The start up of the CUORE experiment at LNGS CUORE Photo credit: - PowerPoint PPT Presentation

The start up of the CUORE experiment at LNGS CUORE Photo credit: Yury Suvorov Antonio Branca @ INFN Padova On behalf of the CUORE Collaboration WIN2017 @ UC Irvine – 19-24 June 2017

Double beta decay (DBD) CUORE ( A , Z ) → ( A , Z + 2) + 2 e − + 2 ν 2ν DBD: 0ν DBD: ( A , Z ) → ( A , Z + 2) + 2 e − - proposed in 1935 by - proposed in 1937 by Maria Goeppert-Mayer; EKore Majorana; - 2 nd order process allowed - requires physics beyond in the Standard Model; Standard Model; τ ~10 19 − 21 yr τ > 10 24 − 25 yr Energy spectrum of the two electrons in DBD 0ν DBD Signature: monochromaOc line in the energy spectrum at the energy value smeared by detector resoluOon! 19-24 June 2017 A. Branca - WIN2017 @ UCI 2

Double beta decay (DBD) II CUORE EffecOve Majorana mass m ββ = f ( Δ m 1,2 , Δ m 2,3 , m 1 , α 1 , α 2 , δ ) The 0ν DBD half-life: 1 / 2 ) � 1 = G 0 ν ( Q, Z ) | M 0 ν | 2 | h m ββ i | 2 ( T 0 ν m 2 e Phase space Nuclear Matrix Element factor ~Q 5 (theoreOcal uncertainty ~2-3) ßß (accurately calculable) ISM 9 | IBM ν 0 QRPA-T |M Physics consequences if 0ν DBD is observed: 8 QRPA-J PHFB 7 GCM 6 • proof of the Majorana nature of neutrino; 5 • constrain on the neutrino mass hierarchy and scale; 4 3 • lepton number violaOon (ΔL = 2): a possible source 2 of maKer-anOmaKer asymmetry in the universe; 1 0 48 76 82 96 100 116 128 130 130 150 124 Ca Ge Se Zr Mo Cd Sn Te Te Xe Nd 19-24 June 2017 A. Branca - WIN2017 @ UCI 3

Sensitivity CUORE Half-life corresponding to the minimum number of detectable signal events above background at a given C.L. Detector mass Isotopic abundance Measuring Ome sens . ∝ i . a . ⋅ ε ⋅ M ⋅ t (also “live Ome”) ( ) 0 ν T 1/2 Δ E ⋅ B Background Detector efficiency Energy resoluOon In order to build a high sensiOvity experiment: • select 0v DBD candidates with high natural isotopic abundance or enriched; • high detector mass; • good detector stability over a long period; • extremely high energy resoluOon; • extremely low background environment; 19-24 June 2017 A. Branca - WIN2017 @ UCI 4

Bolometric technique in CUORE CUORE (A) Copper frame: 10 mK heat sink A (B) PTFE holders: weak thermal coupling D (D) Si joule heater: C reference pulses (C) TeO 2 crystal: energy absorber B E RadiaEon: (E) NTD Ge thermistor: energy deposit 3200 resisOve thermometer Amplitude [mV] E 3000 Δ T = Bolometer: detector and source C ( T ) 2800 of 0ν DBD. High efficiency and readout 2600 Δ T 3 ⎛ ⎞ resoluOon; T 2400 C ( T ) = ⎜ ⎟ ϑ D ⎝ ⎠ 2200 Low temperature needed: 2000 C ~10 − 9 J Δ T = 0.1 mK 1800 @ T = 10 mK ⇒ K ; MeV ; τ ~1 s ; 1600 0 0.5 1 1.5 2 2.5 3 3.5 4 Time [s] 19-24 June 2017 A. Branca - WIN2017 @ UCI 5

A rare event search CUORE Searching for a rare event (0ν DBD): ……………………… τ > 10 24 − 25 yr Extremely important to reduce as much as possible backgrounds: a. natural radioacOvity from outside the detector: cosmic ray muons induced background; • neutron and gamma fluxes; • b. natural radioacOvity from the detector itself: long-lived nuclei ( 40 K, 238 U, 232 Th); • anthropogenic radioacOve isotopes ( 60 Co, • 137 Cs, 134 Cs); cosmogenical radioacOve isotopes ( 60 Co); • c. mechanical vibraOon noise: cryogenic system and seismic noise; • 19-24 June 2017 A. Branca - WIN2017 @ UCI 6

CUORE installed @ LNGS CUORE CUORE @ Hall A • average depth: ~3600 m.w.e. • muon flux: ~3×10 -8 μ/(s cm 2 ) • neutron flux: < 4×10 -6 n/(s cm 2 ) • gamma flux: ~0.73 γ/(s cm 2 ) 19-24 June 2017 A. Branca - WIN2017 @ UCI 7

Suspension System CUORE Abatement of vibrations: detector mechanical Y-Beam decoupling from the outside environment: Minus-K • detector hung by the Y-Beam through cables made of stainless steel tie bars, Kevlar ropes and copper bars (damping the MSP horizontal oscillations); • 3 minus-K springs connect the Y-Beam to the Main Support Plate, MSP (attenuating Lead shield the noise of ~35 dB); • elastometers at the structure basis (seismic H 3 BO 3 isolators); panels Radioactive background reduction: Polyethylene • outer neutron shield: polyethylene + borated powder; • outer gamma shield: lead shield; Elastometers 19-24 June 2017 A. Branca - WIN2017 @ UCI 8

Cryogenic System CUORE Specifics: • Fast Cooling System: T down to ~40 K; • 5 Pulse Tubes cryocooler: T down to ~4 K; • Dilution Refrigerator: T operations 10 mK; • Nominal cooling power: 3 µW @ 10 mK; • Cryogen-free cryostat: high duty cycle; Cool down ~15 tons @ T < 4 K and ~1.5 tons @ T = 10 mK in a few weeks. Radioactive background reduction: • material screening and accurate selection to ensure radiopurity; • lead shielding (Roman and modern Pb); 19-24 June 2017 A. Branca - WIN2017 @ UCI 9

The CUORE “core” CUORE 988 TeO 2 crystals arranged in 19 towers (13 floors - 52 crystals each): 130 Te for 0v DBD: good Q-value • (2528 keV) in low β/γ region, high natural abundance (34.17%); • total TeO 2 mass of 742 kg (206 kg of 130 Te); RadioacOve background reducOon: • minimizaOon of material/ surface facing the crystals; • developed a stringent protocol for the tower assembly and All 19 towers installed material cleaning (tested on between July-August 2016 predecessor CUORE-0 ); A single CUORE tower 19-24 June 2017 A. Branca - WIN2017 @ UCI 10

CUORE0: the first CUORE tower CUORE First detector tower built using the new techniques and assembly line developed for CUORE: • operated from 2013 to 2015 in old Cuoricino cryostat; • proof of concept for CUORE; • 0ν DBD search by itself; 6 4 ) Residual ( σ ) σ 4 2 Residual ( 2 0 0 − 2 –2 4 − –4 − 6 18 2560 2570 2580 2590 2600 2610 2620 2630 2640 2650 0.25 Summed calibration data 208 Tl γ χ 2 /NDF = 43.9/46 Event Rate (counts/(keV kg yr)) 16 Projected fit 4 10 14 0.2 Events / (2 keV) Counts / (0.5 keV) 12 Te X-ray 3 0.15 10 10 escapes 8 0.1 2 6 10 4 0.05 2 10 0 0 2470 2480 2490 2500 2510 2520 2530 2540 2550 2560 2570 1 Reconstructed Energy (keV) RESULTS: 2560 2570 2580 2590 2600 2610 2620 2630 2640 2650 Reconstructed Energy (keV) Ø 0νββ upper limit: T 1/2 (0ν) > 4×10 24 yr (@ 90% C.L.) combined CUORE0 + Cuoricino results; ü ROI background: 0.058 ± 0.004 c/(keV Ÿ kg Ÿ yr); ü ResoluOon: 5.1 ± 0.3 keV FWHM @ 2615 keV; ResoluOon consistent with the CUORE goal of 5 keV. 19-24 June 2017 A. Branca - WIN2017 @ UCI 11

Material cleaning and assembling CUORE Production of the TeO 2 crystals: • by Shanghai Institute of Ceramics, Chinese Academy of Science (SICCAS); • two successive crystal growths starting from high purity synthetized TeO 2 powder; • cutting, orienting and shaping from raw ingots and surface polishing and packaging; • all operations performed in a dedicated clean room and following strict controls to limit radioactive contamination; Cleaning of copper surfaces (tower parts and 10 mK cryostat shield): • new cleaning techniques developed at LNL; • tumbling, electropolishing, chemical etching, magnetron plasma aimed at the removal of a thin layer of material (from 1 µm to 100 µm); 19-24 June 2017 A. Branca - WIN2017 @ UCI 12

Material cleaning and assembling CUORE Strict protocol adopted for each step of the CUORE towers construction: all in N 2 atmosphere and within glove boxes to avoid radioactive recontamination; 2. tower assembly 1. sensors gluing 3. wire bonding 4. tower storage 19-24 June 2017 A. Branca - WIN2017 @ UCI 13

Background reduction effectiveness CUORE β/γ dominated α dominated 210 Po 208 Tl 190 Pt 234 U/ 226 Ra/ 230 Th Comparison of 222 Rn 238 U 218 Po the background in Cuoricino and CUORE-0 • Material cleaning: 238 U and 232 Th α Background indexes (counts/(keV•kg•yr)) lines reduced (~ factor of 7); 0ν DBD region α region • Tower assembly in N 2 atmosphere: (2.47-2.58 MeV) (2.7-3.9 MeV) 238 U γ lines reduced (~ factor 2/3); Cuoricino 0.169 ± 0.006 0.110 ± 0.001 • Same Cuoricino cryostat: 232 Th γ lines CUORE-0 0.058 ± 0.004 0.016 ± 0.001 not reduced; 19-24 June 2017 A. Branca - WIN2017 @ UCI 14

CUORE background projection CUORE Main background index in the 0ν DBD region expected for the various components of CUORE Measured in Preliminary CUORE-0 Material expected screening dominant contribuOon from the Cu of the towers structure LNGS Fluxes Projected total BI in the 0ν DBD region is consistent with CUORE background goal (10 -2 counts/(keV•kg•yr)): counts + 0.23 ( syst .)) ⋅ 10 − 2 BI = (1.02 ± 0.03( stat .) − 0.10 (Preliminary) kev ⋅ kg ⋅ yr 19-24 June 2017 A. Branca - WIN2017 @ UCI 15

Cryostat commissioning CUORE Commissioning completed in March 2016: 300 K • stable base T = 6.3 mK over 70 days (no 40 K detector, full load); • full detector read-out chain (electronics, DAQ) 4 K test, temperature stability with Mini-Tower (8 crystal tower); 600 mK 50 mK 10 mK Mini-Tower resoluOon without noise opOmizaOon. 19-24 June 2017 A. Branca - WIN2017 @ UCI 16

CUORE Installation CUORE 10 mK Cu shield closed Towers installaOon completed Lead shield installed Aug 2016 Cryostat closed Cables rouOng Sep – Nov 2016 Nov 2016 19-24 June 2017 A. Branca - WIN2017 @ UCI 17