DAMA experiment: DAMA experiment: status and reports. Second International Summer Student. School on Neutrino Physics in Memory of

Transcription

1 DAMA experiment: DAMA experiment: status and reports R. Bernabei Univ. Roma - Tor Vergata and INFN-Roma2 Second International Summer Student School on Neutrino Physics in Memory of Bruno Pontecorvo September 2003

2 low bckg Ge for sampling meas. NaI(Tl) LIBRA LXe R&D

3 Proposal by R. Bernabei, P.Belli, C. Bacci, A. Incicchitti, R. Marcovaldi and D. Prosperi on large mass NaI(Tl) and liquid Xenon experiments for Dark Matter search and first funding on The chinese colleagues joined the project in 1992 Several results since the beginning and various test/preliminary set-ups the ~ 100 kg NaI(Tl) set-up: -First experimental result published on 1996 (DAMA coll., PLB389(1996)757). - First result on WIMP annual modulation signature presented at TAUP97 - Data from 4 annual cycles released and published - Several other rare processes investigated. - New electronics and DAQ in summer Out of operation in July July 2003: release of the cumulative 7 annual cycles exposure

4 P. Belli, R.Bernabei, A. Bussolotti*, F. Cappella, R. Cerulli +, P. Delfini*, F. Montecchia %, F. Nozzoli Dip. di Fisica, Universita' di Roma ''Tor Vergata and INFN, sez. Roma2, I Rome, Italy A. Incicchitti, A. Mattei *, D. Prosperi Dip. di Fisica, Universita' di Roma ''La Sapienza and INFN, sez. Roma, I Rome, Italy Past members who gave very valuable contributions: M. Amato, C. Bacci, V. Bidoli*, F. Bronzini*, D.B. Chen, L.K. Ding, W. Di Nicolantonio, H.L. He, G. Ignesti, V. Landoni, G. Ranelli*, X.D. Sheng, G.X. Sun and Z.G. Yao + in the neutron measurements at ENEA-Frascati: M. Angelone, P. Batistoni and M. Pillon underlined the coll. leader * technical staff + now: INFN-LNGS, Assergi (Aq), Italy % also: Universita' "Campus Biomedico" di Roma, 00155, Rome, Italy $ also: University of Zhao Qing, Guang Dong, China C.J. Dai, H.H. Kuang, J.M. Ma, Z.P. Ye $ IHEP, Chinese Academy, P.O. Box 918/3, Beijing , China

5 The dynamical evolution of the Universe depends on the quantity and kind of mass and energy densities present. The curvature radius of the Universe is related to the density parameter Ω = ρ/ρ c (ρ = present density of mass and energy in the Universe and ρ c = 3H 02 /8πG). W is a key parameter. The Milky Way

6 70 years later than the first evidence for Dark Matter by Zwicky

7 The WIMPs relic CDM particles from primordial Universe an heavy ν of the 4-th family the sneutrino in the Smith and Weiner scenario even a particle not yet foreseen by theories In thermal equilibrium in the early stage of Universe Non relativistic at decoupling time <s ann. v> ~ /W WIMP h 2 cm 3 s -1 fi s ordinary matter ~ s weak Expected flux: F ~ (GeV/M W ) cm -2 s -1 (0.2<r halo <0.7 GeV cm -3 ) Form a dissipationless gas trapped in the gravitational field of the Galaxy (v ~10-3 c) Searching for a candidate neutral stable (or with τ ~ age of Universe) massive SUSY R-parity conserved LSP is stable LSP (neutralino, sneutrino, gravitino, axino)

8 Investigating the presence of a WIMP component in the galactic halo by the model independent WIMP annual modulation signature km/s Sun Drukier,Freese,Spergel PRD86 Freese et al. PRD88 30 km/s Earth S k [η(t)] = v sun = 232 km/s (Sun velocity in the halo) v orb = 30 km/s (Earth velocity around the Sun) γ = π/3 ω = 2π/T T = 1 year t 0 = 2 nd June (when v is maximum) v (t) = v sun + v orb cosγcos[ω(t-t 0 )] dr de R S 0,k + S m,k cos[ω (t t 0 )] de R Expected rate in given energy bin changes because the annual motion of the Earth around the Sun moving in the Galaxy Ek Requirements of the annual modulation 1) Modulated rate according cosine 2) In a definite low energy range 3) With a proper period (1 year) 4) With proper phase (about 2 June) 5) For single hit in a multi-detector set-up 6) With modulated amplitude in the region of maximal sensitivity ~ < 7% (larger for WIMP with preferred inelastic interaction, PRD64 (2001)043502) To mimic this signature, spurious effects and side reactions must t (not only - obviously - be able to account for the whole observed modulation amplitude, but also) satisfy contemporaneously c all these 6 requirements

9 NaI(Tl) well suitable to investigate the WIMP annual modulation signature Well known technology Large mass possible Technology for radiopurification feasible Full control of running conditions feasible High duty cycle Cost/Mass relatively low Sensitive to purely SI, purely SD and mixed SI&SD coupled WIMP + preferred sensitivity in several scenarios (+ Statistical discrimination of recoil nuclei feasible in suitable conditions at reasonable level )

10 ~100 kg NaI(Tl Tl) ) DAMA set-up: data taking completed on July 2002 Performances: N.Cim.A112(1999)545 + new electronics and DAQ since summer 2000: Riv. N. Cim. 26 (2003) 1-73 Results on rare processes: Possible Pauli exclusion principle violation PLB408(1997)439 Nuclear level excitation of 127 I and 23 Na during CNC processes PRC60(1999) Electron stability and non-paulian transitions in Iodine atoms (by L-shell) PLB460(1999)235 Exotic Dark Matter search PRL83(1999)4918 Search for solar axions by Primakoff effect in NaI(Tl) crystals PLB515(2001)6 Exotic Matter search EPJdirect C14(2002)1 Results on WIMPS: NaI(Tl) detectors PSD: PLB389(1996)757 Investigation on diurnal effect: N.Cim.A112(1999)1541 Annual Modulation Signature: PLB424(1998)195, PLB450(1999)448, PRD61(1999)023512, PLB480(2000)23, PLB509(2001)197, EPJ C18(2000)283, (up to kg d - 4 cycles) EPJ C23 (2002)61, PRD66(2002) : including other kg d (3 cycles) for a total exposure of: kg d Riv. N. Cim. 26 n. 1 (2003) 1-73 (on the web as astro-ph/ )

11 Full substitution of electronics and DAQ in 2000 End of data taking 2002 N. Cim.A112(1999)545 The detectors Glove box for calibration The 100kg NaI(Tl) set-up The installation

12 Main Features of DAMA/NaI (Il Nuovo Cim. A112 (1999) 545) Reduced standard contaminants (e.g. U/Th of order of ppt) by material selection and growth/handling protocols. Each detector coupled - through 10cm long tetrasil-b light guides acting as optical windows - to 2 low background EMI9265B53/FL (special development) 3 diameter PMTs working in coincidence. Detectors inside a sealed Cu box maintained in HP Nitrogen atmosphere in slight overpressure Very low radioactive shields: 10 cm of copper, 15 cm of lead, 1.5 mm Cd foil+ polyethylene/paraffin for neutron shield + around about the whole shield ~ 1 m concrete outside the barrack A plexiglass box encloses the whole shield and is also maintained in HP Nitrogen atmosphere in slight overpressure Installation in air conditioning + huge heat capacity of shield Walls, floor etc. of inner installation sealed by Supronyl ( cm 2 /s permeability). Calibration using the upper glove-box (equipped with compensation chamber) in HP Nitrogen atmosphere in slight overpressure calibration fi in the same running conditions as the production runs. Each PMT works at single photoelectron level. Considered software energy threshold: 2 kev. Pulse shape recorded over 3250 ns by Transient Digitizers. Monitoring and alarm system continuously operating by selfcontrolled computer processes. Data collected from low energy up to MeV region, despite the hardware optimization was done for the low energy. + electronics and DAQ fully renewed in summer 2000

13 New DAQ and electronic chain after August 2000 DAQ: - Computer: Workstation Digital Alpha - Bus: GPIB - Mainframe: VXI e CAMAC I-F GPIB-VXI VXI Workstation alpha PCI-GPIB CAMAC I-F GPIB-CAMAC Electronic Chain: - Installation of Waveform Analyzer Tektronix TVS641A for bus VXI, 4 channels, Sample rate = 1 Gsample/s, 8 bit, band width 250 MHz, 1channel for each crystal

14 PMT 1 Crystal 1 PMT 2 Preamp Gain 10 L2 L1 Preamp Gain 10 L3 Light guide R 1KΩ L4 L2 A 1 A 2 New electronic chain after August 2000 Cable line L5 F 1 Cable line L6 F2 Cable line L7 Main Trigger gate 1 L8 L9 L10 L11 L12 Delay line 200ns F 3 L19 Gate ADC 1 CAMAC Analog signal from crystal 1 L13 Delay line 200ns Main Trigger Delay gate 2 line 200ns L16 TFA 1 L20 TFA 2 WA 1 VXI In 1 ADC 2 CAMAC Gate Main Trigger gate 3 L14 Discrim 1 L17 L21 Discrim 2 ADC 3 CAMAC Gate L15 L18 L22 L23 L28 OR enable 1 Line CAMAC AND 1 L24 Gate 1 500us L25 L26 L27 In 1 IR pattern recognition Scaler 1 CAMAC Single Trigger crystal 1 Single Trigger crystal 1 X 9 sing cryst 1 sing cryst 2 sing cryst 3 sing cryst 4 sing cryst 5 T sing cryst 6 T sing cryst 7 sing cryst 8 T sing cryst 9 T sing cryst 10 sing cryst 11 sing cryst 12 T sing cryst 13 SA SA Analog SUM OR 1 from AND15 AND 14 Gate 500us 1 < E < 90 kev DGG IR input AND 16 X 9 AND 15 Gate open R Scaler Gate 600ns Gate 50ns D 1us Reset ACQ Line CAMAC Gate 3us Gate 3us AND 17 AND 18 Main Trig gate1 Main Trig gate2 Main Trig gate3 STROBE IR trigger TD1 trigger TD2 SA Gate 3us AND 19 trigger TD3

15 Advantage of the ~100 kg NaI(Tl) expt Knowledge of the physical energy threshold (external kev range sources + low energy Compton electrons) Noise identification (high # ph.el./kev + pulse time structures) Measurability of the software cut efficiencies (by irradiating the crystal with γ sources and Compton e - ) Knowledge of the needed efficiencies Knowledge of the sensitive volume Quenching factors measured (by irradiating a detector from the same growth with neutrons, inducing recoils in the whole sensitive volume)

16 Main procedures of the DAMA data taking for the WIMP annual modulation signature data taking of each annual cycle starts from autumn/winter (when cosw(t-t 0 ) 0) toward summer (maximum expected). routine calibrations for energy scale determination, for acceptance windows efficiencies, etc. by means of radioactive sources each ~ 10 days collecting typically ~10 5 evts/kev/detector + intrinsic calibration from 210 Pb by summing each time the data taken during ~ 7 days + periodical Compton calibrations, etc. continuous on-line monitoring of all the running parameters with automatic alarm to operator if any out of allowed range. N.Cim.A112(1999)545, PLB424(1998)195, PLB450(1999)448, PRD61(1999)023512, PLB480(2000)23, PLB509(2001)197, EPJ C18(2000)283, EPJ C23 (2002)61, PRD66(2002)043503, Riv.N.Cim. 26 n. 1 (2003) 1-73

17 100 kg DAMA/NaI data takings PERIOD STATISTICS REFERENCES (kg day) DAMA/NaI PLB389(1996) 757 (PSD) partially winter overlapped DAMA/NaI-1 + PLB424(1998) summer DAMA/NaI-2 ~ November PLB450(1999)440 to end of July PRD61(1999) DAMA/NaI-3 ~ middle August PLB480(2000) 23 to end September DAMA/NaI-4 ~ middle October idem to second half August Cumulative idem + PLB509(2001) 197+ EPJ C18 (2000)283 EPJ C 23 (2002)61+PRD66(2002) NEW DAMA/NaI ~ August to end of the next July electronics and DAQ fully renewed) DAMA/NaI-6 DAMA/NaI ~ November to end of July ~ August to end of the next July TOTAL EXPOSURE Riv. N.Cim. 26 n.1 (2003)1-73 (on the web as astro-ph/ )

18 DAMA/NaI out of operation The switching off of the ~100kg NaI(Tl) set-up at end of July 2002 Opening the shield Dismounting the ~100kg NaI(Tl) set-up in August 2002

19 DAMA/NaI NaI-1 1 to -7 Annual modulation of the rate: the model independent result Residuals of the rate vs time and energy kg d Riv. N. Cim. 26 n.1. (2003) 1-73 Acos[w (t-t 0 )] ; continuous lines: t 0 = d, T = 1.00 y 2-4 kev 2-5 kev Time (day) fitted: A = ( ) cpd/kg/kev fitted: A = ( ) cpd/kg/kev Time (day) 2-6 kev P(A=0)= c 2 /dof=71/37 fitted: A = ( ) cpd/kg/kev fitted (all parameters free): A = ( ) cpd/kg/kev ; t = ( ) d ; T = ( ) y Time (day) The data favor the the presence of of a modulated behavior with proper features at at 6.3σ C.L.

20 Model-independent residual rate for single hit events Results of the fits keeping all parameters free: (2-4) kev A = ( ) cpd/kg/kev t 0 = (125 30) d T = ( ) y (2-5) kev A = ( ) cpd/kg/kev t 0 = (140 30) d T = ( ) y (2-6) kev A = ( ) cpd/kg/kev t 0 = (140 22) d T = ( ) y

21 Model-independent single hit residual rate in a single annual cycle Initial time 7th August Total Exposure: kg d 6.3s C.L. for t 0 = d and T = 1.00 y: A = ( ) cpd/kg/kev for t 0 = d and T = 1.00 y: A = -( ) cpd/kg/kev A clear modulation is present in the lowest-energy energy region, while it is absent just above

22 Power spectrum of residuals (according to Ap. J. 263(1982) 835; Ap. J. 338 (1989) 277) 2-6 kev Treatment of the experimental errors and time binning included here Total exposure: kg d Principal mode d -1 1 y -1

23 Power spectrum of residuals (according to Ap. J. 263(1982) 835; Ap. J. 338 (1989) 277) 6-14 kev Treatment of the experimental errors and time binning included here No modulation effect found (only aliasing peaks present)

24 Statistical distribution of the modulation amplitudes (S( m ) 2-6 kev 2-14 kev a) S m for each detector, each annual cycle and each considered energy bin (here 0.25 kev) b) <S m > = mean values over the detectors and the annual cycles for each energy bin; s = error associated to the S m Individual S m values follow a normal distribution since (S m -<S m >)/s is distributed as a Gaussian with a unitary standard deviation S m statistically well distributed in all the crystals, in all the data-taking periods and energy bins

25 Analysis of multiple hits events in the region of the signal In DAMA/NaI-6 and 7 each detector has its own TD (multiplexer system removed) pulse profiles of multiple events acquired (total exposure: kg d). Analysis on multiple events (multiplicity > 1) The same analysis procedure as the one followed for single hit events just one difference: recoils induced by WIMPs do not belong to this class of events, that is: multiple-hits events = WIMPs events switched off multi-hit evts modulation amplitude (2-6 kev) = -(3.9 ± 7.9) 10-4 cpd/kg/kev 2-6 kev residuals Residuals for multiple hits events (DAMA/NaI-6 and 7) Residuals for single hits events (DAMA/NaI-1 to 7) Mod ampl. = (0.0195±0.0031) cpd/kg/kev

26 The Stability Parameters: DAMA/NaI-7 All amplitude well compatible with zero + no effect can mimic the annual modulation Temperature Nitrogen flux External Radon Pressure Hardware Rate Running conditions stable at level < 1% Parameters distribution

27 The Stability Parameters Time behaviour modulation amplitudes obtained by fitting the time behaviours of main running parameters, acquired with the production data, when including a WIMP-like modulation Running conditions stable at a level better than 1% All the measured amplitudes well compatible with zero + no effect can mimic the annual modulation (for the other annual cycles see ref: PLB424(1998)195, PLB450(1999)448, PLB480(2000)23,EPJC18(2000)283)

28 Temperature underground T largely stable during the installation site detectors in Cu housings directly in contact with multiton shield fi huge heat capacity (»10 6 cal/ 0 C) Experimental installation air conditioned operating T of the detectors continuously controlled amplitudes for a WIMP-like modulation in the operating T of the detectors well compatible with zero Distribution of the relative variations of the operating T of the detectors DAMA/NaI-5, 6 and 7 An effect from temperature can be excluded + Any possible modulation due to temperature would always fail some of the peculiarities of the signature Distribution of the root mean square values of the operating T within periods with the same calibration factors (typically»7days): mean value» 0.05 C Considering the slope of the light output» -0.2%/ C: relative light output variation < 10-4 : < 0.5% S m observed (For electronic noise, for Radon release from the rocks and for environmental bckg see later)

29 Radon/1 Walls and floor of the inner installation sealed in Supronyl (2 x cm 2 /s permeability). Whole shield in plexiglas box maintained in HP Nitrogen atmosphere in slight overpressure with respect to environment Detectors in the inner Cu box in HP Nitrogen atmosphere in slight overpressure with respect to environment Time behaviour of the environmental radon in the inner part of the barrack (from which the detector are excluded!) measured values at level of sensitivity of the used radonmeter amplitudes for a WIMP-like modulation of external Radon (from which the detectors are excluded!) well compatible with zero:

30 Radon/2 Detectors continuously excluded from environmental air since several years (in HP Nitrogen atmosphere) <flux> of order of 250 l/h Over-pressure 2-3 mbar NO WIMP-like modulation amplitude in the time behaviour of external Radon (from which the detectors are excluded), of HP Nitrogen flux and of Cu box pressure (see before) Investigation in Cu-box atmosphere Study of the double coincidences of g s (609&1120 kev) from 214 Bi Radon daughter Rn concentration in Cu-box atmosphere < Bq/m 3 By MC: < cpd/kg/kev@low energy An hypothetical 10% modulation of possible Rn in Cu-box: <0.2% of S m observed + any possible modulation due to Radon would always fail some of the peculiarities of the signature An effect from Radon can be excluded

31 Noise/1 Distribution of variations of total hardware rates of the 9 crystals over the single ph.el. threshold (that is from noise to infinity ) during DAMA/NaI-5, 6, 7 running periods : Cumulative gaussian behaviour fully accounted by expected statistical spread arising from the sampling time used for the rate evaluation s = 0.5% R Hj = hardware rate of j-th detector above single photoelectron <R Hj > = mean of R Hj in the corresponding annual cycle 0.25 Hz amplitudes for a WIMP-like modulation well compatible with zero:

32 Can noise account for the observed modulation effect? DAMA/NaI From the study of the "Hardware Rate" the modulated amplitude (period and phase as for WIMP) is compatible with zero: -(0.06±0.11) 10-2 Hz < Hz (90% CL) Hardware Rate = noise + bckg [up to MeV] + signal [up to 6keV] noise/crystal 0.10 Hz relative modulated amplitude from noise < /9/ (90%CL) even in the worst hypothetical case of 10% residual tail of noise in the data relative modulated amplitude from noise at low energy < < 1% of the observed annual modulation amplitude NO

33 The efficiencies 2-8 kev Distribution of variations of the efficiency values with respect to their mean values during DAMA/NaI-5,6,7 running periods s = 0.5 % Time behaviour: modulation amplitudes obtained by fitting the time behaviours of the efficiencies including a WIMP-like cosine modulation for DAMA/NaI-5, 6, 7 running periods Energy Modulation amplitude DAMA/NaI kev ( ) kev ( ) 10-3 Amplitudes well compatible with zero + cannot mimic the annual modulation

34 The calibration factors Relative variations of the energy calibration factors (tdcal) from the 210 Pb peak - without applying any correction - for all the 9 detectors during DAMA/NaI-5,6,7 running periods gaussian behaviour with s = 0.5% Uncertainties on tdcal for each detector <1% within each 7 days period: additional energy spread s cal σ cal σ = σres + σcal σres 1 + ; 2 σ res Negligible effect considering routine calibrations and energy resolution at low energy Confirmation from MC: maximum relative contribution < (<1% S obs m ) 2 1 σ cal / E 4 E σres / E 20keV No modulation in the energy scale

35 No modulation in the background: these results also account for the bckg component due to neutrons Can a hypothetical background modulation account for the observed effect? Integral rate at higher energy (above 90 kev), R 90 R 90 percentage variations with respect to their mean values for single crystal in the DAMA/NaI-5,6,7 running periods cumulative gaussian behaviour with σ 0.9%, fully accounted by statistical considerations Fitting the behaviour with time, adding a term modulated according period and phase expected for WIMPs: Period Mod. Ampl. DAMA/NaI-5 (0.09±0.32) cpd/kg DAMA/NaI-6 (0.06±0.33) cpd/kg DAMA/NaI-7 -(0.03±0.32) cpd/kg fi consistent with zero + if a modulation present in the whole energy spectrum at the level found in the lowest energy region fi R90 ~ tens cpd/kg fi ~ 100 s far away Energy regions closer to that where the effect is observed Mod. Ampl. (6-10 kev): -( ± ), ( ± ) and ( ± ) cpd/kg/kev for DAMA/NaI-5, DAMA/NaI-6 and DAMA/NaI-7; they can be considered statistically consistent with zero

36 Can a possible thermal neutron modulation account for the observed effect? Ex.: 23 Na(n,g) 24 Na; 23 Na(n,g) 24m Na capture rate = Φ n σ n N T = 0.17 captures/d/kg Φ n /(10-6 n cm -2 s -1 ) 1.4 x 10-3 cpd/kg/kev when Φ n = 10-6 n cm -2 s -1 MC 7 x 10-5 cpd/kg/kev Thermal neutron LNGS: F n = n cm -2 s -1 (N.Cim.A101(1989),959) F n < n cm -2 s -1 (in the DAMA set-up from delayed coincidences see N.Cim.A112(1999),545) E (MeV) Assuming - very cautiously - a 10% thermal neutron modulation: S m (thermal n) < 10-5 cpd/kg/kev (< 0.05% S m observed ) NO In all the cases of neutron captures ( 24 Na, 128 I,...) a possible thermal n modulation induces a variation in all the energy spectrum Excluded by R 90 analysis

37 Can a possible fast neutron modulation account for the observed effect? In the estimate of possible effect of neutron background cautiously not included the 1m concrete moderator, which almost completely surrounds (outside the barrack) the passive shield Elastic scatterings: recoil nuclei capture rate = Φ n σ n N T Measured fast neutron LNGS: Φ n = n cm -2 s -1 (Astropart.Phys.4 (1995),23) By MC: differential counting rate above 2 kev 10-3 cpd/kg/kev Assuming - very cautiously - a 10% neutron modulation: S (fast n) m < 10-4 cpd/kg/kev (< 0.5% S observed m ) NO Moreover, a possible fast n modulation induces a variation in all the energy spectrum Excluded by R 90 analysis Thus, a possible 5% neutron modulation (ICARUS TM03-01) cannot quantitatively contribute to the DAMA/NaI observed signal, even if the neutron flux would be assumed 100 times larger than measured by various authors over more than 15 LNGS

38 Can the m modulation measured by MACRO account for the observed effect? Case of fast neutrons produced by muons F LNGS 20 m m -2 d -1 (±2% modulated) Neutron LNGS: Y= n /m /(g/cm 2 ) (hep-ex/ ) R n = (fast n by m)/(time unit) = F m Y M eff Annual modulation amplitude at low energy due to µ modulation: S m (µ) = R n g ε f E f single 2% /(M setup E) where: g = geometrical factor ε = detection efficiency by elastic scattering f E = energy window (E>2keV) efficiency f single = single hit efficiency Hyp.: M eff = 15 tons g ε f E f single 0.5 (cautiously) Knowing that: M setup =100kg and E=4keV S m (m) < (1 7) 10-5 cpd/kg/kev (< 0.3% S m observed ) NO Moreover, this modulation also induces a variation in other parts of the energy spectrum Excluded by R 90 analysis

39 Summary of the results obtained by the investigation of possible systematics or side reactions in DAMA/NaI-5, 6, 7 Source Main comment Cautious upper limit (90%C.L.) RADON Sealed Cu box in HP <0.2% S m obs Nitrogen atmosphere TEMPERATURE The installation is air- <0.5% S m obs conditioned NOISE Effective noise <1% S m obs rejection ENERGY SCALE Periodical calibrations + continuous monitoring <1% S obs m of 210 Pb peak EFFICIENCIES Regularly measured by <1% S m obs dedicated calibrations BACKGROUND No modulation observed <0.5% S m obs above 6 kev; this limit includes possible effect of thermal and fast neutrons SIDE REACTIONS Muon flux variation measured by MACRO <0.3% S m obs + even if larger they cannot satisfy all the 6 requirements of annual modulation signature Thus, they can not mimic the observed annual modulation effect

40 Summary of the DAMA/NaI Model Independent result: Presence of modulation for 7 annual cycles at ~6.3s CL with the proper distinctive features for a WIMP induced effect The deep investigation has shown absence of known sources of possible systematics and side processes able to mimic the signature All the signature features satisfied by the data over 7 independent experiments of 1 year each one corollary quests for the nature and coupling with ordinary matter of the candidate particle within given model frameworks

41 Some (of the many possible) corollary quests for the candidate particle To investigate the nature and coupling with ordinary matter of the possible WIMP candidate, an effective energy and time correlation analysis of the events has to be performed within given model frameworks THUS uncertainties on models and comparisons r W WIMP velocity distribution and its parameters coupling: SI, SD, mixed SI&SD,preferred inelastic,... scaling laws on cross sections form factors and related parameters spin factors etc. They can affect not only the corollary estimated regions following a positive effect from the WIMP annual modulation signature, but also results given as exclusion plots experimental parameters (typical of each experiment) comparison within particle models

42 Example effect on the exclusion plot when changing the value of a parameter (inside its allowed range) within the same model framework s p (pb) Na Astrop. Phys. 2 (1994) 117 F Top curves: v 0 =180 km/s; v esc =500 km/s Lower curves: v 0 =250 km/s; v esc =1000 km/s v 0 affects mainly the overall rate v esc affects mostly the lower mass region m W (GeV) Similar effect are found for every nucleus and interaction type changing assumptions and/or expt/theoretical parameters

43 WIMP-nucleus elastic scattering SI+SD differential cross sections: dσ de R (v,e R ) = 2G F 2 m N πv 2 dσ de R SI + dσ de R SD = [ Zg p + (A Z )g n ] 2 F SI2 (E R ) + 8 J + 1 a J [ p S p + a n S n ] 2 F SD2 ( E R ) g p,n (a p,n ) effective WIMP-nucleon couplings <S p,n > nucleon spin in the nucleus F 2 (E R ) nuclear form factors m Wp reduced WIMP-nucleon mass Generalized SI/SD WIMP-nucleon cross sections: σ SI = 4 π G 2 Fm 2 Wp g 2 σ SD = 32 3 π 4 G 2 Fm 2 Wp a 2 where: g = g p + g n 2 1 g g p n g p + g n 1 2Z A a = a p 2 + a n 2 tgθ = a n a p g: independent on the used target nucleus since Z/A nearly constant for the nuclei typically used in WIMP direct searches Differential energy distribution: dr ρ v = N W max dσ ρ de T R m v min (E R ) W (v, E de R )vf(v)dv = N W m N T 2 Σ(E R 2m W m R ) I(E R ) Wp Σ(E R ) = A 2 σ SI F 2 SI (E R ) + 4 J +1 3 J σ SD[ S p cosθ + S n sinθ] 2 F 2 where: SD (E R ) v max f (v) I(E R ) = dv v min (E R ) v v max : maximal WIMP velocity in the Earth frame N T : number of target nuclei minimal velocity providing E R recoil energy: f(v): WIMP velocity distribution in the Earth frame (it depends on v e ) v e =v sun +v orb coswt v min = m NE R 2 2m WN

44 The inelastic WIMP nucleus interaction: W + N fi W * + N WIMP candidate suggested by D. Smith and N. Weiner (PRD64(2001)043502) Two mass states c +, c - with d mass splitting WIMP Kinematical constraint for the inelastic scattering of c - on a nucleus with mass m N becomes increasingly severe for low m N dσ dω 1 2 µv2 δ v v thr = 2δ µ Ex. m W =100 GeV m N m Differential energy distribution for SI interaction: G m v [ Zg p + ( A Z) g n] FSI ( q ) F WN = 1 * 2 π Nucleus recoil energy: E g p,n effective WIMP-nucleon couplings dω* differential solid angle in the WIMP-nucleus c.m. frame q 2 = squared threee-momentum transfer R 2 2 vthr vthr cosθ 2 2 2mWN v = 2v v m 2 dσ de R = N 2 [ Zg + ( A Z ) g ] F ( E ) 2 2 G F m N 2 2 p n SI πv Differential energy distribution: * R v thr dr de R = N T ρ m W W v v max min dσ de R ( v, E R ) vf ( v) dv v m E m 1 + = N R WN min ( ER) 2 2mWN mner δ

45 Similar situation for all the target nuclei considered in the field Examples of different Form Factor profiles for 127 I available in literature Take into account the structure of target nuclei In SD form factor: no decoupling between nuclear and WIMP degrees of freedom; dependence on nuclear potential. Example on 127 I nucleus: Spin Independent 2 ( qr n ) /5 e Ae α 2 2 1( qrn) α2( qrn) Helm + (1 Ae ) charge spherical distribution from Helm 2 ( qr ) /5 e n α Ae Spin Dependent + (1 Ae ) 2 2 1( qrn) α2( qrn) thin shell distribution from Ressell et al. Smith et al., Astrop.Phys.6(1996) 87

46 The Spin Factor Spin Factors for some target-nuclei calculated in simple different models Spin factor = Λ 2 J(J+1)/a x 2 (a x = a n or a p depending on the unpaired nucleon) Spin Factors calculated on the basis of Ressell et al. for some of the possible q values considering some target nuclei and two different nuclear potentials Spin factor = Λ 2 J(J+1)/a 2

47 Quenching factor recoil/electron response ratio measured with a neutron source or at a neutron generator Quenching factors, q, measured by neutron sources or by neutron beams for some detectors and nuclei none available so far (assumed 1)

48 Isothermal sphere: the most widely used model only in the WIMP direct search (but not correct) density profile: ρ DM () r r Halo modeling Needed quantities for Dark Matter direct searches: DM local density ρ 0 = ρ DM (R 0 = 8.5 kpc) local velocity v 0 = v rot (R 0 = 8.5kpc) velocity distribution f( v r ) Spherical r DM, isotropic velocity dispersion 2 gravitational potential: Ψ 2 0 log( r ) Maxwellian velocity distribution Evans logarithmic ρ DM v 3R + r () r = 4 π ( ) c G Rc + r v Ψ = () r log( Rc r ) v () r = v 2 2 rot c r ( Rc + r ) Evans power-law ρ DM βψ + () r = 4 π ( ) β 2 2 arc 3 Rc r (1 β) 2 2 ( β + 4)/2 G Rc + r Ψ R Ψ () =,( β 0) β a c 0 r 2 2 β /2 ( Rc + r ) v 2 rot βψ Rr () r = ( R ) β 2 a c 2 2 ( β + 2)/2 c + r Others: ρ DM () r γ ( β γ)/ α α R0 1 + ( R0/ a) = ρ0 α r 1 + ( r/ a) If spherical r DM with non-isotropic velocity dispersion v β = 2 φ vr If Axisymmetric r DM q flatness Triaxial r DM p,q,δ v z Ψ = q ( rz, ) log Rc r 2 v Ψ = + y + z 2 p q ( xyz,, ) log x 2 2 δ = free parameter in spherical limit (p=q=1) quantifies the anisotropy of the velocity dispersion tensor v v 2 φ 2 r 2 + δ = 2 Constraining the models v = (220 ± 50) km s v 0 M v rot M ( r vis M = 100kpc) 1.2 v 0

49 Isothermal sphere Consistent Halo Models Models accounted in the following: very simple but unphysical halo model Several approaches different from the isothermal sphere model: Belli et al. PRD61(2000)023512; VergadosPR83(1998)3597, PRD62(2000)023519;Ullio & Kamionkowski JHEP03(2001)049; GreenPRD63(2001) , Vergados & Owen astroph/ Large number of self-consistent halo models constrained by astrophysical observations (for DAMA/NaI-0 to 4 see PRD66(2002)043503)

50 The allowed local density values Allowed intervals of r 0 (GeV/cm 3 ) for v 0 =170,220,270 km/s, for the halo models considered in the model-dependent analyses given in the following Intervals evaluated considering the density profile and the astrophysical constraints v = (220 ± 50) km s v 0 M v rot M ( r vis M = 100kpc) 1.2 v 0 PRD66(2002)043503

51 Model dependent scenarios investigated here (others( under investigation) Main topics: Halo models as in PRD66(2002) Helm FF for SI coupling Ressel FF (Nijmengen II nuclear potential) calculated for χ + Case A: FF parameters at fixed values and quenching factors at mean measured values Case B: i) 23 Na and 127 I quenching factors from mean values up to +2 times the errors; ii) nuclear radius, r, and nuclear surface thickness parameter, s, in the SI FF from fixed values down to 20%; iii) b parameter in the considered SD FF from fixed value down to 20%. Case C: one of the possible more extreme cases where the Iodine nucleus parameters are fixed at values of case B, while for Sodium nucleus one considers: i) 23 Na quenching factor at the lowest valueavailable in literature (see Table); ii) nuclear radius, r n, and nuclear surface thickness parameter, s, in the used SI FF from central values up to +20%; iii) b parameter in the considered SD FF from fixed value up to +20%. For simplicity, the results are given in terms of allowed regions obtained as superposition of the configurations corresponding to likelihood function values distant more than 4s from the null hypothesis (absence of modulation) in each of the several (but still a limited number of the possible) model frameworks considered here.

52 PRIORS Measured upper limits on the recoil fractions in the DAMA/NaI-0 running period, especially devoted to this investigation Model dependent mass limit for supersymmetric candidates by accelerator experiments: m W > 30 GeV from lower bound on neutralino mass as derived from LEP data in supersymmetric schemes based on GUT assumptions (from DPP2003) but other model assumptions are possible and would imply significant variations of the accelerators bounds as shown in literature also recently e.g. for the case when the gaugino-mass unification at GUT scale is released + candidates other than neutralino are possible. e.g.: an heavy neutrino of the 4-th family; the sneutrino in the Weiner and Smith scenario; even whatever suitable particle not yet foreseen by theory

53 Example of slices of the allowed volume for given m W and q values + Several other possibilities for the SI &SD mixed model framework are open and to be investigated (different SD-FF (a p & a n ), g n = g p?, different halo models, etc.) including all the existing uncertainties much larger regions (and volumes) are obtained The use e.g of more favourable form factors than those we considered here alone would move the region towards lower cross sections At present either a purely SI or a purely SD or a mixed SI&SD configurations are supported by the data General case: WIMP with SI & SD couplings (Na and I are fully sensitive to SD interaction, on the contrary of e.g. Ge and Si,) The result is an allowed volume in the space (xs SI, sx SD, m W ) for each possible q (tgq = a n /a p, with 0=q<p) x = r W / r 0, x = 1 fraction of amount of local WIMP density Several consistent halo models including halo rotation (see before) Cases A, B and C θ=0 (a n =0, a p 0) θ=π/4 (a n =a p ) θ=π/2 (a n 0, a p =0) θ=2.435 (a n /a p = -0.85, Z 0 coupl.)

54 Example of how the regions have been built The figure shows the superposition of the slices obtained for each one of the model framework considered in the case of m W =90 GeV and θ = (pure Z 0 coupling) The inclusion of other existing uncertainties on parameters and models would further extend the region: e.g. the use of more favourable form factors than those we considered here alone would move the region towards lower cross sections

55 WIMP with dominant SI coupling Best-fit values of cross section and WIMP mass span over a large range depending on the model framework. Just as an example: triaxial D2, max r 0, low v 0 and parameters case C: m W =( ) GeV and xs SI =( ) 10-6 pb The inclusion of other existing uncertainties on parameters and models would further extend the region: e.g. the use of more favourable FF than those considered here alone would move the region towards lower cross sections x = r W / r 0, x = 1 fraction of amount of local WIMP density Several consistent halo models including halo rotation (see before) Cases A, B and C + see previous transparencies Region potentially of interest for a neutralino in supersymmetric schemes where assumption on gaugino-mass unification at GUT is released and for generic WIMP DAMA/NaI-0 to 7 Model dependent lower bound on neutralino mass as derived from LEP data in supersymmetric schemes based on GUT assumptions (DPP2003) higher mass region allowed for low v 0, every set of parameters values and the halo models: Evans logarithmic C1 and C2 co-rotating, triaxial D2 and D4 non-rotating, Evans power-law B3 in set A

56 An example of the effect induced by a non-zero SD component on the allowed SI regions Example obtained considering Evans logarithmic axisymmetric C2 halo model with v 0 = 170 km/s, ρ 0 max and parameters of set A The different regions refer to different SD contributions with θ=0 There is no meaning in bare comparison between regions allowed in experiments sensitive to SD coupling and exclusion plots achieved by experiments that are not. The same is when comparing regions allowed by experiments whose target-nuclei have unpaired proton with exclusion plots quoted by experiments using target-nuclei with unpaired neutron where θ 0 or θ π. a) s SD = 0 pb; b) s SD = 0.02 pb; c) s SD = 0.04 pb; d) s SD = 0.05 pb; e) s SD = 0.06 pb; f) s SD = 0.08 pb; A small SD contribution drastically moves the allowed region in the plane (m W, xs SI ) towards lower SI cross sections (xs SI < 10-6 pb)

57 Supersymmetric expectations in MSSM - purely SI coupling - (mass below 50 GeV obtained when releasing the gaugino mass unification at GUT scale) scatter plot of theoretical configurations from hep-ph/

58 WIMP with dominant SD couplings Region allowed in the space (m W, ξσ SD, θ) Here example of slices for only 4 (θ=0, π/4, π/2, 2.435) values of θ (which can range from 0 to π) Several consistent halo models including halo rotation (see before) Cases A, B and C + see previous transparencies Regions above 200 GeV allowed for low v 0, for every set of parameters values and for Evans logarithmic C2 co-rotating halo models Best-fit values of cross section and WIMP mass span over a large range depending on the model framework The inclusion of other existing uncertainties on parameters and models would further extend the region: e.g. the use of more favourable FF than those we considered here alone would move the region towards lower cross sections DAMA/NaI-0 to 7

59 An example of the effect induced by a non-zero SI component on the allowed SD regions Example obtained considering Evans logarithmic axisymmetric C2 halo model with v 0 = 170 km/s, ρ 0 max and parameters of set A for θ=0. The different regions refer to different SI contributions The accounting for the uncertainties, e.g., on the spin factors, different SD form factors would extend the region allowed and move it towards lower ξσ SD values a) s SI = 0 pb; b) s SI = pb; c) s SI = pb; d) s SI = pb; e) s SI = pb; f) s SI = 10-6 pb; A small SI contribution drastically moves the allowed region in the plane (m W, xs SD ) towards lower SD cross sections (xs SD < 0.1 pb)

60 v esc fixed but its uncertainties can play an important role, extending the allowed regions region largely lies in δ regions where e.g. Ge is disfavoured Best-fit values of cross section and d for given m W span over a large range depending on the model framework. Just as an example: m W = 70 GeV in NFW B5 halo model with low v 0, max r 0 and parameters as in case B: d=( ) kev, xs p =( ) 10-5 pb The inclusion of other existing uncertainties on parameters and models would further extend the region: e.g. the use of a more favourable SI form factor for iodine would move the regions towards lower cross-sections WIMP with preferred SI inelastic interaction: W + N fi W * + N Region allowed in the space (m W, xs p,d) ξ = ρ W / ρ 0, ξ = 1 fraction of amount of local WIMP density Here examples of slices for some m W values Several consistent halo models including halo rotation (see before) Cases A, B and C + see previous transparencies

61 HEAT data as analysed in PRD65(2002) Some positive hints from indirect searches not in conflict with DAMA (Note that the interpretation of these hints and the derived WIMP mass and cross section depend on bckg modeling, on spatial/velocity WIMP distribution in the galactic halo, etc.) A. Morselli et al., astro-ph/

62 PMT +HV divider Installing LIBRA detectors The The new newlibra set-up set-up ~250 ~250 kg kg NaI(Tl) (Large (Largesodium Iodide IodideBulk for forrare RAreprocesses) in in the thedama experiment As a result of a new R&D for radiopurer NaI(Tl) by exploiting new chemical/physical radiopurification techniques (all operations involving crystals and PMTs - including photos - in HP Nitrogen atmosphere) storing new crystals Improving installation etching staff at work

63 Corollary model dependent quest for a candidate: WIMPs with mixed SI/SD or pure SI or pure SD coupling as well as WIMPs with preferred inelastic scattering in some of the many possible model frameworks. not exhaustive - other scenarios possible and under investigations Summary Successfully running the ~100kg NaI(Tl) set-up over 7 annual cycles (~ 1.1 x 10 5 kg day) The model independent result: presence of a WIMP component in the galactic halo supported at 6.3 s C.L. by the WIMP annual modulation signature. No known systematics nor side reactions able to mimic the signature found - nor suggested by anyone. now running DAMA/LIBRA (~250 kg NaI(Tl)) since march 2003 & a new R&D for further NaI(Tl) radiopurifications toward 1 ton set-up proposed in 1996