CUPID-Mo: a world leading
limit on neutrinoless double
100
beta decay of Mo
LÉ O N A RD I M BE RT O N BE H A LF T H E CU P I D- M o CO LLA BO RATI ON

LO M O N O SOV CO N FE RE N CE
2 2 / 0 8/20 21

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Neutrinoless double beta decay2νββ◦ 2n -> 2p + 2e- + 2νe◦ even-even nucleus◦ Observed for 12 isotopes

0νββ◦ Hypothetical decay◦ 2n -> 2p + 2e◦ Peak in the sum of electrons energy spectrum◦ Lepton number violation◦ Majorana neutrino ν = ν
For light Majorana
neutrino exchange◦ Majorana neutrino needed in leptogenesis
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Scintillating bolometers◦ Crystals cool down to ~ 10-20 mK◦∆ = /◦ Detector = source◦ High detection efficiency◦ Excellent energy resolution◦ Simultaneous read out – light and heat
◦ Ge wafer operated as bolometer to measurescintillation light◦ Discrimination between β/γ and α particles

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CUPID-Mo set-up
Demonstrator for CUPID
Installed at Laboratoire Souterrain de Modane (LSM) (4800 m.w.e)
In EDELWEISS cryostat
100Mo, Q = 3034 keV
ββ20 Li2100MoO4 scintillating bolometers• ~ 0.2 kg Li2100MoO4 cylindrical crystals• ∅ 43.8 mm × 45 mm• 100Mo enrichment ~ 97 %• 2.26 kg of 100Mo• 5 towers of 4 crystals• Ge wafers as Light Detector• ∅ 44.5 mm 170 µm• SiO coating on both sides

Armengaud, E., et al. "The CUPID-Mo experiment for neutrinoless double-beta decay: performance and prospects."
The European Physical Journal C 80.1 (2020): 1-15.
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CUPID-Mo Detectors

PTFE supports

Ge wafer as Light Detector

Reflecting foils

Li2100MoO4
crystalNTD Gethermistors

NTD Gethermistors

Cu holders

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CUPID-Mo Data
Release @ Neutrino 2020
◦ Data acquired between March 2019 and June 2020
◦ The detectors were operated at 20-22 mK◦ Data release @ Neutrino2020 and published inPRL.126.181802 :◦ 2.16 kg.year exposure◦ 240 days of physic data
◦ 73 days of calibration data
◦ 6 days of 60Co data
◦ 10 days of AmBe data

Release @ TAUP 2021
◦ Exposure 2.71 kg.year◦ New analysis
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CUPID-Mo Performances
100Mo Qββ

◦ Energy Resolution◦ ΔE(FWHM) @ Qββ = 7.6 0.7 (stat.)

0.2 (syst.) keVγ(β)α 210Po◦ Light Yield◦ β/γ Light Yield per LD ~ 0.7 keV/MeV◦ > 99.9 % γ(β)/α separation

α events◦ Crystals radiopurity◦ Bulk radiopurity obtained from the counting rate in αpeaks◦ 238U/232Th and daughters ∼ (0.2 - 0.5) μBq/kg

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7◦ Blinded data analysis in 3034 keV ± 50 keV
Trigger(Optimal trigger)
CUORE Phys. Rev. Lett.
124.122501

Total efficiency aftercuts (exposureweighted average)

Amplitude from
optimal filter(maximises SNR)

Cuts
• Baseline • Multiplicity• Light Yield • Pulse Shape• Muon Veto

Thermal gainstabilization fromTh calibration data

LD Energy (cross calibrated) (keV)

CUPID-Mo Data production

Calibration with
Th/U peaks (2ndorder polynomial)

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CUPID-Mo Simulations◦ Geant 4 based program◦ Decays of the 238U and 232Th chain, or othernuclei generated in all the different components◦ We can consider 4 main regions◦ Crystal bulk and surface◦ Reflecting foils bulk and surface◦ Close sources (10 mK)◦ Cryostat and Shields◦ Detector effects convolved directly into MCspectra◦ Energy resolution and threshold◦ Cut Efficiencies◦ Anti-coincidences

Geant4 Rendering of the Edelweiss set up with the CUPID-Mo
detectors as implemented in the simulations
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9CUPID-Mo Background model◦ Global fit to the data with MC simulations◦ Bayesian approach using Just Another Gibbs Sampler◦ JAGS-based tool of analysis is developed since 2014 forbackground model studies in the framework of the CUORE
collaboration[1]◦ Simultaneous M1, M1alpha, M2sum◦ Data◦ Exposure 2.71 kg.y blinded (TAUP 2021 release)

PRELIMINARYPRELIMINARY[1] Alduino, C., et al. "Measurement of the two-neutrino double-beta decay half-life of 130Te with the CUORE-0 experiment." The European Physical Journal C 77.1 (2017): 1-18.
[1] Azzolini, O., et al. "Background model of the CUPID-0 experiment." The European Physical Journal C 79.7 (2019): 583.
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10CUPID-Mo Background budget◦ Results from the fit on blinded data
◦ Conservative Pile-up
contribution (no prior)

PRELIMINARYPRELIMINARY

ROI [3034 +/- 15] keV :Total =IMBERT LÉONARDckky
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Limit on 0νββ of 100Mo◦ Bayesian counting analysis used toextract limit◦ 3 region - one signal, two background◦ Unblinding: No events in ROI orsideband◦ One 208Tl DC event

Leads to world leading limit on0νββ of 100Mo:

T1/2 > 1.5 × 1024 y (90% CI)

mββ < (310 - 540) meV
CUPID-Mo PRL.126.181802
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New data @ TAUP2021 PRELIMINARY

222 Rn238U chain

3.8 d

α = 5490 keV◦ Exposure 2.71 kg.y
◦ Improved 0νββ analysis

212 Po218 Po

3.1 m◦ Delayed Coincidences studies(rejection of high energy beta events)◦ Improved Light Yield cuts
◦ New cuts for alpha rejection◦ New PCA cutsβ214 Biα = 6115 keV
β26.8m232Th chain◦ 2νββ and 0νββ Excited
States analysis

Qβ = 3272 keV

19.9m

214 Pbstable212 Poβ3e-7 s212 Bi61 m◦ Topological search for ES
decays using multi-site events

αα = 6207 keV

208 PbβPRELIMINARYIMBERT LÉONARD

stable208 Tl3.1 mQβ = 5001 keV13

CUPID
Next generation ton scale bolometric 0νββexperiment
To be installed at Laboratori Nazionali delGran Sasso (LNGS) in the CUORE cryostat
CUPID-Mo technology chosen for CUPID
100Mo : Q

ββ = 3034 keV

CUPID pre-CDR arXiv:1907.09376 (2019).

Li2100MoO4 scintillating crystals

0νββ sensitivity◦ Enrichment > 95 %◦ Cubic crystals : 45×45×45 mm³ -> 0.28 kg◦ ~ 1500 crystals ~ 240 kg of 100Mo◦ ΔE FWHM ~ 5 keV @ Q-value 3034 keV◦ α rejection using light signal◦ T1/2 ~ 1027 years◦ mββ ~ 12 - 20 meV
Background Index goal : 10⁻⁴ ckky
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14Conclusions
CUPID-Mo: 20 Li2100MoO4 detectors operated with simultaneous
readout of heat and light → α rejection◦ Data taking March 2019 - July 2020
◦ Has succesfully demonstrated the maturity of the technology for the next
generation experiment CUPID◦ World leading limit on 0νββ of 100Mo, with 1.21 kg·y of 100Mo :T1/2 > 1.5 × 1024 y (90% CI)◦ 4th most stringent limit mββ < (310 - 540) meV◦ New limit will be presented @ TAUP2021

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BACK-UP

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NME References◦ P. K. Rath et al., Phys. Rev. C 88, 064322 (2013).
◦ F. Simkovic, V. Rodin, A. Faessler, and P. Vogel, Phys. Rev. C 87, 045501 (2013).
◦ N. L. Vaquero, T. R. Rodriguez, and J. L. Egido, Phys. Rev. Lett. 111, 142501 (2013).
◦ J. Barea, J. Kotila, and F. Iachello, Phys. Rev. C 91, 034304 (2015).
◦ J. Hyvarinen and J. Suhonen, Phys. Rev. C 91, 024613 (2015).
◦ L. S. Song, J. M. Yao, P. Ring, and J. Meng, Phys. Rev. C 95, 024305 (2017).
◦ F. Simkovic, A. Smetana, and P. Vogel, Phys. Rev. C 98, 064325 (2018).
◦ P. K. Rath, R. Chandra, K. Chaturvedi, and P. K. Raina, Front. in Phys. 7, 64 (2019).

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Sensitivities references◦ Agostini, Matteo, Giovanni Benato, and Jason A. Detwiler. "Discovery probability of next-generation
neutrinoless double-β decay experiments." Physical Review D 96.5 (2017): 053001.
◦ Gomez-Cadenas, J. J. "Status and prospects of the NEXT experiment for neutrinoless double beta decay
searches." arXiv preprint arXiv:1906.01743 (2019).
◦ Galan, J., et al. "Topological background discrimination in the PandaX-III neutrinoless double beta decay
experiment." Journal of Physics G: Nuclear and Particle Physics 47.4 (2020): 045108.

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