Direct Dark Matter and Axion Detection with CUORE

Transcription

1 Direct Dark Matter and Axion Detection with CUORE Marco Vignati University of Rome La Sapienza & INFN Rome on behalf of the CUORE collaboration Panic 11, July 5, MIT

2 988 TeO crystals Ton scale bolometric experiment for the search of neutrinoless double beta decay of 13 Te 19 towers of 5 crystals each 75 g per crystal 741 kg TeO 59 kg Te (6 kg 13 Te) 149 kg O Start data taking in 14 CUORE Laboratori Nazionali del Gran Sasso, Italy, a natural shield of 14 m of rock (equivalent vertical depth: 3 m.w.e.)

3 Bolometric technique Particle energy converted into phonons temperature variation. TeO crystals (dielectric, diamagnetic) detector = source Low crystal heat capacitance and low base temperature to see small temperature variations ΔT ~ E/C Heat bath ~ mk Weak thermal coupling Energy release Thermometer: NTD Ge thermistor R ~ MΩ Absorber Crystal TeO C ~ -9 J/K Detector response in this configuration: ~.1 mk / MeV (57 kev) ~ 5 kev FWHM 3

4 The demonstrator: Cuoricino Active mass: TeO: 4.7 Kg 13 Te: 11.3 Kg 18 Te:.5 Kg 11 modules: 4 detectors of 5x5x5 cm 3 = 79 g each modules: 9 detectors of 3x3x6 cm 3 = 33 g each enriched in 18 Te (8%) enriched in 13 Te (75%) Data taking 3-8 Installed in a dilution refrigerator: Inner shield: - 1cm Roman Pb A ( Pb) < 4 mbq/kg External Shield: - cm Pb - cm Borated polyethylene Nitrogen flushing to avoid Rn contamination. 4

5 Cuoricino limit on νdbd half-life Analyzed statistics: νdbd Half-life limit (9% C.L): Effective neutrino mass limit: Energy resolution: Rate [counts/ (1 kev)] Astropart. Phys. 34 (11) 8 6 Co γ + γ νdbd Best Fit 68% C.L. 9% C.L NME bibliography: 1 Šimkovic et al., PRC 77 (8) 4553 Civitarese et al., JoP:Conference series 173 (9) 1 3 Menéndez et al., NPA 818 (9) Barea and Iachello, PRC 79 (9) 4431

6 On the way to CUORE R&D to reduce the background in the νdbd region. Periodic CUORE crystals radioactivity/bolometric checks as they arrive from China (CUORE crystals validation runs). Construction of a CUORE-like tower. CUORE- (5 crystals, 39 kg TeO) will test the new assembly and cleaning. data taking will start this fall. 6

7 Dark matter with CUORE Dark matter searches require High mass low background good energy resolution low energy threshold The region of interest for WIMP and Axion interactions in TeO is below 5 kev The CUORICINO trigger worked on the raw samples acquired by the ADC. Energy threshold in CUORICINO ~ 3 kev too high 7

8 The optimum filter algorithm The slices of data are filtered in the frequency domain with the optimum filter algorithm, maximizing the signal to noise ratio: average signal shape (estimated from data) maximum position A.U original signal filtered signal noise power spectrum (estimated from data) sample index The continuous data flow is filtered at interlaced intervals, to ensure that the FFT convolution is always valid: time FFT window 8

9 Triggering the data ADC counts 4 3 original samples filtered samples sample index The filtered samples are less noisy than the original ones. The trigger is implemented on the filtered samples setting a threshold and a debounce time. 9

10 Pulses in the 3-6 kev range ADC counts - -4 original samples filtered samples kev signal sample index ADC counts 5 ADC counts 5 4 Electronics spikes Mechanical heating sample index sample index

11 Pulse shape discrimination To remove non-physical pulses we fit the filtered pulses with the physical pulses known shape The χ /ndf is used as shape parameter. Shape Indicator Sb X-ray 17m Te, 15m Te 11m Te m Te 19m Te 13m Te 3 11

12 Pulse shape discrimination -39 To remove non-physical pulses we fit the filtered pulses with the -4 physical pulses known shape Spike Voltage (mv) -4 The χ -4 /ndf is used as shape parameter. -43 Shape Indicator Time (s) Sb X-ray 17m Te, 15m Te 11m Te m Te 19m Te 13m Te 3 11

13 Pulse shape discrimination -39 To remove non-physical pulses we fit the filtered pulses with the -4 physical pulses known shape Spike The χ -4 /ndf is used as shape parameter. -43 Shape Indicator Sb X-ray 17m Te, 11m Te 15m Te 19m Te 11 Voltage (mv) Voltage (mv) 11m Te 13m Te Time (s) Signal Time (s)

14 Detection efficiencies Each crystal has a joule heater attached, to emulate physical pulses. Heater pulses are controlled by the DAQ, and flagged in the data. We estimated the detection efficiencies on an energy scan performed on heater pulses. Efficiency under threshold heater-data heater-mc signal-mc Efficiency above threshold: > 9 % Energy threshold: 3 kev 1 1

15 Results on a 4-crystal array 4 CUORE crystals arranged in a CUORE-like floor Operated in the Hall-C test cryostat at LNGS ~3 weeks live time 13

16 Energy spectra of the 4 crystals counts /. kev Crystal 1 counts /. kev Crystal counts /. kev Crystal 1 has the threshold at ~ kev (probably high vibration noise) On the other crystals we set a software threshold at ~5 kev. The background in the 3-5 kev region is under study counts /. kev Crystal Crystal

17 Dark matter sensitivity study The background averaged over the 3 good crystals can be projected to CUORE- and CUORE, assuming that it will be the same. Good approximation of the background below 5 kev cpd/kg/kev Assumed as CUORE background With this background we can simulate the effect of a dark matter modulation signal. Here we present a preliminary study on the sensitivity to WIMPs. 15

18 Simulation of WIMP interactions We assume that the quenching factor for nuclear recoils in TeO is 1 (A. Alessandrello et al., NIM A, vol. 49, pp ,1998). The sensitivity to a WIMP modulation signal in CUORE- (39 kg of TeO, 3 years) and in CUORE (741 kg of TeO, 5 years) is evaluated with toy MonteCarloʼs. cpd/kg/kev Subtracted spectra (simulation) (18 Apr 17 Jul) - (18 Oct 16 Jan) CUORE simulated modulation (WIMP) MW = GeV, σ = -41 cm

19 Sensitivity to CL Cross section [cm ] (normalised to nucleon) DATA listed top to bottom on plot 9% C.L. boundaries of CoGENT compatible WIMP model, shown in F CDMS II Low Threshold Ge, Spin Independent CUORE projected sensitivity (117 kg y) DAMA/LIBRA 8 3sigma, with ion channeling DAMA/LIBRA 8 3sigma, no ion channeling CUORE projected sensitivity (3.7 ton y) Edelweiss II Final Results (11) Xenon, April WIMP Mass [GeV/c ] 17

20 Axions Primakoff effect: < E < kev axio-electric effect of solar axions from 57 Fe M1: line at 14.4 kev. F=.48, D=.77, z=.56,.15 S.55 F. T. Avignone, Phys. Rev. D 79, 3515 (9). Ion Free electron Axion Atom Ongoing analysis on a test detector 18

21 Conclusions CUORE, and its precursor, CUORE- could be sensitive to Dark matter interactions Annual modulation of the counting rates in the DAMA/CoGeNT parameters space. CUORE- will start in september: Bolometric noise should be at the same level of the 4-crystal array showed in this talk. Energy threshold and detector stability will be monitored continuously. An analysis on Axions through their axio-electric interaction is under development. 19