Assegnazioni Pd 2009 66 Ricercatori 11 Tecnologi 44.6 FTE - PowerPoint PPT Presentation

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Assegnazioni Pd 2009 66 Ricercatori 11 Tecnologi 44.6 FTE

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  1. Assegnazioni Pd 2009 66 Ricercatori 11 Tecnologi 44.6 FTE

  2. Assegnazioni Tn 2009 17 Ricercatori 9 Tecnologi 17 FTE

  3. December 30 km/s ~ 232 km/s 30 km/s June • “Classical” method”: • develop selection criteria to define a “background-free” region in the experimental parameters space • Assume a halo model (local WIMP density, velocity,..) • Calculate for each WIMP mass mc the maximum possible cross section allowed by the data Model independent signature: Earth velocity relative to halo is maximum in June, minimum in December. Modulation characteristics: Time dependence = cosine Period = 1 year Phase: maximum @ June 2nd Amplitude a few percent Only at the ‘right’ energy Hit in one crystal only

  4. 25 x 9.7 kg NaI(Tl) in a 5x5 matrix • two PMTs working in coincidence at the single ph. el. threshold • two Suprasil-B light guides directly coupled to each bare crystal • Pulse Shape recorded by Waveform Analyzer TVS641A (2 chs per detector) Roma1, Roma2, LNGS, IHEP Beijing, Jiangxi Spokesperson: R.Bernabei


  5. Shaped Cu shield surrounding light guides and PMTs Heavy shield: >10 cm of Cu, 15 cm of Pb + Cd foils, 10/40 cm Polyethylene/paraffin, about 1 m concrete (mostly outside the installation) Residual contaminants in NaI: 232T from 0.5 ppt to 7.5 ppt 238U from 0.7 to 10 ppt natK below about 20 ppb 129I/natI about 1.7*10-13 210Pb 5-30 μBq/kg Pb and Cu etching and handling in clean room. Storage underground in packed HP N2 atmosphere

  6. 67.3 keV 3.2 keV Internal 40K Tagged by an adjacent detector Internal 125I first months 40.4 keV 59.5 keV 81 keV 241Am 133Ba 30.4 keV Internal 40K: 3.2 keV due to X-rays/Auger electrons tagged by 1461 keV g in an adiacent detector Routine calibrations with 241Am • Photoelectrons/keV: from 5.5 to 7.5 • The 2 PMTs work in coincidence with hardware threshold at single p.e. • The software energy threshold is 2 keV Energy resolution Linearity

  7. PMT noise Single-hit production data g source Scintillation event 2-4 keV X2 X2 X1 X1 PMT noise Scintillation pulses 4-6 keV X2 X2 X1 X1 Noise rejection near the energy threshold From the Waveform Analyser 2048 ns time window: • The separation between noise and scintillation pulses is very good. • Very clean samples of scintillation events selected by stringent acceptance windows. • The related efficiencies evaluated by calibrations with 241Am sources of suitable activity in the same experimental conditions and energy range as the production data (efficiency measurements performed each ~10 days; typically 104–105 events per keV collected)

  8. Cumulative low-energy distribution of the single-hit scintillation events: Experimental single-hitresiduals ratevstimeandenergy: • rijk is the rate in the considered i-th time interval for the j-th detector in the k-th energy bin • flatjk is the rate of the j-th detector in the k-th energy bin averaged over the cycles. • The average is made on all the detectors (j index) and on all the energy bins (k index)

  9. DAMA/NaI (7 years) + DAMA/LIBRA (4 years)Total exposure: 300555 kgday = 0.82 tonyr Acos[w(t-t0)] ; continuous lines: t0 = 152.5 d, T = 1.00 y 2-4 keV A=(0.0215±0.0026) cpd/kg/keV 2/dof = 51.9/66 8.3  C.L. Absence of modulation? No 2/dof=117.7/67  P(A=0) = 1.310-4 2-5 keV A=(0.0176±0.0020) cpd/kg/keV 2/dof = 39.6/66 8.8  C.L. Absence of modulation? No 2/dof=116.1/67  P(A=0) = 1.910-4 2-6 keV A=(0.0129±0.0016) cpd/kg/keV 2/dof = 54.3/66 8.2  C.L. Absence of modulation? No 2/dof=116.4/67  P(A=0) = 1.810-4

  10. No modulation 6-14 keV No modulation above 90 keV Energy distribution of the modulation amplitudes, Sm, for the total exposure DE = 0.5 keV bins

  11. Summary of the results obtained in the additional investigations of possible systematics or side reactions SourceMain comment Cautious upper limit (90%C.L.) RADON Sealed Cu box in HP Nitrogen atmosphere, <2.510-6 cpd/kg/keV 3-level of sealing, etc. TEMPERATURE Installation is air conditioned+ detectors in Cu housings directly in contact <10-4 cpd/kg/keV with multi-ton shield huge heat capacity + T continuously recorded NOISE Effective full noise rejection near threshold<10-4 cpd/kg/keV ENERGY SCALE Routine + instrinsiccalibrations <1-2 10-4 cpd/kg/keV EFFICIENCIES Regularly measured by dedicated calibrations <10-4 cpd/kg/keV BACKGROUND No modulation above 6 keV; no modulation in the (2-6) keV <10-4 cpd/kg/keV multiple-hits events; this limit includes all possible sources of background SIDE REACTIONS Muon flux variation measured by MACRO<310-5 cpd/kg/keV + even if larger they cannot satisfy all the requirements of annual modulation signature Thus, they can not mimic the observed annual modulation effect

  12. DAMA/LIBRA over 4 annual cycles (0.53 ton  yr) confirms the results of DAMA/NaI (0.29 ton  yr) • The cumulative confidence level for the model independent evidence for presence of DM particle in the galactic halo is 8.2  (total exposure 0.82 ton  yr) • The measured model-independent evidence is well compatible with several candidates and interaction types (NO-VE April 2008) • Since many years the largest DM detector with high duty cycle and low • ‘electron equivalent’ threshold, KIMS (104 kg of CsI) started data taking • for annual modulation, ANAIS? • Classical WIMP scenario: comparison with other experiments depends on • many parameters, tension at high masses • Axion-like particle totally absorbed, electron recoil: KIMS?, • LXe without recoil cut?