 9]

1/2
  • T

β β ν Monte Carlo 2 50 keV blinding Energy (keV) 1000 1500 2000 2500 3000 3500 4000 4500 5000 Counts / 15 keV 1 10

2

10

3

10

4

10 yr ⋅ enriched BEGe - 30.8 kg

GERDA 18-06 β β

Q Po

210

K

42

K

40

Tl

208

Bi

214

Bi

214

Energy (keV) 1460 1480 1500 1520 1540 Counts / 1 keV 500 K

40

Ar

40

EC K

42

Ca

42
  • β

40K/42K Compton continua

completely suppressed γ-rays survival fractions: 40K (EC) = 100 %, 42K (β−) ∼ 20 % LAr veto cut signal acceptance 97.7±1%

Pulse Shape Discrimination

Coaxial detectors: 2 methods Multiple site event suppression with Artificial Neural Network cut on the charge collection time for the α surface contamination Combined 0νββ acceptance: εPSD

coax = εMSE coax · εα coax = (71.2 ± 4.3)% Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 13 / 20

slide-23
SLIDE 23

Background suppression in Gerda

Active background suppression: by the detection of LAr scintillation light

Counts / 15 keV 1 10

2

10

3

10

4

10 yr ⋅ enriched coaxial - 23.1 kg prior active background rejection after liquid argon (LAr) veto from [EPJC 75 (2015) 9]

1/2
  • T

β β ν Monte Carlo 2 50 keV blinding Energy (keV) 1000 1500 2000 2500 3000 3500 4000 4500 5000 Counts / 15 keV 1 10

2

10

3

10

4

10 yr ⋅ enriched BEGe - 30.8 kg

GERDA 18-06 β β

Q Po

210

K

42

K

40

Tl

208

Bi

214

Bi

214

Energy (keV) 1460 1480 1500 1520 1540 Counts / 1 keV 500 K

40

Ar

40

EC K

42

Ca

42
  • β

40K/42K Compton continua

completely suppressed γ-rays survival fractions: 40K (EC) = 100 %, 42K (β−) ∼ 20 % LAr veto cut signal acceptance 97.7±1%

Pulse Shape Discrimination

Coaxial detectors: 2 methods Multiple site event suppression with Artificial Neural Network cut on the charge collection time for the α surface contamination Combined 0νββ acceptance: εPSD

coax = εMSE coax · εα coax = (71.2 ± 4.3)%

BEGe detectors: based on the A/E ratio high A/E: events on p+ electrode (e.g. αs from 210Po) low A/E: events on n+ electrode, multiple scattering 0νββ acceptance (228Th calibrations): εPSD

BEGe = (87.6 ± 2.5)% Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 13 / 20

slide-24
SLIDE 24

Background suppression in Gerda

Active background suppression: by the detection of LAr scintillation light

Counts / 15 keV 1 10

2

10

3

10

4

10 yr ⋅ enriched coaxial - 23.1 kg prior active background rejection after liquid argon (LAr) veto from [EPJC 75 (2015) 9]

1/2
  • T

β β ν Monte Carlo 2 50 keV blinding Energy (keV) 1000 1500 2000 2500 3000 3500 4000 4500 5000 Counts / 15 keV 1 10

2

10

3

10

4

10 yr ⋅ enriched BEGe - 30.8 kg

GERDA 18-06 β β

Q Po

210

K

42

K

40

Tl

208

Bi

214

Bi

214

Energy (keV) 1460 1480 1500 1520 1540 Counts / 1 keV 500 K

40

Ar

40

EC K

42

Ca

42
  • β

40K/42K Compton continua

completely suppressed γ-rays survival fractions: 40K (EC) = 100 %, 42K (β−) ∼ 20 % LAr veto cut signal acceptance 97.7±1%

Counts / 15 keV 1 10

2

10

3

10

4

10 yr ⋅ enriched coaxial - 23.1 kg prior active background rejection after liquid argon (LAr) veto after LAr veto and PSD from [EPJC 75 (2015) 9]

1/2
  • T

β β ν Monte Carlo 2 50 keV blinding Energy (keV) 1000 1500 2000 2500 3000 3500 4000 4500 5000 Counts / 15 keV 1 10

2

10

3

10

4

10 yr ⋅ enriched BEGe - 30.8 kg

GERDA 18-06 β β

Q Po

210

K

42

K

40

Tl

208

Bi

214

Bi

214

Energy (keV) 1460 1480 1500 1520 1540 Counts / 1 keV 500 K

42

K

40

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 13 / 20

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SLIDE 25

Gerda Phase II results

Background in Phase II: Coax: 5.7+4.1

−2.6 · 10−4 cts/(keV·kg·yr)

BEGe: 5.6+3.4

−2.4 · 10−4 cts/(keV·kg·yr)

Blinded analysis: events in Qββ ± 25 keV not processed until all analysis cuts finalized

yr ) ⋅ kg ⋅ Counts / ( keV

3 −

10

2 −

10

1 −

10

yr ⋅ enriched coaxial - 23.1 kg

GERDA 18-06

Energy (keV) 1950 2000 2050 2100 2150 yr ) ⋅ kg ⋅ Counts / ( keV

3 −

10

2 −

10

1 −

10

yr ⋅ enriched BEGe - 30.8 kg σ 2 ±

β β

Q

Phase II releases: June 2016: 10.8 kg·yr [Nature 554 (2017) 47] June 2017 +12.4 kg·yr (BEGe data) [PRL 120 (2018) 132503] June 2018 +35.7 kg·yr (BEGe and Coax data) 58.9 kg·yr exposure [Neutrino (2018)]

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 14 / 20

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SLIDE 26

Gerda Phase II results

Background in Phase II: Coax: 5.7+4.1

−2.6 · 10−4 cts/(keV·kg·yr)

BEGe: 5.6+3.4

−2.4 · 10−4 cts/(keV·kg·yr)

Blinded analysis: events in Qββ ± 25 keV not processed until all analysis cuts finalized Phase II releases: June 2016: 10.8 kg·yr [Nature 554 (2017) 47] June 2017 +12.4 kg·yr (BEGe data) [PRL 120 (2018) 132503] June 2018 +35.7 kg·yr (BEGe and Coax data) 58.9 kg·yr exposure [Neutrino (2018)] Phase I + Phase II: total exposure 82.4 kg·yr Median Sensitivity: S0ν

1/2 = 1.1 · 1026 yr (90% C.L.)

Limit on 0νββ decay: T 0ν

1/2 > 0.9 · 1026 yr (90% C.L.)

Sensitivity on the effective mass: mββ < 104 − 228 meV probability of stronger limit 63%

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 14 / 20

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SLIDE 27

After Gerda and Majorana: the Legend Experiment

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 15 / 20

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SLIDE 28

The Legend Experiment

The goal is develop a phased, 76Ge based ββ decay experimental program with discovery potential at a half-life beyond 1028 years, using existing resources as appropriate to expedite physics results

53 institutions, ∼ 250 members from Gerda and Majorana and external contributors

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 16 / 20

slide-29
SLIDE 29

The Legend Experiment [arXiv:1709.01980]

First Stage LEGEND-200

up to 200 kg of 76Ge modification of existing Gerda infrastructure at LNGS improved background, 0.6 cts/(FWHM·t·yr) start in ∼ 2021

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 17 / 20

slide-30
SLIDE 30

The Legend Experiment [arXiv:1709.01980]

First Stage LEGEND-200

up to 200 kg of 76Ge modification of existing Gerda infrastructure at LNGS improved background, 0.6 cts/(FWHM·t·yr) start in ∼ 2021

Subsequent Stage LEGEND-1000

1000 kg of 76Ge location tbd, required depth under investigation background goal < 0.1 cts/(FWHM·t·yr) timeline connected to review process

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 17 / 20

slide-31
SLIDE 31

Hardware improvements of Legend-200

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 18 / 20

slide-32
SLIDE 32

Hardware improvements of Legend-200

New Inverted Coaxial Point-Contact Ge detector first design proposed in 2011 [Cooper et al., NIMA 665 (2011)] large active mass up to 3 kg (also larger) excellent Pulse Shape Discrimination (PSD) reduced background due to smaller number of channels

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 18 / 20

slide-33
SLIDE 33

Hardware improvements of Legend-200

New Inverted Coaxial Point-Contact Ge detector first design proposed in 2011 [Cooper et al., NIMA 665 (2011)] large active mass up to 3 kg (also larger) excellent Pulse Shape Discrimination (PSD) reduced background due to smaller number of channels Low Mass Front End (LMFE) electronics reduce the signal noise w.r.t. GERDA situation experience from Majorana Demonstrator use of underground electroformed copper for nearby parts

  • ngoing test in LAr

better energy resolution + pulse shape discrimination

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 18 / 20

slide-34
SLIDE 34

Hardware improvements of Legend-200

New Inverted Coaxial Point-Contact Ge detector first design proposed in 2011 [Cooper et al., NIMA 665 (2011)] large active mass up to 3 kg (also larger) excellent Pulse Shape Discrimination (PSD) reduced background due to smaller number of channels Low Mass Front End (LMFE) electronics reduce the signal noise w.r.t. GERDA situation experience from Majorana Demonstrator use of underground electroformed copper for nearby parts

  • ngoing test in LAr

better energy resolution + pulse shape discrimination Improvement of the LAr veto take advantage of GERDA experience design studies ongoing

  • ptimization of light collection

compromise between background and cuts efficiency

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 18 / 20

slide-35
SLIDE 35

Legend: 3σ discovery sensitivity projection

3σ discovery Level to cover inverted ordering, given matrix element uncertainty

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 19 / 20

slide-36
SLIDE 36

Conclusions and Outlook

GERDA and MAJORANA reached important milestones in the 0νββ decay search: energy resolution ∼ 0.1% at Qββ lowest background ever achieved: 6 · 10−4 cts/(keV·kg·yr) exploration of the 0νββ decay at the 1026 yr scale LEGEND-200 is in preparation and will continue the search for 0νββ decay in 76Ge and reach a sensitivity of 1027 yr The experiment is fully funded Ongoing efforts to start in 2021!

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 20 / 20

slide-37
SLIDE 37

Backup Slides

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 1 / 7

slide-38
SLIDE 38

Status of 0νββ decay search

Constraints on the effective Majorana neutrino mass as function of the lightest neutrino mass mlight with GERDA 2018 and combined sensitivities as function of the sum of neutrino masses Σ with limits from cosmology as function of the effective neutrino mass mβ with the 5 yr sensitivity

  • f the KATRIN experiment

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 2 / 7

slide-39
SLIDE 39

Upgrade to Gerda Phase II [EPJC 78 (2018) 388]

30 new BEGe detectors produced and tested increase the exposure to 100 kg·yr

more active mass (35.8 kg of enrGe) longer data acquisition (∼ 3 yr)

background reduction to ∼ 10−3 /(keV·kg·yr)

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 3 / 7

slide-40
SLIDE 40

Upgrade to Gerda Phase II [EPJC 78 (2018) 388]

30 new BEGe detectors produced and tested increase the exposure to 100 kg·yr

more active mass (35.8 kg of enrGe) longer data acquisition (∼ 3 yr)

background reduction to ∼ 10−3 /(keV·kg·yr)

new low-mass holder and detector contacts

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 3 / 7

slide-41
SLIDE 41

Upgrade to Gerda Phase II [EPJC 78 (2018) 388]

30 new BEGe detectors produced and tested increase the exposure to 100 kg·yr

more active mass (35.8 kg of enrGe) longer data acquisition (∼ 3 yr)

background reduction to ∼ 10−3 /(keV·kg·yr)

new low-mass holder and detector contacts new low-activity electronics and FE contacts

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 3 / 7

slide-42
SLIDE 42

Upgrade to Gerda Phase II [EPJC 78 (2018) 388]

30 new BEGe detectors produced and tested increase the exposure to 100 kg·yr

more active mass (35.8 kg of enrGe) longer data acquisition (∼ 3 yr)

background reduction to ∼ 10−3 /(keV·kg·yr)

new low-mass holder and detector contacts new low-activity electronics and FE contacts liquid Argon readout to veto external background

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 3 / 7

slide-43
SLIDE 43

Upgrade to Gerda Phase II [EPJC 78 (2018) 388]

30 new BEGe detectors produced and tested increase the exposure to 100 kg·yr

more active mass (35.8 kg of enrGe) longer data acquisition (∼ 3 yr)

background reduction to ∼ 10−3 /(keV·kg·yr)

new low-mass holder and detector contacts new low-activity electronics and FE contacts liquid Argon readout to veto external background improved pulse shape discrimination

p

+

n

+

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 3 / 7

slide-44
SLIDE 44

Gerda data sets

data sets esposure FWHM efficiency background [kg·yr] [keV] [cts/(keV·kg·yr)] Phase I golden 17.9 4.3 (1) 0.57 (3) 11 ± 2 · 10−3 Phase I silver 1.3 4.3 (1) 0.57 (3) 30 ± 10 · 10−3 Phase I BEGe 2.4 2.7 (2) 0.66 (2) 5+4

−3 · 10−3

Phase I extra 1.9 4.2 (2) 0.57 (3) 5+4

−3 · 10−3

Phase II Coax-1 5.0 3.6 (1) 0.52 (4) 3.5+2.1

−1.5 · 10−3

Phase II Coax-2 23.1 3.6 (1) 0.48 (4) 0.6+0.4

−0.3 · 10−3

Phase II BEGe 30.8 3.0 (1) 0.60 (2) 0.6+0.4

−0.2 · 10−3

TOTAL EXPOSURE: 82.4 kg·yr the efficiency includes active volume fraction, enrichment, reconstruction

  • f 0νββ, PSD efficiency, LAr veto loss

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 4 / 7

slide-45
SLIDE 45

Gerda 0νββ decay results

Profile Likelihood Bayesian 2-side test-stat flat prior 0νββ cts best fit value T0ν

1/2 lower limit

0.9 · 1026 yr 0.8 · 1026 yr (90% CL) (90% CI) T0ν

1/2 median sensitivity

1.1 · 1026 yr 0.8 · 1026 yr (90% CL) (90% CI) Probability of stronger limit 63% 59% unbinned profile likelihood: flat background (1930-2190 keV) + Gaussian signal frequentist test-statistics and methods [EPJC 71 (2011) 1554]

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 5 / 7

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SLIDE 46

Physics Spectra

Counts / 15 keV 1 10

2

10

3

10

4

10

yr ⋅ enriched coaxial - 23.1 kg prior active background rejection 50 keV blinding

Energy (keV) 1000 1500 2000 2500 3000 3500 4000 4500 5000 Counts / 15 keV 1 10

2

10

3

10

4

10

yr ⋅ enriched BEGe - 30.8 kg

GERDA 18-06 β β

Q Po

210

K

42

K

40

Tl

208

Bi

214

Bi

214

after muon veto and detector anti-coincidence cuts peaks from 42K, 40K and Th/Ra chains α from 210Po at high energies

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 6 / 7

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SLIDE 47

Background model

Single-detector energy (keV) 1000 1500 2000 2500 3000 3500 4000 4500 5000 Counts / 10 keV

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10

4

10

GERDA 18-06

yr ⋅ enriched detectors - 60.2 kg Data Model β β ν 2 Ac

228

Tl

208

Bi +

212

Pb

214

Bi +

214

Co

60

K

40

K

42

Pa

234m

Ra

222

Po +

210

fit various sources at different locations to spectra based on screening measurements take into account events with energy in two detectors

Valerio D’Andrea (Universit` a dell’Aquila) 0νββ decay search with 76Ge Moriond 2019 - La Thuile 7 / 7

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SLIDE 48

Background model

Single-detector energy (keV) 1800 1850 1900 1950 2000 2050 2100 2150 2200 2250 Counts / 1 keV

4 −

10

3 −

10

2 −

10

1 −

10 1 10

GERDA 18-06

yr ⋅ enriched detectors - 60.2 kg Model β β ν 2 Ac

228

Tl

208

Bi +

212

Pb

214

Bi +

214

Co

60

K

40

K

42

Pa

234m

Ra

222

Po +

210

expected flat background in the ROI, main components: β from 42K α for 210Po and 222Ra γ from 212Bi and 208Tl γ from 214Bi and 214Pb

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