Assegnazioni Pd 200966 Ricercatori11 Tecnologi44.6 FTE

Assegnazioni Tn 200917 Ricercatori 9 Tecnologi17 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.

December30 km/s

~ 232 km/s

June

30 km/s

Modulation characteristics:1. Time dependence = cosine2. Period = 1 year3. Phase: maximum @ June 2nd4. Amplitude a few percent5. Only at the ‘right’ energy6. 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)

Glove-box forcalibration

Electronics + DAQ

Installation

Glove-box forcalibration

Electronics + DAQ

Installation

Roma1, Roma2, LNGS, IHEP Beijing,JiangxiSpokesperson: 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:232T from 0.5 ppt to 7.5 ppt238U from 0.7 to 10 pptnatK below about 20 ppb129I/natI about 1.7*10-13

210Pb 5-30 μBq/kgPb and Cu etching and handling in clean room. Storage underground in packed HP N2 atmosphere

Shaped Cu shield surrounding light guides and PMTs

81 keV

133Ba

Internal 40KTagged by an adjacent detector

Internal 125Ifirst months

241Am

3.2 keV

59.5 keV

67.3 keV

40.4 keV

30.4 keV

30.448 0.0359.1 5.1 10

( )LE

E E keV

Linearity Energy resolution

Internal 40K: 3.2 keV due to

X-rays/Auger electrons

tagged by 1461 keV 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

Noise rejection near the energy threshold

PMT noise

Scintillation event

1

2

Area (from 100 ns to 600 ns)X = ;

Area (from 0 ns to 600 ns)

Area (from 0 ns to 50 ns)X =

Area (from 0 ns to 600 ns)

From the Waveform Analyser 2048 ns time window:

2-4 keV

X2

X2 X2

X2

X1

X1 X1

X1

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 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)

•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)

jkjkijk flatr

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: 300555 kgday = 0.82 tonyr

2-5 keV

2-6 keV

A=(0.0215±0.0026) cpd/kg/keV

2/dof = 51.9/66 8.3 C.L.

2-4 keV

A=(0.0176±0.0020) cpd/kg/keV

2/dof = 39.6/66 8.8 C.L.

A=(0.0129±0.0016) cpd/kg/keV

2/dof = 54.3/66 8.2 C.L.

Absence of modulation? No

2/dof=117.7/67 P(A=0) = 1.310-4

Absence of modulation? No

2/dof=116.1/67 P(A=0) = 1.910-4

Absence of modulation? No

2/dof=116.4/67 P(A=0) = 1.810-4

Acos[(t-t0)] ; continuous lines: t0 = 152.5 d, T = 1.00 y

Energy distribution of the modulation amplitudes, Sm, for the total exposure

E = 0.5 keV bins

00 cos)( ttSStR m

No modulation 6-14 keVNo modulation above 90 keV

Summary of the results obtained in the additional Summary of the results obtained in the additional investigations of possible systematics or side investigations of possible systematics or side

reactions reactions Source Main comment Cautious upper

limit (90%C.L.)RADON Sealed Cu box in HP Nitrogen atmosphere, <2.510-6 cpd/kg/keV

3-level of sealing, etc.TEMPERATURE Installation is air conditioned+

detectors in Cu housings directly in contact <10-4 cpd/kg/keVwith 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 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 <310-5 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

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?