The annual modulation: a model independent signature for the investigation of DM particles component in the galactic halo

Transcription

1 The annual modulation: a model independent signature for the investigation of DM particles component in the galactic halo With the present technology, the annual modulation is the main model independent signature for the DM signal. Although the modulation effect is expected to be relatively small a suitable large-mass, low-radioactive set-up with an efficient control of the running conditions can point out its presence. Requirements: 1) Modulated rate according cosine 2) In low energy range 3) With a proper period (1 year) 4) With proper phase (about 2 June) 5) Just for single hit events in a multidetector set-up 6) With modulation amplitude in the region of maximal sensitivity must be <7% for usually adopted halo distributions, but it can be larger in case of some possible scenarios June Drukier, Freese, Spergel PRD86; Freese et al. PRD88 60 v (t) = v sun + v orb cosγcos[ω(t-t 0 )] December dr Sk[ η( t)] = der S0, k + Sm, k cos[ ω( t t0)] de ΔE k R v sun ~ 232 km/s (Sun vel in the halo) v orb = 30 km/s (Earth vel around the Sun) γ = π/3, ω = 2π/ T, T = 1 year t 0 = 2 nd June (when v is maximum) the DM annual modulation signature has a different origin and peculiarities (e.g. the phase) than those effects correlated with the seasons To mimic this signature, spurious effects and side reactions must not only - obviously - be able to account for the whole observed modulation amplitude, but also to satisfy contemporaneously all the requirements

2 Collaboration: DAMA set-ups an observatory for rare LNGS DAMA/LIBRA (DAMA/NaI) DAMA/LXe DAMA/R&D DAMA/Crys DAMA/Ge Roma Tor Vergata, Roma La Sapienza, LNGS, IHEP/Beijing + by-products and small scale expts.: INR-Kiev + other institutions + neutron meas.: ENEA-Frascati, ENEA-Casaccia + in some studies on ββ decays (DST-MAE and Inter-Universities project): IIT Kharagpur and Ropar, India web site:

3 Collaboration: Roma Tor Vergata, Roma La Sapienza, LNGS, IHEP/Beijing (+ Jinggangshan Univ) + by-products and small scale expts.: INR-Kiev + neutron meas.: ENEA-Frascati + in some studies on ββ decays (DST-MAE and Inter- Universities project): IIT Kharagpur and Ropar, India DAMA/CRYS DAMA/R&D DAMA/LXe DAMA/Ge DAMA/NaI DAMA/LIBRA

4 LABORATORI NAZIONALI DEL GRAN SASSO - INFN Largest underground laboratory for astroparticle physics LNGS ROME Roma-L Aquila-Teramo highway: tunnel under Gran Sasso mountain, 10.4 km long In 1979 A. Zichichi proposed to the Parliament the project of a large underground laboratory close to the Gran Sasso highway tunnel, then under construction. In 1982 the Parliament approved the construction, finished in 1987 In 1989 first experiments (GALLEX, MACRO, LVD,...) started taking data m rock coverage - cosmic µ reduction= 10 6 (i.e. 1 /m 2 h) - underground area: m 2 - external facilities - easy access - thoudand scientists from about 30 countries - Permanent staff = hundred positions Research lines Neutrino physics (mass, oscillations, stellar physics, solar ν s, ν s from beam, ν s from supernovae) Dark matter Rare processes Nuclear reactions of astrophysics interest Geophysics Biology Gravitational waves (in future)

5 Main results obtained by DAMA in the search for rare processes First or improved results in the search for 2β decays of ~30 candidate isotopes: 40 Ca, 46 Ca, 48 Ca, 64 Zn, 70 Zn, 100 Mo, 96 Ru, 104 Ru, 106 Cd, 108 Cd, 114 Cd, 116 Cd, 112 Sn, 124 Sn, 134 Xe, 136 Xe, 130 Ba, 136 Ce, 138 Ce, 142 Ce, 156 Dy, 158 Dy, 180 W, 186 W, 184 Os, 192 Os, 190 Pt and 198 Pt The best experimental sensitivities in the field for 2β decays with positron emission First observation of α decays of 151 Eu (T 1/2 = yr) with a CaF 2 (Eu) scintillator and of 190 Pt to the first excited level (E exc =137.2 kev) of 186 Os (T 1/2 = yr) Investigations of rare β decays of 113 Cd (T 1/2 = yr), 113m Cd with CdWO 4 scintillator and 48 Ca with a CaF 2 (Eu) detector Observation of correlated e + e - pairs emission in α decay of 241 Am (A e+e- /A α ) CNC processes in 127 I, 136 Xe, 100 Mo and 139 La; Search for 7 Li solar axions using resonant absorption in LiF crystal Search for spontaneous transition of 23 Na and 127 I nuclei to superdense state; 113 Cd β Search for cluster decays of 127 I, 138 La and 139 La; Search for PEP violating processes in sodium and in iodine; Search for N, NN, NNN decay into invisible channels in 129 Xe and 136 Xe Many others are in progress

6 The pioneer DAMA/NaI: 100 kg highly radiopure NaI(Tl) Performances: N.Cim.A112(1999) , EPJC18(2000)283, Riv.N.Cim.26 n. 1(2003)1-73, IJMPD13(2004)2127 Results on rare processes: Possible Pauli exclusion principle violation PLB408(1997)439 CNC processes PRC60(1999) Electron stability and non-paulian transitions in Iodine atoms (by L-shell) PLB460(1999)235 Search for solar axions PLB515(2001)6 Exotic Matter search EPJdirect C14(2002)1 Search for superdense nuclear matter EPJA23(2005)7 Search for heavy clusters decays EPJA24(2005)51 Results on DM particles: PSD PLB389(1996)757 Investigation on diurnal effect N.Cim.A112(1999)1541 Exotic Dark Matter search PRL83(1999)4918 data taking completed on July 2002, last data release Still producing results Annual Modulation Signature PLB424(1998)195, PLB450(1999)448, PRD61(1999)023512, PLB480(2000)23, EPJC18(2000)283, PLB509(2001)197, EPJC23(2002)61, PRD66(2002)043503, Riv.N.Cim.26 n.1 (2003)1, IJMPD13(2004)2127, IJMPA21(2006)1445, EPJC47(2006)263, IJMPA22(2007)3155, EPJC53(2008)205, PRD77(2008)023506, MPLA23(2008)2125 Model independent evidence of a particle DM component in the galactic halo at 6.3 C.L. total exposure (7 annual cycles) 0.29 ton yr

7 The DAMA/LIBRA set-up ~250 kg NaI(Tl) (Large sodium Iodide Bulk for RAre processes) As a result of a 2nd generation R&D for more radiopure NaI(Tl) by exploiting new chemical/physical radiopurification techniques (all operations involving - including photos - in HP Nitrogen atmosphere) Residual contaminations in the new DAMA/LIBRA NaI(Tl) detectors: 232 Th, 238 U and 40 K at level of g/g Ø Radiopurity, performances, procedures, etc.: NIMA592(2008)297, JINST 7 (2012) Ø Results on DM particles, Annual Modulation Signature: EPJC56(2008)333, EPJC67(2010)39, EPJC73(2013)2648. Related results: PRD84(2011)055014, EPJC72(2012)2064, IJMPA28(2013) , EPJC74(2014)2827, EPJC74(2014)3196, EPJC75(2015)239, EPJC75(2015)400 Ø Results on rare processes: PEPv: EPJC62(2009)327; CNC: EPJC72(2012)1920; IPP in 241 Am: EPJA49(2013)64

8 LNGS

9 DAMA/LIBRA phase2 Upgrade on Nov/Dec 2010: all PMTs replaced with new ones of higher Q.E. JINST 7(2012)03009 Q.E. of the new PMTs: nm 36 peak

10 25 x 9.7 kg NaI(Tl) in a 5x5 matrix two Suprasil-B light guides directly coupled to each bare crystal two new high Q.E. PMTs for each crystal working in coincidence at the single ph. el. threshold 6-10 phe/kev; 1 kev software energy threshold The DAMA/LIBRA phase2 set-up Installation Glove-box for calibration NIMA592(2008)297, JINST 7(2012)03009, IJMPA31(2017)issue31 Electronics + DAQ Three-level system to exclude Radon from the detectors Calibrations in the same running conditions as prod runs Never neutron source in DAMA installations Installation in air conditioning + huge heat capacity of shield Monitoring/alarm system; many parameters acquired with the production data Whole setup decoupled from ground Fragmented set-up: single-hit events = each detector has all the others as anticoincidence Dismounting/Installing protocol in HPN 2 All the materials selected for low radioactivity Multiton-multicomponent passive shield (>10 cm of OFHC Cu, 15 cm of boliden Pb + Cd foils, 10/40 cm Polyethylene/paraffin, about 1 m concrete, mostly outside the installation) Pulse shape recorded by Waweform Analyzer Acqiris DC270 (2chs per detector), 1 Gs/s, 8 bit, bandwidth 250 MHz both for single-hit and multiple-hit events Data collected from low energy up to MeV region, despite the hardware optimization for low energy DAQ with optical readout New electronic modules

11 Some on residual contaminants in new ULB NaI(Tl) detectors e α α/e pulse shape discrimination has practically 100% effectiveness in the MeV range The measured α yield in the new DAMA/LIBRA detectors ranges from 7 to some tens α/kg/day Second generation R&D for new DAMA/LIBRA crystals: new selected powders, physical/ chemical radiopurification, new selection of overall materials, new protocol for growing and handling live time = 570 h Th residual contamination From time-amplitude method. If 232 Th chain at equilibrium: it ranges from 0.5 ppt to 7.5 ppt 238 U residual contamination First estimate: considering the measured α and 232 Th activity, if 238 U chain at equilibrium 238 U contents in new detectors typically range from 0.7 to 10 ppt 238 U chain splitted into 5 subchains: 238 U 234 U 230 Th 226 Ra 210 Pb 206 Pb Thus, in this case: (2.1±0.1) ppt of 232 Th; (0.35 ±0.06) ppt for 238 U and: (15.8±1.6) µbq/kg for 234 U Th; (21.7±1.1) µbq/kg for 226 Ra; (24.2±1.6) µbq/kg for 210 Pb nat K residual contamination The analysis has given for the nat K content in the crystals values not exceeding about 20 ppb double coincidences 129 I and 210 Pb 129 I/ nat I for all the new detectors 210 Pb in the new detectors: (5 30) µbq/kg. No sizable surface pollution by Radon daugthers, thanks to the new handling protocols... more on NIMA592(2008)297

12 DAMA/LIBRA calibrations Low energy: various external gamma sources ( 241 Am, 133 Ba) and internal X-rays or gamma s ( 40 K, 125 I, 129 I), routine calibrations with 241 Am Linearity Energy resolution 3.2 kev Internal 40 K Tagged by an adjacent detector Internal 125 I first months 40.4 kev 67.3 kev 59.5 kev 81 kev 241 Am 133 Ba σ LE E ( ± 0.035) 3 ( ) 10 = + ± EkeV ( ) High energy: external sources of gamma rays (e.g. 137 Cs, 60 Co and 133 Ba) and gamma rays of 1461 kev due to 40 K decays in an adjacent detector, tagged by the 3.2 kev X-rays 30.4 kev The curves superimposed to the experimental data have been obtained by simulations 662 kev 1173 kev 137 Cs 60 Co 1332 kev Linearity Energy resolution The signals (unlike low energy events) for high energy events are taken only from one PMT 356 kev 1461 kev 2505 kev 133 Ba 40 K σ HE E ( 1.12 ± 0.06) 4 ( 17 23) 10 = + ± EkeV ( ) Thus, here and hereafter kev means kev electron equivalent 81 kev

13 DAMA/LIBRA-phase2 data taking Second upgrade at end of 2010: all PMTs replaced with new ones of higher Q.E. ü Fall 2012: new preamplifiers installed + special trigger modules. ü Calibrations 6 a.c.: 1.3 x 10 8 events from sources ü Acceptance window eff. 6 a.c.: 3.4 x 10 6 events ( 1.4 x 10 5 events/kev) Energy 60 kev mean value: prev. PMTs 7.5% (0.6% RMS) new HQE PMTs 6.7% (0.5% RMS) Annual Cycles Period I Dec 23, 2010 Sept. 9, 2011 II Nov. 2, 2011 Sept. 11, 2012 III Oct. 8, 2012 Sept. 2, 2013 IV Sept. 8, 2013 Sept. 1, 2014 V Sept. 1, 2014 Sept. 9, 2015 VI Sept. 10, 2015 Aug. 24, 2016 VII Sept. 7, 2016 Sept. 25, 2017 JINST 7(2012)03009 Mass (kg) Exposure (α β 2 ) commissioning Exposure first data release of DAMA/LIBRA-phase2: 1.13 ton x yr Exposure DAMA/NaI+DAMA/LIBRA-phase1+phase2: 2.46 ton x yr

14 DM model-independent Annual Modulation Result experimental residuals of the single-hit scintillation events rate vs time and energy DAMA/LIBRA-phase2 (1.13 ton yr) Absence of modulation? No 1-3 kev: χ 2 /dof=127/52 P(A=0) = kev: χ 2 /dof=150/52 P(A=0) = kev: χ 2 /dof=116/52 P(A=0) = Fit on DAMA/LIBRA-phase2 Acos[ω(t-t 0 )] ; continuous lines: t 0 = d, T = 1.00 y 1-3 kev A=(0.0184±0.0023) cpd/kg/kev χ 2 /dof = 61.3/ σ C.L. 1-6 kev A=(0.0105±0.0011) cpd/kg/kev χ 2 /dof = 50.0/ σ C.L. 2-6 kev A=(0.0095±0.0011) cpd/kg/kev χ 2 /dof = 42.5/ σ C.L. The data of DAMA/LIBRA-phase2 favor the presence of a modulated behavior with proper features at 9.5σ C.L.

15 DM model-independent Annual Modulation Result experimental residuals of the single-hit scintillation events rate vs time and energy DAMA/LIBRA-phase1+DAMA/LIBRA-phase2 (2.17 ton yr) Absence of modulation? No 2-6 kev: χ 2 /dof=199.3/102 P(A=0) = Fit on DAMA/LIBRA-phase1+ Acos[ω(t-t 0 )] ; continuous lines: t 0 = d, T = 1.00 y 2-6 kev DAMA/LIBRA-phase2 A=(0.0095±0.0008) cpd/kg/kev χ 2 /dof = 71.8/ σ C.L. The data of DAMA/LIBRA-phase1 +DAMA/LIBRA-phase2 favor the presence of a modulated behavior with proper features at 11.9 σ C.L.

16 Releasing period (T) and phase (t 0 ) in the fit ΔE A(cpd/kg/keV) T=2π/ω (yr) t 0 (day) C.L. (1-3) kev ± ± ±7 8.0σ DAMA/LIBRA-ph2 DAMA/LIBRA-ph1 + DAMA/LIBRA-ph2 DAMA/NaI + DAMA/LIBRA-ph1 + DAMA/LIBRA-ph2 (1-6) kev ± ± ±6 9.6σ (2-6) kev ± ± ±7 8.7σ (2-6) kev ± ± ±5 12.0σ (2-6) kev ± ± ±5 12.9σ Acos[ω(t-t 0 )] DAMA/NaI (0.29 ton x yr) DAMA/LIBRA-ph1 (1.04 ton x yr) DAMA/LIBRA-ph2 (1.13 ton x yr) total exposure = 2.46 ton yr

17 No Modulation above 6 kev A=(1.0±0.6) 10-3 cpd/kg/kev DAMA/LIBRA-phase2 Rate behaviour above 6 kev Mod. Ampl. (6-14 kev): cpd/kg/kev ( ± ) DAMA/LIBRA-ph2_2 ( ± ) DAMA/LIBRA-ph2_3 ( ± ) DAMA/LIBRA-ph2_4 -( ± ) DAMA/LIBRA-ph2_5 ( ± ) DAMA/LIBRA-ph2_6 ( ± ) DAMA/LIBRA-ph2_7 statistically consistent with zero DAMA/LIBRA-phase2 No modulation in the whole energy spectrum: studying integral rate at higher energy, R 90 R 90 percentage variations with respect to their mean values for single crystal in the DAMA/LIBRA running periods Fitting the behaviour with time, adding a term modulated with period and phase as expected for DM particles: consistent with zero + if a modulation present in the whole energy spectrum at the level found in the lowest energy region R 90 tens cpd/kg 100 σ far away Period Mod. Ampl. DAMA/LIBRA-ph2_2 (0.12±0.14) cpd/kg DAMA/LIBRA-ph2_3 -(0.08±0.14) cpd/kg DAMA/LIBRA-ph2_4 (0.07±0.15) cpd/kg DAMA/LIBRA-ph2_5 -(0.05±0.14) cpd/kg DAMA/LIBRA-ph2_6 (0.03±0.13) cpd/kg DAMA/LIBRA-ph2_7 -(0.09±0.14) cpd/kg No modulation above 6 kev This accounts for all sources of bckg and is consistent with the studies on the various components σ 1%, fully accounted by statistical considerations

18 DM model-independent Annual Modulation Result DAMA/LIBRA-phase2 (1.13 ton yr) Multiple hits events = Dark Matter particle switched off A=(0.0004±0.0004) cpd/kg/kev A=( ± ) cpd/kg/kev Single hit residual rate (red) vs Multiple hit residual rate (green) Clear modulation in the single hit events; No modulation in the residual rate of the multiple hit events This result offers an additional strong support for the presence of DM particles in the galactic halo further excluding any side effect either from hardware or from software procedures or from background

19 The analysis in frequency (according to PRD75 (2007) ) To perform the Fourier analysis of the data in a wide region of frequency, the single-hit scintillation events have been grouped in 1 day bins The whole power spectra up to the Nyquist frequency DAMA/NaI + DAMA/LIBRA-(ph1+ph2) (20 yr) total exposure: 2.46 ton yr Zoom around the 1 y 1 peak 90% C.L. 90% C.L. Principal mode: d -1 1 y -1 90% C.L. Green area: 90% C.L. region calculated taking into account the signal in (2-6) kev Clear annual modulation in (2-6) kev + only aliasing peaks far from signal region

20 Modulation amplitudes S m as function of the energy The likelihood function of the single-hit scintillation events in the k-th energy bin is defined as: L k µ = e µ ijk ij N N ijk ijk! N ijk follows a Poissonian distribution with expectation value: ijk ijk N ijk is the number of events collected in the i-th time interval, by the j-th detector and in the k-th energy bin. [ bjk + Rk ( t) ] M jδtiδeε jk = [ bjk + S0, k + Sm, k cosω( ti t0) ] M jδti Eε jk µ = Δ The b jk are the background contributions, M j is the mass of the j-th detector, Δt i is the detector running time during the i-th time interval, ΔE is the chosen energy bin, ε jk is the overall efficiency. The usual procedure is to minimize the function y k =-2ln(L k ) - const for each energy bin; the free parameters of the fit are the (b jk + S 0,k ) contributions and the S m,k parameter. The S m,k is the modulation amplitude of the modulated part of the signal obtained by maximum likelihood method over the data considering T=2π/ω=1 yr and t 0 = day.

21 Energy distribution of the modulation amplitudes Max-likelihood analysis R(t) = S 0 + S m cos"# ω ( t t ) 0 $ % heret=2π/ω=1 yr and t 0 = day DAMA/NaI + DAMA/LIBRA-phase1 vs DAMA/LIBRA-phase2 ΔE = 0.5 kev bins χ 2 (6-20 kev)/dof = 35.8/28 (P-value=15%) χ 2 (6-20 kev)/dof = 29.8/28 (P-value=37%) The two S m energy distributions obtained in DAMA/NaI+DAMA/LIBRA-ph1 and in DAMA/LIBRA-ph2 are consistent in the (2 20) kev energy interval: χ 2 = Σ (r 1 r 2 ) 2 /(σ 12 +σ 22 ) (2-20) kev χ 2 /d.o.f.=32.7/36 (P=63%) (2-6) kev χ 2 /d.o.f.=10.7/8 (P=22%)

22 Energy distribution of the modulation amplitudes Max-likelihood analysis R(t) = S 0 + S m cos"# ω ( t t ) 0 $ % heret=2π/ω=1 yr and t 0 = day DAMA/NaI + DAMA/LIBRA-phase1 + DAMA/LIBRA-phase2 (2.46 ton yr) ΔE = 0.5 kev bins A clear modulation is present in the (1-6) kev energy interval, while S m values compatible with zero are present just above The S m values in the (6 14) kev energy interval have random fluctuations around zero with χ 2 equal to 19.0 for 16 degrees of freedom (upper tail probability 27%). In (6 20) kev χ 2 /dof = 42.6/28 (upper tail probability 4%). The obtained χ 2 value is rather large due mainly to two data points, whose centroids are at and kev, far away from the (1 6) kev energy interval. The P-values obtained by excluding only the first and either the points are 11% and 25%.

23 S m for each annual cycle P = 5.2% P = 97% P = 25% P = 67% P = 72% DAMA/LIBRA-phase1 + DAMA/LIBRA-phase2 total exposure: 2.46 ton yr Energy bin (kev) run test probability Lower Upper % 70% % 73% % 35% % 30% % 30% The signal is well distributed over all the annual cycles in each energy bin

24 S m for each detector DAMA/LIBRA-phase1 + DAMA/LIBRA-phase2 total exposure: 2.17 ton yr S m integrated in the range (2-6) kev for each of the 25 detectors (1σ error) Shaded band = weighted averaged S m ± 1σ χ 2 /dof = 23.9/24 d.o.f. The signal is well distributed over all the 25 detectors.

25 External vs internal detectors: ΔE=0.5 kev external internal DAMA/LIBRA-phase2 Internal - External 1-4 kev χ 2 /dof =2.5/ kev χ 2 /dof =12.1/ kev χ 2 /dof =40.8/38

26 Is there a sinusoidal contribution in the signal? Phase day? [ ω( t t )] + Z sin ω( t t ) [ ] [ ( )] * = S + Y t R( t) = S ω t 0 + Sm cos 0 m 0 0 m cos For Dark Matter signals: Z m «S m Y m t * t 0 = 152.5d ω = 2π/T T = 1 year Slight differences from 2 nd June are expected in case of contributions from non thermalized DM components (as e.g. the SagDEG stream) DAMA/NaI + DAMA/LIBRA-phase1 + DAMA/LIBRA-phase2 [2.46 ton yr] E (kev) S m (cpd/kg/kev) Z m (cpd/kg/kev) Y m (cpd/kg/kev) t* (day) DAMA/NaI + DAMA/LIBRA-ph1 + DAMA/LIBRA-ph ± ± ± ± ± ± ± undefined DAMA/LIBRA-ph ± ± ± ± 5.0

27 [ ω( t t )] + Z sin ω( t t ) [ ] [ ( )] * = S + Y t R( t) = S ω t 0 + Sm cos 0 m 0 0 m cos 2σ contours DAMA/NaI + DAMA/LIBRAphase1 + DAMA/LIBRA-phase2 total exposure: 2.46 ton yr For Dark Matter induced signals: Z m «Y m S m t * t 0 = 152.5d ω = 2π/T T = 1 year Slight differences from 2 nd June are expected in case of contributions from non thermalized DM components (as the SagDEG stream)

28 R(t) = S 0 +Y m cos" # ω t t * ( ) Phase vs energy $ % DAMA/NaI + DAMA/LIBRA-phase1 + DAMA/LIBRA-phase2 (2.46 ton yr ) Y m, S m ΔE = 1 kev bins For DM signals: Y m S m t * t 0 = 152.5d ω = 2π/T; T = 1 year Slight differences from 2 nd June are expected in case of contributions from non thermalized DM components (as the SagDEG stream) 2σ errors

29 Stability parameters of DAMA/LIBRA phase2 Modulation amplitudes obtained by fitting the time behaviours of main running parameters, acquired with the production data, when including a DM-like modulation Running conditions stable at a level better than 1% also in the new running periods DAMA/LIBRAphase2_2 DAMA/LIBRAphase2_3 DAMA/LIBRAphase2_4 DAMA/LIBRAphase2_5 DAMA/LIBRAphase2_6 DAMA/LIBRAphase2_7 Temperature ( C) ( ± ) -( ± ) -( ± ) ( ± ) ( ± ) -( ± ) Flux N 2 (l/h) -(0.15 ± 0.18) -(0.02 ± 0.22) -(0.02 ± 0.12) -(0.02 ± 0.14) -(0.01 ± 0.10) -(0.01 ± 0.16) Pressure (mbar) (1.1 ± 0.9) 10-3 (0.2 ± 1.1) ) 10-3 (2.4 ± 5.4) 10-3 (0.6 ± 6.2) 10-3 (1.5 ± 6.3) 10-3 (7.2 ± 8.6) 10-3 Radon (Bq/m 3 ) (0.015 ± 0.034) -(0.002 ± 0.050) -(0.009 ± 0.028) -(0.044 ± 0.050) (0.082 ± 0.086) (0.06 ± 0.11) Hardware rate above single ph.e. (Hz) -(0.12 ± 0.16) 10-2 (0.00 ± 0.12) (0.14 ± 0.22) (0.05 ± 0.22) (0.06 ± 0.16) (0.08 ± 0.17) 10-2 All the measured amplitudes well compatible with zero + none can account for the observed effect (to mimic such signature, spurious effects and side reactions must not only be able to account for the whole observed modulation amplitude, but also simultaneously satisfy all the 6 requirements)

30 Can a possible thermal neutron modulation account for the observed effect? Thermal neutrons flux measured at LNGS : Φ n = n cm -2 s -1 (N.Cim.A101(1989)959) Experimental upper limit on the thermal neutrons flux surviving the neutron shield in DAMA/LIBRA: Ø studying triple coincidences able to give evidence for the possible presence of 24 Na from neutron activation: Φ n < n cm -2 s -1 (90%C.L.) 24m Na (T 1/2 =20ms) NO σ n = 0.43 barn σ n = 0.10 barn Two consistent upper limits on thermal neutron flux have been obtained with DAMA/NaI considering the same capture reactions and using different approaches. Evaluation of the expected effect: Capture rate = Φ n σ n N T < captures/day/kg HYPOTHESIS: assuming very cautiously a 10% thermal neutron modulation: S m (thermal n) < cpd/kg/kev (< 0.01% S m observed ) In all the cases of neutron captures ( 24 Na, 128 I,...) a possible thermal n modulation induces a variation in all the energy spectrum Already excluded also by R 90 analysis MC simulation of the process When Φ n = 10-6 n cm -2 s -1 : cpd/kg/kev cpd/kg/kev E (MeV)

31 No role for µ in DAMA annual modulation result ü Direct µ interaction in DAMA/LIBRA set-up: DAMA/LIBRA surface 0.13 m 2 µ DAMA/LIBRA 2.5 µ/day It cannot mimic the signature: already excluded by R 90, by multi-hits analysis + different phase, etc. ü Rate, R n, of fast neutrons produced by µ: Φ LNGS 20 µ m -2 d -1 (±1.5% modulated) Annual modulation amplitude at low energy due to µ modulation: S m (µ) = R n g ε f ΔE f single 2% /(M setup ΔE) Moreover, this modulation also induces a variation in other parts of the energy spectrum and in the multi-hits events MonteCarlo simulation S m (µ) < ( ) 10-5 cpd/kg/kev It cannot mimic the signature: already excluded by R 90, by multi-hits analysis + different phase, etc. ü Inconsistency of the phase between DAMA signal and µ modulation μ LNGS (MACRO, LVD, BOREXINO) m -2 s -1 ; modulation amplitude 1.5%; phase: July 7 ± 6 d, June 29 ± 6 d (Borexino) The DAMA phase: May 26 ± 7 days (stable over 13 years) The DAMA phase is 5.7σ far from the LVD/BOREXINO phases of muons (7.1 σ far from MACRO measured phase) many others arguments EPJC72(2012)2064, EPJC74(2014)3196

32 Contributions to the total neutron flux at LNGS; Counting rate in DAMA/LIBRA for single-hit events, in the (2 6) kev energy region induced by: Ø neutrons, Ø muons, Ø solar neutrinos. EPJC 74 (2014) 3196 (also EPJC 56 (2008) 333, EPJC 72 (2012) 2064,IJMPA 28 (2013) ) Modulation amplitudes The annual modulation of solar neutrino is due to the different Sun-Earth distance along the year; so the relative modulation amplitude is twice the eccentricity of the Earth orbit and the phase is given by the perihelion. All are negligible w.r.t. the annual modulation amplitude observed by DAMA/LIBRA and they cannot contribute to the observed modulation amplitude. + In no case neutrons (of whatever origin) can mimic the DM annual modulation signature since some of the peculiar requirements of the signature would fail, such as the neutrons would induce e.g. variations in all the energy spectrum, variation in the multiple hit events,... which were not observed.

33 Summary of the results obtained in the additional investigations of possible systematics or side reactions DAMA/LIBRA NIMA592(2008)297, EPJC56(2008)333, J. Phys. Conf. ser. 203(2010)012040, arxiv: , S.I.F.Atti Conf.103(211), Can. J. Phys. 89 (2011) 11, Phys.Proc.37(2012)1095, EPJC72(2012)2064, arxiv: & , IJMPA28(2013) , EPJC74(2014)3196, IJMPA31(2017)issue31 Source Main comment Cautious upper limit (90%C.L.) RADON Sealed Cu box in HP Nitrogen atmosphere, < 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 + intrinsic calibrations < 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 at LNGS < cpd/kg/kev + they cannot satisfy all the requirements of annual modulation signature Thus, they cannot mimic the observed annual modulation effect

34 Model-independent evidence by DAMA/NaI and DAMA/LIBRA-ph1, -ph2 well compatible with several candidates in many astrophysical, nuclear and particle physics scenarios

35 Model-independent evidence by DAMA/NaI and DAMA/LIBRA-ph1, -ph2 well compatible with several candidates in many astrophysical, nuclear and particle physics scenarios Just few examples of interpretation of the annual modulation in terms of candidate particles in some scenarios 50 GeV Evans logarithmic 15 GeV Isothermal sphere (channeling) 65 GeV Evans logarithmic 20 GeV Evans power law (channeling) LDM with coherent scattering on nuclei LDM with m L =0 GeV ( =m H )

36 Other scintillating detectors ANAIS. Project for 3 3 matrix of NaI(Tl) scintillators 12.5 kg each to study DM annual modulation at Canfranc (LSC). Several prototypes from different companies tested A 210 Pb contamination out-of-equilibrium is present in ANAIS-25 crystals. Origin of the 210 Pb contamination identified (crystal growing) and being solved by Alpha Spectra. New material prepared at Alpha Spectra using improved protocols Running: target mass of 112 kg DM-ICE. NaI(Tl) deployed at the South Pole KIMS. DM with CsI(Tl) crystals since 2000 at Yangyang (Y2L, Korea). More recently KIMS-NaI COSINE-100 =DM-ICE+KIMS Running since sept 2016: 100 kg NaI in Y2L Warning: PSD with CsI(Tl), NaI(Tl), sometimes overestimated sensitivity; high rejection power claimed; existing systematics limit the reachable sensitivity Key points: not only residual contaminants but also long-term/ high-level stability + SABRE (at the end of 2017), picolon, cryog. detectors At R&D stage to obtain competitive NaI(Tl) detectors wrt DAMA

37 Is it an universal and correct way to approach the problem of DM and comparisons? No, it isn t. This is just a largely arbitrary/partial/incorrect exercise

38 About interpretations and comparisons models Which particle? Which interaction coupling? Which Form Factors for each target-material? Which Spin Factor? Which nuclear model framework? Which scaling law? Which halo model, profile and related parameters? Streams?... See e.g.: Riv.N.Cim.26 n.1(2003)1, IJMPD13(2004)2127, EPJC47(2006)263, IJMPA21(2006)1445, EPJC56(2008)333, PRD84(2011)055014, IJMPA28(2013) and experimental aspects Exposures Energy threshold Detector response (phe/kev) Energy scale and energy resolution Calibrations Stability of all the operating conditions. Selections of detectors and of data. Subtraction/rejection procedures and stability in time of all the selected windows and related quantities Efficiencies Definition of fiducial volume and nonuniformity Quenching factors, channeling, Uncertainty in experimental parameters, as well as necessary assumptions on various related astrophysical, nuclear and particle-physics aspects, affect all the results at various extent, both in terms of exclusion plots and in terms of allowed regions/volumes. Thus comparisons with a fixed set of assumptions and parameters values are intrinsically strongly uncertain. No experiment can be directly compared in model independent way with DAMA

39 Examples of uncertainties in models and scenarios see for some details e.g.: Nature of the candidate and couplings WIMP class particles (neutrino, sneutrino, etc.): SI, SD, mixed SI&SD, preferred inelastic + e.m. contribution in the detection Light bosonic particles Kaluza-Klein particles Mirror dark matter Heavy Exotic candidate etc. etc. Scaling laws of cross sections for the case of recoiling nuclei Different scaling laws for different DM particle: σ A µ 2 A 2 (1+ε A ) Halo models & Astrophysical scenario Isothermal sphere very simple but unphysical halo model Many consistent halo models with different density and velocity distribution profiles can be considered with their own specific parameters (see e.g. PRD61(2000)023512) Caustic halo model Form Factors for the case of recoiling nuclei Many different profiles available in literature for each isotope Parameters to fix for the considered profiles ε A = 0 generally assumed Dependence on particlenucleus interaction ε A ±1 in some nuclei? even for neutralino candidate in In SD form factors: no MSSM (see Prezeau, decoupling between nuclear Kamionkowski, Vogel et al., and Dark Matter particles PRL91(2003)231301) degrees of freedom + dependence on nuclear potential Presence of nonthermalized DM particle components Streams due e.g. to satellite galaxies of the Milky Way (such as the Sagittarius Dwarf) Multi-component DM halo Clumpiness at small or large scale Solar Wakes etc. Spin Factors for the case of recoiling nuclei Calculations in different models give very different values also for the same isotope Depend on the nuclear potential models Large differences in the measured counting rate can be expected using: either SD not-sensitive isotopes Riv.N.Cim.26 n.1 (2003) 1, IJMPD13(2004)2127, EPJC47 (2006)263, IJMPA21 (2006)1445 Instrumental quantities Energy resolution Efficiencies Quenching factors Channeling effects Their dependence on energy Quenching Factor differences are present in different experimental determinations of q for the same nuclei in the same kind of detector depending on its specific features (e.g. q depends on dopant and on the impurities; in liquid noble gas e.g.on trace impurities, on presence of degassing/ releasing materials, on thermodynamical conditions, on possibly applied electric field, etc); assumed 1 in bolometers or SD sensitive isotopes channeling effects possible depending on the unpaired increase at low energy in nucleon (compare e.g. odd spin scintillators (dl/dx) isotopes of Xe, Te, Ge, Si, W with possible larger values of q the 23 Na and 127 I cases). (AstropPhys33 (2010) 40) and more energy dependence

40 DMp case of DM particles inducing elastic scatterings on target-nuclei, SI case N DAMA allowed regions for a particular set of astrophysical, nuclear and particle Physics assumptions without (green), with (blue) channeling, with energydependent Quenching Factors (red); 7.5 C.L. DMp example Regions in the nucleon cross section vs DM particle mass plane Some velocity distributions and uncertainties considered. The DAMA regions represent the domain where the likelihood-function values differ more than 7.5σ from the null hypothesis (absence of modulation). For CoGeNT a fixed value for the Ge quenching factor and a Helm form factor with fixed parameters are assumed. The CoGeNT region includes configurations whose likelihood-function values differ more than 1.64σ from the null hypothesis (absence of modulation). This corresponds roughly to 90% C.L. far from zero signal. Including the Migdal effect àtowards lower mass/higher σ PRD84(2011)055014, IJMPA28(2013) Co-rotating halo, Non thermalized component à Enlarge allowed region towards larger mass CoGeNT; qf at fixed assumed value 1.64 C.L. Combining channeling and energy dependence of q.f. (AstrPhys33 (2010) 40) àtowards lower σ

41 Scratching Below the Surface of the Most General Parameter Space (S. Scopel arxiv: ) Most general approach: consider ALL possible NR couplings, including those depending on velocity and momentum A much wider parameter space opens up First explorations show that indeed large rooms for compatibility can be achieved and much more considering experimental and theoretical uncertainties Other examples DMp with preferred inelastic interaction: χ - + N χ + + N idm mass states χ +, χ - with δ mass splitting Kinematic constraint for idm: 1 2 µv2 δ v v thr = 2δ µ idm interaction on Tl nuclei of the NaI(Tl) dopant? PRL106(2011) For large splittings, the dominant scattering in NaI(Tl) can occur off of Thallium nuclei, with A~205, which are present as a dopant at the 10-3 level in NaI(Tl) crystals. large splittings do not give rise to sizeable contribution on Na, I, Ge, Xe, Ca, O, nuclei. Mirror Dark Matter DAMA/NaI+DAMA/LIBRA Slices from the 3d allowed volume in given scenario Fund. Phys. 40(2010)900 Asymmetric mirror matter: mirror parity spontaneously broken mirror sector becomes a heavier and deformed copy of ordinary sector (See EPJC75(2015)400) Interaction portal: photon - mirror photon kinetic mixing mirror atom scattering of the ordinary target nuclei in the NaI(Tl) detectors of DAMA/LIBRA set-up with the Rutherford-like cross sections. coupling const. and fraction of mirror atom DAMA/LIBRA allowed values for f in the case of mirror hydrogen atom, Z = 1

42 Perspectives for the future Other signatures? Diurnal effects Second order effects Shadow effects Directionality

43 Model independent result on possible diurnal effect in DAMA/LIBRA phase1 2-4 kev 2-4 kev Eur. Phys. J. C 74 (2014) 2827 solar 2-5 kev 2-5 kev sidereal Experimental single-hit residuals rate vs either sidereal and solar time and vs energy. These residual rates are calculated from the measured rate of the single-hit events after subtracting the constant part solar kev solar kev sidereal sidereal 6-14 kev Energy region where the annual modulation is observed. Energy region just above. solar sidereal no diurnal variation with a significance of 95% C.L. + run test to verify the hypothesis that the positive and negative data points are randomly distributed. The lower tail probabilities (in the four energy regions) are: 43, 18, 7, 26% for the solar case and 54, 84, 78, 16% for the sidereal case. Thus, the presence of any significant diurnal variation and of time structures can be excluded at the reached level of sensitivity.

44 A diurnal effect with the sidereal time is expected for DM because of Earth rotation Velocity of the detector in the terrestrial laboratory: Eur. Phys. J. C 74 (2014) 2827 Since: at LNGS velocity of the Local Standard of Rest (LSR) due to the rotation of the Galaxy Sun peculiar velocity with respect to LSR velocity of the revolution of the Earth around the Sun velocity of the rotation of the Earth around its axis at the latitude and longitude of the laboratory. Annual modulation term: V Earth is the orbital velocity of the Earth 30 km/s B m t 0 t equinox days June 2 Diurnal modulation term: V r is the rotational velocity of the Earth at the given latitude (for LNGS km/s) B d t d h (at LNGS) Velocity of the Earth in the galactic frame as a function of the sidereal time, with starting point March 21 (around spring equinox). The contribution of diurnal rotation has been dropped off. The maximum of the velocity (vertical line) is about 73 days after the spring equinox. Sum of the Sun velocity in the galactic frame (v s ) and of the rotation velocity of a detector at LNGS (v s v rot (t)) as a function of the sidereal time. The maximum of the velocity is about at 14 h (vertical line).

45 Investigating diurnal modulation in DAMA/LIBRA-phase1 Expected modulation amplitude Annual modulation amplitude: Diurnal modulation amplitude: EPJC74(2014)2827 The ratio R dy of the diurnal over annual modulation amplitudes is a model independent constant Annual modulation amplitude in DAMA/ LIBRA phase1 in the (2 6) kev: ( ± ) cpd/kg/kev Expected value of diurnal modulation amplitude: LNGS sidereal time A d random fluctuations around zero: χ 2 =19.5/18 dof Fitting the single-hit residuals with a cosine function with amplitude A d as free parameter, period 24 h and phase 14 h A d (2-6 kev) < cpd/kg/kev (90%CL) Present experimental sensitivity lower than the diurnal modulation amplitude expected from the DAMA/LIBRA phase1 observed effect. Larger exposure DAMA/LIBRA phase2 (+ lower energy threshold) offers increased sensitivity

46 Perspectives for the future Other signatures? Diurnal effects Second order effects Shadow effects Directionality

47 Earth shadowing effect with DAMA/LIBRA phase1 EPJC75(2015)239 Earth Shadow Effect could be expected for DM candidate particles inducing nuclear recoils can be pointed out only for candidates with high crosssection with ordinary matter (low DM local density) would be induced by the variation during the day of the Earth thickness crossed by the DM particle in order to reach the experimental set-up DM particles crossing Earth lose their energy DM velocity distribution observed in the laboratory frame is modified as function of time (GMST 8:00 black; GMST 20:00 red) Taking into account the DAMA/LIBRA DM annual modulation result, allowed regions in the vs n plane for each m DM.

48 Perspectives for the future Other signatures? Diurnal effects Second order effects Shadow effects Directionality

49 Running phase2 and towards future DAMA/LIBRA phase3 with software energy threshold below 1 kev Enhancing sensitivities for DM corollary aspects, other DM features, second order effects and other rare processes: The light collection of the detectors can further be improved Light yields and the energy thresholds will improve accordingly The electronics can be improved too R&D towards possible DAMA/LIBRA-phase3 continuing: 1 new development of high Q.E. PMTs with increased radio-purity to directly couple them to the crystals. 2 new protocols for possible modifications of the detectors; 3 alternative strategies under investigation. 4 Other possible option: new ULB crystal scintillators (e.g. ZnWO 4 ) placed in between the DAMA/LIBRA detectors to add also a high sensitivity directionality measurement. The presently-reached metallic PMTs features: Q.E. around 420 nm (NaI(Tl) light) Radio-purity at level of 5 mbq/pmt ( 40 K), 3-4 mbq/pmt ( 232 Th), 3-4 mbq/pmt ( 238 U), 1 mbq/pmt ( 226 Ra), 2 mbq/pmt ( 60 Co). 4 prototypes from a dedicated R&D with HAMAMATSU at hand

50 The importance of studying second order effects and the annual modulation phase DAMA/NaI+LIBRA-phase1 High exposure and lower energy threshold can allow further investigation on: - the nature of the DM candidates - possible diurnal effects on the sidereal time - astrophysical models The annual modulation phase depends on : Presence of streams (as SagDEG and Canis Major) in the Galaxy Presence of caustics Effects of gravitational focusing of the Sun PRL112(2014) Features of the DM signal A step towards such investigations: èdama/libra-phase2 running with lower energy threshold and larger exposure + further possible improvements (DAMA/LIBRA-phase3) and DAMA/1ton

51 Perspectives for the future Other signatures? Diurnal effects Second order effects Shadow effects Directionality

52 Directionality technique (at R&D stage) Only for candidates inducing just recoils Identification of the Dark Matter particle by exploiting the non-isotropic recoil distribution correlated to the Earth position with to the Sun NEWAGE Anisotropic scintillators: DAMA, UK, Japan DRIFT-IId Background dominated by Radon Progeny Recoils (decay of 222 Rn daughter nuclei, present in the chamber) Nano Imaging Tracker (NIT) emulsions Track readout: track length ranges also. è use different optical technique and make a pre-selection on the optical microscopes -PIC(Micro Pixel Chamber) is a two dimensional position sensitive gaseous detector DM-TPC The 4-- Shooter 18L (6.6 gm) TPC 4xCCD, Sealevel@MIT moving to WIPP Cubic meter funded, design underway Not yet competitive sensitivity

53 Directionality technique with crystals Only for candidates inducing just recoils EPJ C73 (2013) 2276 Identification of the Dark Matter particles by exploiting the non-isotropic recoil distribution correlated to the Earth velocity The use of anisotropic scintillators was proposed by DAMA (N.Cim.C15(1992)475, EPJC28(2003)203); then UK, Japan preliminary activities The ADAMO project: Study of the directionality approach with ZnWO 4 anisotropic detectors Nuclear recoils are expected to be strongly correlated with the DM impinging direction This effect can be pointed out through the study of the variation in the response of anisotropic scintillation detectors during sidereal day σ p = pb, m DM = 50 GeV [2-3] kev The light output and pulse shape of ZnWO 4 depend on the direction of the impinging particles with respect to the crystal axes Both these anisotropic features can provide two independent ways to exploit the directionality approach These and others competitive characteristics of ZnWO 4 detectors could permit to reach sensitivity comparable with that of the DAMA/LIBRA positive result Example (for a given model framework) of the expected counting rate as a function of the detector velocity direction

54 Other techniques DAMIC at SNOLAB Charge coupled devices (CCDs) as detectors for low-energy particles Background suppression techniques Ongoing R&D efforts for a DAMIC-1K: 1 kg detector, 50 CCDs with 2e - thr. NEWS-G, a spherical TPC with low-a target Sensitive to low mass DM candidate

55 Other techniques PICO: bubble chamber, using acoustic discrimination, C 3 F 8 target Acoustic discrimination Now: PICO-60 Next step PICO 500 Alphas deposit their energy over tens of microns Nuclear recoils deposit theirs over tens of nanometers Bubble Chamber Geyser In both cases: technical limitations on the technique (reachable sensitivities, energy thresholds, stability, ), only DM candidates inducing recoils, tests made at very high energy recoils, what about low energy recoils?

56 Conclusions Model-independent positive evidence for the presence of DM particles in the galactic halo at 12.9σ C.L. (20 independent annual cycles with 3 different set-ups: 2.46 ton yr) Modulation parameters determined with increasing precision New investigations on different peculiarities of the DM signal exploited in progress Full sensitivity to many kinds of DM candidates and interactions types (both inducing recoils and/or e.m. radiation), full sensitivity to low and high mass candidates DAMA/LIBRA phase2 continuing data taking DAMA/LIBRA phase3 R&D in progress R&D for a possible DAMA/1ton - full sensitive mass - set-up, proposed to INFN by DAMA since 1996, continuing at some extent as well as some other R&Ds New corollary analyses in progress Continuing investigations of rare processes other than DM