GERDA: First Results from GERDA II and Perspec:ves

Transcription

1 GERDA: First Results from GERDA II and Perspec:ves C.M. Ca?adori CSNII - 21 Luglio 2016 Located in Hall LNGS

2 GERDA crono- history 2004: Proposal 2005: Funding (MPI, BMBF, INFN, in- kind contribu:ons from ITEP,INR,JINR) : Infrastructures/structures construc:on (WT,Cryostat, Building, Clean room) : GERDA I Commissioning 42Ar problem faced and successfully mi:gated : GERDA I data taking : Setup upgrade to Phase II December 2015: GERDA II Physics data taking started

3 The GERDA Collaboration Outline

4 GERDA Setup

5 The GERDA setup GERDA I detectors 21/07/2016 C.M.Ca?adori CSNII 5

6 BEGe inserdon GERDA I: Nov June νββ T 1/2 pubblished (5.01 kg y) Goals Scru:nize ββ claim Demonstrate BI: 10-2 cts/(kky) Exposure: 21.6 kg y à Q ββ = 4.8 kev Detectors: - 6 (of 8) enr Ge COAX - 4(of 5) enr BEGe- type Ge - 1 nat Ge COAX (not in ββ data- set) à Q ββ = 3.2 kev Achieved BI (evaluated in 230 kev around Q bb ) : - COAX: BI: (18 ± 2) 10-3 cts/(kky) BI: (11 ± 2) 10-3 cts/(kky) w. PSD - BEGe BI: cts/(kky) BI: cts/(kky) w. PSD

7 GERDA I: T 1/2 0ν Performed Profile Likelihood fit of the 3 data sets B+S: described by constant term + Gaus(Q ββ,σ E ) 4 free parameters in the fit B gold, B silv,b BEGe,1/ T 1/2 0ν Systema:cs folded in PSD NO PSD PRL111(2013) FrequenDst approach Best fit: N 0ν = 0 N 0ν < % C.L. T 1/2 0ν > 2.1 x % CL Median sensi:vity: T 1/2 0ν > 2.4 x yr Bayesian approach Flat prior for 1 / T 1/2 0ν Best fit: N 0ν = 0 T 1/2 0ν > 1.9 x % CI Median sensi:vity: T 1/2 0ν > 2.1 x yr

8 GERDA I vs 0νββ observa:on claim PLB 586(2004) For T 0ν 1/2 = 1.19 x yr Expected Signal (aler PSD): 5.9 ± 1.4 cts in ±2σ Expected Bckgd (aler PSD): 2.0 ± 0.3 cts in ±2σ Observed: 3.0 (0 in ±1σ) PSD NO PSD From profile likelihood Assuming H1 trueà P (N 0ν =0 )=1% Comparing H1: Claimed signal H0: Background only Bayes factor P(H1)/P(H0)=0.024 (uncertain:es on claim included) Claim poorly credible

9 GERDA II: Setup Upgrade 30 enr BEGe (20 kg) detectors produced at Canberra. 5 units already deployed in GERDA I [EPJC 75 (2015) 39] New lower mass holders Spring loaded contacts changed to wire bonded to improve contact quality New low- mass low- ac:vity FE electronics and detector- to- FE contacts

10 GERDA II: Setup Upgrade 21/07/2016 C.M.Ca?adori CSNII

11 GERDA II: Final configura:on All Working Few show reverse current azer months of operadon in LAr. Some detectors show instabilides- > not used for analysis

12 GERDA II: Data taking 131 live days: 25 th Dec 2015 to 1 st Jun % duty factor Blinding applied at Q ββ ± 25 kev Usable for analysis 10.8 kg yr ü 5.8 kg yr BEGe (~81% of enr BEGe mass) ü 5.0 kg yr coax (~77% of enr coax mass) plus ü 2.8 kg yr nat Ge (for background studies) About 0.4 kg yr of BEGe data not considered due to poor PSD Addi:onal unpublished data from Phase I (1.9 kg yr) Taken aler the freezing of the Phase I release dataset (Jul- Sep 2013) Never unblinded since 2013

13 GERDA II: Energy Scale & Resolu:on FWHM [kev] String 1 String 2 String 3 String 4 String 5 String 6 String 7 BEGe enrcoax natcoax detector number

14 Energy Resolu:on in PHY- DATA enr BEGE: FWHM= 2.66 ± 0.06 enr coax: FWHM= 3.1 ± 0.12 Good Energy ResoluDon ß à Stability of the Calibrated Energy Scale LAr veto not applyed

15 α structures α contamina:on larger for coax than for BEGEs observed to decay with half- life compa:ble with 210 Po + a slowest component PSD cut completely the α events α events rate observed to decay with half- life compa:ble with 210 Po + a slower component PSD cut completely the α events Cumula:ve (BEGe & coax) α event :me distribu:on

16 Background modeling - 1 Coax p- value: 0.3 BEGe p- value: 0.6 Same approach as in Phase I EPJ. C 74 (2014) 2764 Mostly, same components considered Fit range kev Results for 228 Th and 226 Ra consistent with screening results T 1/2 of 2ν2β decay (1.84±0.05 stat ) yr for coax (2.00±0.05 stat ) yr for BEGe Consistent with the Phase I value (1.93±0.09) yr C.M.Ca?adori CSNII 16 [Eur. Phys. J. C 75 (2015) 416]

17 Background in ROI Background in the ROI (before LAr and PSD) α from 210 Po and 222 Rn daughters β from 42 K γ from 214 Bi and 208 Tl Flat background expected at Q ββ Use the same analysis window as Phase I kev, excl. ±5 kev around two known γ lines UniCampinas, 21 Jul

18 Pulse Shape Discrimina:on (PSD) to discriminate ββ- like (SSE) to γ- like (MSE) events Different weigh:ng poten:als for Coax and BEGe COAX: Ar:ficial Neural Network (ANN) es:mator or TMVA of pulse profile used as PSD parameter Simulated pulses EPJC 73(2013) 2583 Simulated pulses BEGe: Amplitude of Current/Amplitude of Charge Pulse (A/E) is the PSD parameter

19 PSD for BEGe detectors Eur. Phys. J. C 73 (2013) 2583 Event- per- event selec:on Above band: events on p+ electrode (e.g. α's from 210 Po) Below band: events on n+ electrode, mul:ple sca?ering Acceptance for 0ν2β events: (87.3 ± 0.9)% Es:mated from 208 Tl DEP Double- check at low energy with 2νββ events (LAr cut) 0ν2β accepted Mul:- site events Degraded α C.M.Ca?adori CSNII 19

20 PSD for coaxials PSD for coax detectors less effec:ve than for BEGes Ar:ficial neural network (ANN), as in Phase I Trained on signal (SSE) : 208 Tl (2614 kev) DEP at 1592 kev Background (MSE): kev γ- line Acceptance for 0ν2β events: (80±9)% (preliminary!!) Double check with Compton edge and 2ν2β New ingredient: dedicated ANN for α Test/train sample from data Acceptance for 0ν2β events: (96±1)% Combined acceptance (77±9)% [Eur. Phys. J. C 73 (2013) 2583] current pulses for SSE C.M.Ca?adori CSNII 20

21 LAr performance with physics data LAr readout only when there is a trigger in Ge Dead Dme 2.3% γ- rays Survival Frac:ons (SF): 40 K (EC) : 100% 42 K (β- decay): ~20% 42 K (β - ) β in LAr 40 K (EC) no energy in LAr Only 2νββ lel T 1/2 (2νββ) fixed as yr (Phase I) SF in E range MeV: (70.4 ± 0.3)% 40 K and 42 K con:nua completely suppressed C.M.Ca?adori CSNII 21

22 GERDA II: Unblinded BEGE 5.8 kg y counts / 20 kev Q ββ BEGe (5.8 kg yr) raw spectrum AC + MV AC + MV + LAr AC + MV + LAr + PSD energy [kev]

23 GERDA II: Unblinded BEGe 5.8 kg y counts / 20 kev Q ββ BEGe (5.8 kg yr) raw spectrum AC + MV AC + MV + LAr AC + MV + LAr + PSD energy [kev] counts / kev BI raw = 23 cts - - > cts/(kky) BI LAr = 6 cts - - > cts/(kky) BI PSD = 1 cts - - > cts/(kky) Q ββ 240 kev ne-o range raw spectrum AC + MV AC + MV + LAr AC + MV + LAr + PSD energy [kev] counts / kev Q ββ raw spectrum AC + MV AC + MV + LAr AC + MV + LAr + PSD energy [kev]

24 GERDA II: Unblinded COAX 5.0 kg y counts / 20 kev Q ββ Coax (5.0 kg yr) raw spectrum AC + MV AC + MV + LAr AC + MV + LAr + PSD energy [kev]

25 GERDA II: Unblinded COAX 5.0 kg y counts / 20 kev Q ββ Coax (5.0 kg yr) raw spectrum AC + MV AC + MV + LAr AC + MV + LAr + PSD energy [kev] counts / kev BI raw = 19 cts - - > cts/kky BI LAr = 12 cts - - > cts/kky BI PSD = 4 cts - - > cts/kky Q ββ 240 kev ne-o range raw spectrum AC + MV AC + MV + LAr AC + MV + LAr + PSD energy [kev] counts / kev Q ββ raw spectrum AC + MV AC + MV + LAr AC + MV + LAr + PSD energy [kev]

26 Event counts BEGe (5.8 kg yr) Coax (5.0 kg yr) Before unblinding kev (190 kev) 1 3 Expected aler unblinding Q ββ ±25 kev Expected aler unblinding kev, excl. Q ββ (230 kev) Observed aler unblinding Q ββ ±25 kev 0 1 Observed aler unblinding kev, excl. Q ββ (240 kev) 1 4 Background (counts/kev kg yr) kev 10 Feb :04 Coax kev 13 Mar :42 Coax kev 13 Mar :40 BEGe kev 28 Mar :00 Coax kev 22 May :44 Coax Closest event to Q ββ (21 kev away!) No event within ± 3σ from Q ββ UniCampinas, 21 Jul

27 GERDA I & II: Unblinded data, ε, BI, FWHM

28 GERDA: T 1/2 0ν

29 GERDA II: Results

30 Comparison of Ge vs Xe & Te projects Achieved in blue Gerda II Gerda II GERDA I Total Mass of isotope [kg] Expected/ Achieved BI [cts/kev kg y] 10-3 <=10-3 ~10-2 Expected/ Achieved FWHM [kev] < Expo sure [kg y] ~ T 1/2 SensiDvity (90%CL) [y] > Majorana 30 <10-3 < 4 > Cuore Cuore 0 Cuoricino n- EXO EXO 200 ult. EXO 200 KZ uldmate KZ comb. Kam- Zen II Kam- Zen II Kam- Zen I m ee SensiDvity (90%CL) [mev] down to

31 10-12 years ago: The 0νββ observa:on claim

32 INFN Contribu:ons to GERDA Project LNGS Lab!!!! Costruzione WT (MiB e LNGS) Analisi di rischio ed autorizzazioni (MiB e LNGS) Misure screening ICPMS e γ- screening (LNGS e MiB) Responsabilita FE (GERDA I e GERDAII) (MiB): Proge?o FE (GERDA I e II): MI, MiB Produzione in v.la, tests ed integrazione con detectors: MiB e MI Cablaggi custom (HV e Segnale) criogenici e v.la (MiB) Passan: e filtri HV (HV in gas Ar!!!), HV PS (messa a punto con CAEN), LVPS (MiB e PD) Slow Control (GERDA I & II - PD) R&D e misure cara?erizzazione rivelatori depl BEGe (LNGS,MiB,PD) Produzione Bench- tests e Co- Coordinamento Tests acce?azione Canberra (in vuoto) post- produzione rivelatori BEGe c/o HADES Underground Lab(A. Garfagnini - PD) Contributo R&D/Contact Team Canberra e gara INFN BEGe arricchi: (C. Ca?adori- MiB) Analisi: Coordinatore Sviluppo tool analisi e MC (L.Pandola- LNGS/LNS) Analysis Coordinator (L.Pandola- LNGS/LNS) Data flow & quality (M. Agos:ni GSSI/LNGS) Data Taking: Run Coordinator (F. Salamida- MiB) Ges:one ed SW Analisi Calibrazioni (MiB e LNGS) Mantenimento apparato in misura Posizioni Management: R. Brugnera (Chair CB da 2015) C. Ca?adori (Deputy Spokeperson un:ll 2014)

33 What Next GERDA? Due tecnologie disponibili a la GERDA a la Majorana Mee:ng GERDA- Majorana si sono tenu: in ques: anni con cadenza annuale in vista di un proge?o comune La scelta dipende dalle performances e dal Background Index raggiun: Dimensione proge: 200 kg (38 kg GERDA + 30 kg Majorana + new enr Ge (in form of BEGe). Costs: ~30 ML. Already presented at LNGS 1 ton project non fabile nelle presen: stru?ure GERDA Loca:on: LNGS/USA/Canada/Cina

34 What Next GERDA II? Gruppi avi per LoI New 76 Ge project: Tu I Gruppi Majorana, molto insisten: per interce?are finanziamen: DOE e NSF Gruppi GERDA: MPP,TUM,MPIK Gruppi Cinesi (Proposal di 1 ton experiment a China JinPing Laboratory (CJPL) Aprile a Monaco, Open Mee:ng su 1 ton 76 Ge experiment E gli italiani? Accumulato grande know- how su aspe chiave- > coinvolgimento in 200 kg project? Grande Problema di risorse umane Per ora posizione a?endista, anche in vista di altri risulta: sperimentali su gerarchia neutrini, neutrini sterili etc. Proposta (mia): mee:ng dedicato con management INFN

35 EXTRA Slides

36 GERDA I: Unblinded data PRL111(2013) In 230 ββ In ROI ± 5 kev Expected bckgd only PSD 4.5% 5.1 PSD 2.5% 7.1% % Bckgrd Rej Coax PSD ~ 43% Bckgrd Rej BEGe PSD ~ 87%