double beta decay experiment Benjamin Schmidt for the CUPID-Mo - - PowerPoint PPT Presentation

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double beta decay experiment Benjamin Schmidt for the CUPID-Mo - - PowerPoint PPT Presentation

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TAUP 2019, Toyama - 9/11/2019 First data from the CUPID-Mo neutrinoless double beta decay experiment Benjamin Schmidt for the CUPID-Mo Collaboration The CUPID-Mo collaboration Members from China, France, Germany, Italy, Russia, Ukraine and USA

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SLIDE 1

Benjamin Schmidt for the CUPID-Mo Collaboration

TAUP 2019, Toyama - 9/11/2019

First data from the CUPID-Mo neutrinoless double beta decay experiment

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SLIDE 2
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

The CUPID-Mo collaboration

Members from China, France, Germany, Italy, Russia, Ukraine and USA

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SLIDE 3
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Reminder of the bolometric technology – CUORE

3

CUORE 750g TeO2 crystals

Copper: Thermal Bath

NTD-Ge thermistor Si heater Teflon: weak thermal link C(T) a T3 Thermal bath @ 10 mK NTD-Ge thermistor as sensor

  • Excellent energy resolution
  • Multiple isotopes can be used in

bolometric measurement

  • Ton scale cryogenic infrastructure

at LNGS

  • Background limited

ROI Reminder -Talk Neutrino#10 Tu, 16.30 New results from the CUORE experiment DE

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SLIDE 4
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

CUPID = CUORE Upgrade with Particle Identification

Idea: a | b & g particle discrimination via detection of Cherenkov or Scintillation light

  • Light yield from scintillating

compounds like Li2MoO4 is > 1 keV at Qbb

  • No prominent g line from natural

decay chains above 2614.5 keV (208Tl)

4

Other isotopes

CUORE: Experimental sensitivity with Bg No Background

208Tl 214Bi

See also arXiv:1907.09376

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SLIDE 5
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

CUPID-Mo experiment

  • Operated at LSM by the EDELWEISS/CUPID-Mo collaborations,

follow up of the LUMINEU experiment

  • 20 x ~210 g cylindrical Li2MoO4 crystals enriched to ~97% in

100Mo, dimensions: ø 44 mm x 45 mm

  • Ge wafer with SiO anti-reflective coating as light detector
  • Ge-NTD (on both Li2MoO4 and Ge light detector)
  • Cu holder (citric-acid etching for surface treatment)
  • 3M Vikutui reflectors

enhance LY to ~0.7 keV/MeV (peaked at ~600 nm)

  • First data:
  • arXiv:1909.02994 Commissioning & setup March/April 2019
  • Physics data taking since April – June 2019

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SLIDE 6
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

6

CUPID-Mo commissioning

  • 20 Li2MoO4, 19 LD, 18 Pulser lines
  • perational @ 20.7 mK
  • Median Baseline resolutions

19/20 LMO: 1.96 keV 18/19 LD: 148 eV > 99.9% alpha separation expected

  • Li2MoO4 pulse characteristics
  • 25 ms rise, 300 ms decay time (20.7 mK)
  • Ge light detector
  • 4 ms rise*, 9 ms

decay time

*limited by sampling & AC bias

  • Summed energy resolution

Li2MoO4: 5.3 keV FWHM*

(*bias from gain stabilization)

  • Good uniformity/performance

suitable for larger arrays! arXiv:1909.02994

Example LMO avg. pulse Example Heat/Light separation

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SLIDE 7
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

CUPID-Mo first data – U/Th calibration

  • Optimum Filter analysis tuned to mitigate

surplus microphonics noise

  • Data quality cuts:
  • Data quality selection on unstable

cryogenic periods

  • Basic cuts: pile up rejection and

anticoincidence cuts

  • Light Yield cut for b/g events
  • Pulse shape cut on 4 normalized shape

variables

  • Characteristic resolution @2614.5 keV

6.7 keV FWHM, H. mean 19/20 channels

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~10 days of U/Th calibration

208Tl 214Bi 214Bi 214Bi 214Bi 208Tl 228Ac 214Bi 208Tl &

e+-

214Pb

SE DE

214Bi 228Ac

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SLIDE 8
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

  • Simultaneous UEML fit (common multi-Compton ratio

& background, 19 individual resolutions)

Resolution & Energy scaling of CUPID-Mo detectors

8

  • Expected energy resolution (FWHM) at Qbb 3034 keV:

(7.7 ± 0.4) keV

  • Harm. Mean:

6.7 keV FWHM Spread (RMS): 1.9 keV

208Tl 214Bi 214Bi 214Bi

DE

228Ac 214Bi 208Tl 214Pb

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SLIDE 9
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

CUPID-Mo - First physics data

208Tl 40K 60Co 214Pb 60Co 208Tl 99Mo 214Bi 212Pb

  • Optimum Filter based Amplitude estimate

Thermal gain stabiliation on 208Tl (calibration data)

  • Data quality cuts:
  • Data quality selection on unstable

cryogenic periods (4%)

  • Basic cuts: pile up rejection and

anticoincidence cuts

  • Light Yield cut for b/g events
  • Pulse shape cuts on 4 normalized

pulse shape parameters (Risetime, Decaytime, Pulse maximum, Baseline slope)

  • Energy resolution ~ (7.8 ± 0.9) keV FWHM

@2614.5 keV, 19/20 channels

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CUPID-Mo 0.5 kg*yr

e+-

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SLIDE 10
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Energy scale and resolution (FWHM) physics data

  • Energy resolution (FWHM) at Qbb 3034 keV:

(6.6 ± 1.1) keV

  • Uncertainty and bias on energy scale from 2nd order

poynomial fit. —> DE = (0.0 ± 1.6) keV

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208Tl 40K 60Co 60Co 99Mo 208Tl 40K 60Co 99Mo 60Co 208Tl 40K 60Co 60Co 99Mo

Qbb

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SLIDE 11
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

  • Exposure: 0.5 kg*yr (~2 month)

~5 times the LUMINEU Li2MoO4 statistics

  • 100Mo with shortest T1/2 of all 2nbb isotopes: (6.90 ± 0.15 (stat.) ± 0.37 (syst.)) * 1018 yr

Spectrum dominated by 2nbb decay above ~ 500 keV (expected) (new 2nbb half-live evaluation in preparation)

CUPID-Mo – The region of interest

11

208Tl 40K 60Co 99Mo 210Po 234U/226Ra

  • Eur. Phys. J. C (2017) 77: 785

First part of physics data Summed spectrum: 0.5 kg*yr

208Tl 60Co 40K 99Mo

Light Yield cut

ROI 3034 keV

a Energy & cuts ( > 2.8 MeV ) g Energy & cuts

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SLIDE 12
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Radiopurity of Li2

100MoO4

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Uranium Thorium s = 5.2 keV

  • Minimal cuts (pile-up cut) 

> 97% signal acceptance

  • Estimate contamination in ± 15 keV window
  • 210Po (210Pb) ~ 158(3) mBq/kg
  • 190Pt 0.37(15) mBq/kg

232Th 228Th 224Ra 212Bi 238U 230Th 234Th + 226Ra 222Rn 218Po

  • degraded alphas [3,4] MeV:

0.16(2) counts/kev/kg/yr

  • No bg subtraction yet;

expect up to 2 accidental counts Contamination for both Th- and U-series are ~10 x better than assumed in CUPID preCDR (arXiv: 1907.09376) U: ~0.5 mBq/kg Th: ~0.3 mBq/kg

210Po 210Po

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SLIDE 13
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Bg for 100Mo in CUPID-Mo & beyond

13

  • Degraded alphas:
  • 0.16(2) counts/keV/kg/yr
  • Rejection by Light Yield: Detector performance compatible with > 99.9%

gaussian separation Will be further studied from data with high statistics AmBe calibration

  • Natural radioactivity - Surface & bulk:

214Bi beta (3.3 MeV Q-value) 208Tl beta (5 MeV Q-value)

  • Th chain: 232,228Th ~ 0.3 mBq/kg (bulk)
  • U chain: 238,234U, 230Th, 226Ra ~ 0.5 mBq/kg (bulk)
  • Further surface & bulk contaminations – to be studied with Geant4 MC
  • -> Background model fit
  • Random gamma pile-up (100Mo 2nbb, …)
  • r
  • NTD light detectors with Neganov-Luke amplification or TES/MMC sensors can

give >10x improvement on TR

  • Environmental muon/neutron bg

(to be studied in more detail AmBe data)

  • 7Li+n --> 8Li --> 8Be + b (16 MeV endpoint) --> a+a
  • Cosmogenic activation/ muons & muon-induced events

208Tl 2615 keV 100Mo Qbb: 3034 keV

CUPID-Mo ~ 0.5 kg*yr physics data

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SLIDE 14
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

CUPID-Mo - Outlook

  • Now: accumulated > 1 kg*yr of physics data
  • T1/2 > 3*1023 yr at 90% C.L with

~0.5 kg*yr exposure (~0.27 kg*yr of 100Mo), 81% signal acceptance

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  • Confirmed: Bolometric performance &

reproducibility, exceeded expectations for radiopurity (bulk)

  • Next: Use Geant4 MC and data to build a

detailed background model

  • Introduce data blinding
  • Optimize 0nbb analysis cuts
  • Goal: Reach > 2 kg * yr of physics

exposure, ~6 month with 19/20 detectors, 90% analysis efficiency 75% 0nbb containment

NEMO 3 limit (~ 7 kg 100Mo , 5 yr)

  • Phys. Rev. D 92(2015) 072011

T1/2 > 1.1 x 1024 yr

CUPID-Mo accumulated Analyzed – 0.5 kg*yr

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SLIDE 15
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

CUPID with 100Mo

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Goal: Discover 0nbb for effective mbb masses in the inverted hierarchy range; Explore the prospects to probe beyond arXiv:1907.09376 Details later in this session: Talk Neutrino#17 CUPID: CUORE Upgrade with Particle ID

See Talk Neutrino#17 We,18.00 CUPID: CUORE Upgrade with Particle ID

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SLIDE 16
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Thank you – Toyama/TAUP 2019

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SLIDE 17
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Backup

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SLIDE 18
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

CUPID-Mo – The Bg spectrum translated to a limit

  • Base cuts e = (97.1 ± 0.4)%

Rise + Decay time (unfiltered Pulseshape) e = (94.7 ± 0.1) % (LY + NormDelay + NormBaseline) e = (88.3 ± 0.3)%

  • Total efficiency of all cuts

e = ( 81.1 ± 0.5)%

  • Non blind analysis
  • T1/2 > 3*1023 yr at 90% C.L
  • Limit on mbb: 715 - 1190 meV

dependent on Nuclear Matrix Element

NMEs:

JHEP02 (2013) 025

  • Nucl. Phys. A 818, 139 (2009)
  • Phys. Rev. C 87, 045501 (2013)
  • Phys. Rev. C 87, 064302 (2014)
  • Phys. Rev. C 91, 034304 (2015)
  • Phys. Rev. C 91, 024613 (2015)
  • Phys. Rev. C 91, 024309 (2015)
  • Phys. Rev. C 91, 024316 (2015)
  • Phys. Rev. Lett. 105, 252503 (2010)
  • Phys. Rev. Lett. 111, 142501 (2013)

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SLIDE 19
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Evaluation of efficiencies - BaseCuts & M1

  • The alpha region - significant

210Pb/210Po contamination && no

line of sight between detectors  should all be M1 events

  • Evaluate the most basic

efficiencies on this peak

  • Efficiency of
  • SingleTrigger
  • !Filter_SuspectedPulser
  • Multiplicity1 cut
  • 1436/1479.0 counts

e = (97.1 ± 0.4)%

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SLIDE 20
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Toy studies – Lower range for an ROI Bg estimate

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  • To ensure that we don’t

get Bg from the 2vbb spectrum Laura M. and I do the following

  • Prelim Fit of 2vbb

spectrum to data

  • Calculate expected

number of events (red), expected upper limit of events at 3 and 5 C.L.

  • ROI sideband [2946 , x?]

88 keV

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SLIDE 21
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Towards estimating a Bg index

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BI calculation ToDo: Exclude 0vbb region

  • 2 month of good data ~ 0.51 kg*yr
  • DS8037+DS8038

(processed up to Energy Coincidences, Shape)

  • Bg index from [2946, x]

0 counts in window + require Bg model

30 keV signal ROI

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SLIDE 22
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Backup - CUORE background budget (TeO2)

22

  • C. Alduino, et al. Eur. Phys. J. C 77, 543 (2017)

CUORE goal CUPID goal degraded a background

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SLIDE 23
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

  • Minimal cuts (pile-up, !isPulser,

absolute RiseTime)

  • 210Po: 158(3) mBq/kg

190Pt: 0.37(15) mBq/kg

Degraded alphas 0.16(2) ckky No Bg subtraction ~2 counts in 30 keV

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Thorium chain Activity (mBq/kg) Energy (+- 15 keV)

232Th

0.31 (0.14) 4082

228Th

0.37 (0.15) 5520

224Ra

0.25 (0.12) 5789

212Bi - a 36%

branching - feeds 208Tl 0.12 (0.09) a only —> 0.34 (0.24) 6207

Alpha region - 15 keV window

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SLIDE 24
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Alpha region - 15 keV window

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Uranium chain Activity mBq/kg Energy (keV)

238U

0.50 (0.18) 4270

230Th

0.31 (0.14) 4770

226Ra + 234U

1.4 (0.3) —>4864 4857.5/4871

222Rn

0.62 (0.20) 5590

218Po

0.50 (0.17) 6115

Notes on 222Rn: The daughter half live of 218Po is 3.098 minutes  Expect that < 1% of the 218Po decays happen in the first 2 s after the 222Rn decay (and both will be removed as pile-up by cuts) Negligible compared to correction from degraded alphas

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SLIDE 25
  • B. Schmidt

Toyama, TAUP 2019 - 09/11/2019

Example of normalized shape parameters (AmBe)

NormDelay NormBaseline NormRise NormDecay All Norm variables have been defined on the Gamma distribution in the AmBe data.  no major extrapolation uncertainty in the shape normalization LMO 19 LMO 19 LMO 19 LMO 19

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