Assegnazioni Pd Ricercatori 11 Tecnologi 44.6 FTE

Assegnazioni Tn Ricercatori 9 Tecnologi 17 FTE

“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 m  the maximum possible cross section allowed by the data Model independent signature: Earth velocity relative to halo is maximum in June, minimum in December. December 30 km/s ~ 232 km/s June 30 km/s Modulation characteristics: 1.Time dependence = cosine 2.Period = 1 year 3.Phase: June 2nd 4.Amplitude a few percent 5.Only at the ‘right’ energy 6.Hit in one crystal only

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

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: 232 T from 0.5 ppt to 7.5 ppt 238 U from 0.7 to 10 ppt nat K below about 20 ppb 129 I/natI about 1.7* Pb 5-30 μBq/kg Pb and Cu etching and handling in clean room. Storage underground in packed HP N 2 atmosphere Shaped Cu shield surrounding light guides and PMTs

81 keV 133 Ba Internal 40 K Tagged by an adjacent detector Internal 125 I first months 241 Am 3.2 keV 59.5 keV 67.3 keV 40.4 keV 30.4 keV Linearity Energy resolution Internal 40 K: 3.2 keV due to X-rays/Auger electrons tagged by 1461 keV g in an adiacent detector Routine calibrations with 241 Am 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

Noise rejection near the energy threshold PMT noise Scintillation event From the Waveform Analyser 2048 ns time window: 2-4 keV X2X2 X2X2 X2X2 X2X2 X1X1 X1X1 X1X1 X1X1 4-6 keV Single-hit production data  source Scintillation pulsesPMT noise 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 241 Am sources of suitable activity in the same experimental conditions and energy range as the production data (efficiency measurements performed each ~10 days; typically 10 4 –10 5 events per keV collected)

r ijk is the rate in the considered i-th time interval for the j-th detector in the k-th energy bin flat jk 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) Experimental single-hit residuals rate vs time and energy: Cumulative low-energy distribution of the single-hit scintillation events:

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

Energy distribution of the modulation amplitudes, S m, for the total exposure  E = 0.5 keV bins No modulation 6-14 keV No modulation above 90 keV

Summary of the results obtained in the additional investigations of possible systematics or side reactions SourceMain commentCautious upper limit (90%C.L.) RADON Sealed Cu box in HP Nitrogen atmosphere,<2.5  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 + instrinsic calibrations<1-2  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  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

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?