Results on dark matter annual modulation from ANAIS-112 experiment J. Amaré, S. Cebrián, D. Cintas, I. Coarasa, E. García, M. Martínez, M.A. Oliván, Y. Ortigoza, A. Ortiz de Solórzano, J. Puimedón, A. Salinas, M.L. Sarsa , P . Villar UNIVERSIDAD DE ZARAGOZA 11 September 2019
Annual modulation with NAI Scintillators ANAIS experiment 80 800 m rock • Confirmation of DAMA-LIBRA modulation signal -> same target and technique / different experimental approach / different environmental conditions affecting systematics • At Canfranc Underground Laboratory, @ SPAIN (under 2450 m.w.e. ) taking data since August 2017 • 3x3 matrix of 12.5 kg NaI(Tl) cylindrical modules = 112.5 kg of active mass
Annual modulation with ANAIS-112 Experimental Strategy NAI Scintillators EXPERIMENTAL GOALS • Maximizing exposure (mass x time) • Stable operation • Data blinding • Low energy threshold (1keVee) Low noise DAQ system / excellent light collection / good energy calibration down to 1keV / efficient PMT noise events filtering • Low background @ 1-6 keV Radiopure detectors / Convenient shielding (including muon veto) / efficient PMT noise events filtering /
The ANAIS-112 first year general performance -> Eur. Phys. J. C 79 (2019) 228 The ANAIS-112 background model -> Eur. Phys. J. C 70 (2019) 412 10% first year unblinded (randomly chosen days) The ANAIS-112 sensitivityprospects -> Eur. Phys. J. C 70 (2019) 233 OUTLINE ANAIS-112 first results-> Phys. Rev. Lett. 123 (2019) 031301
• 12.5 kg cylindrical NaI(Tl) detectors built @ • Alpha Spectra, Co (US) ANAIS detectors and shielding • 40 K / 210 Pb @ NaI(Tl) • Optical quality • 2 x HQE PMTs Ham12669SEL2 coupled at LSC clean room • Installed at LSC in a convenient shielding
Mylar window for energy calibration ANAIS-112 calibration system 109 Cd sources on flexible wires in a Radon free system which allows the simultaneous calibration of the 9 modules Energies 11.9 keV / 22.6 keV / 88.0 keV Every two weeks
• DAQ hardware and software designed and tested with previous set-ups -> ROBUST • Individual PMT signals digitized and fully processed (14 bits / 2GS/s) • Trigger at phe level for each PMT • Logical AND coincidence in 200ns window for each module triggering • Redundant energy conversion (with QDCs for HE) ANAIS-112 DAQ
• DAQ hardware and software designed and tested with previous set-ups -> ROBUST • Individual PMT signals digitized and fully processed (14 bits / 2GS/s) • Trigger at phe level for each PMT • Logical AND coincidence in 200ns window for each module triggering • Redundant energy conversion (with QDCs for HE) ANAIS-112 DAQ • Electronics at air-conditioned-room to decouple from temperature fluctuations
The ANAIS-112 Dark Matter Run started on August 3, 2017 Accumulated live time in the first year: 341.72 days in the half second year: 185.36 days ANAIS-112 Duty Cycle ___________________________ total:527.08 days 2 nd year (until Feb19) 1 st year
The ANAIS-112 Dark Matter Run started on August 3, 2017 Accumulated live time in the first year: 341.72 days in the half second year: 374.30 days ANAIS-112 Duty Cycle ___________________________ total:716.02 days 2 nd year 1 st year
ANAIS-112 Low Energy Calibration Periodic 109 Cd calibrations They allow monitoring (and if necessary correcting) possible gain drifts in the modules. Done every 2 weeks PMT HV bias changed Evolution of the positions of 109 Cd lines along ANAIS-112. All the modules, except D4 and D5, have been very stable during this period of data taking. 88.0 keV 22.6 keV 11.9 keV
Excellent light collection ANAIS-112 Light Collection M.A. Oliván et al, Astropart. Phys. 93 (2017) 86 DAMA/LIBRA: Larger and more homogeneousthan Phase 1: 5.5-7.5 phe/keV the light collectionforDAMA/LIBRA –phase 2 detectors Phase 2: 6-10 phe/keV JINST 7 (2012) 03009 Being continuouslymonitored
Muon rates onsite are being monitored along the ANAIS-112 DM run. ANAIS-112 Monitoring of muons Muon related events are triggering ANAIS Total Trigger rate after DAQ trigger rate filtering 1 s after a muon veto trigger Most of them are removed by rejecting 1 second after a veto trigger The fraction of live time 70 s rejected after the application of this filtering amounts only to a 3%.
ANAIS-112 Data Analysis
Calibration @ HE (above 50 keV) we estimate energy by linearizing the pulse area – QDC relation for each module ANAIS-112 HE /LE calibration and calibratingwith backgroundlines(every two weeks) Effectively triggering below 1 keV Bulk 22 Na and 40 K events identifiedby coincidences with highenergy gammas Populationsat very LE well tagged by the coincidence 0.87 keV from 22 Na is actually below our analysis threshold, but clearly above our trigger threshold Selection by the coincidence allows to use these events (almost free from noise/background) Calibration at LE combines 109 Cd lines with 22 Na and 40 K (every 1.5 months)
Full First Year Data selected by coincidence with a HE gamma 40 K 22 Na ANAIS-112 HE /LE calibration Fitted to a Gaussian + linear bckg Allows checking the energy calibration procedure in the RoI Calibration at LE combines 109 Cd lines with 22 Na and 40 K (every 1.5 months)
- Single Hit events - Events arriving more than 1 second after a muon Live Time (after cut) = 511.16 days ANAIS-112 Event Selection
- Single Hit events - Events arriving more than 1 second after a muon Live Time (after cut) = 511.16 days ANAIS-112 Event Selection PMT noisefilteringprotocols: - Biparametric cut to properly select events with pulse shapes from NaI(Tl) scintillation 10 % data unblinded Efficiency calculated background @ RoI from 22 Na and 40 K (random distribution) events
- Single Hit events - Events arriving more than 1 second after a muon Live Time (after cut) = 511.16 days ANAIS-112 Event Selection PMT noisefilteringprotocols: - Biparametric cut to properly select - Asymmetric events rejection events with pulse shapes from NaI(Tl) (E<2keV), number of peaks >4 at scintillation each PMT BKG CAL Efficiency calculated from calibration events
ANAIS-112 Event Selection efficiency ANALYSIS THRESHOLD @ 1 keV
ANAIS-112 Event Selection Raw data below 10 keV 10 % data unblinded background @ RoI (random distribution)
ANAIS-112 Event Selection - Biparametric cut to properly select events with pulse shapes from NaI(Tl) scintillation 10 % data unblinded background @ RoI (random distribution)
ANAIS-112 Event Selection - Asymmetric events rejection (E<2keV), number of peaks >4 at each PMT 10 % data unblinded background @ RoI (random distribution)
- Events arriving more ANAIS-112 Event Selection than 1 second after a muon - Single Hit events 1 keV ee 10 % data unblinded background @ RoI (random distribution)
Detailed background models based on Geant4 Monte Carlo simulation ANAIS-112 Background Model and accurate quantification of background sources Internal activity directlyassessed by different techniques: 40 K, 210 Pb, natural chains Activity from external components measured with HPGe detectors, mainlythe PMTs Cosmogenic activity in crystals( 22 Na, short lifeI and Te isotopes, Tritium, 109 Cd, 113 Sn, etc.) JCAP 02 (2015) 046 Astropart. Phys. 97 (2018) 96 Int. J. Mod. Phys. A 33 (2018) 1843006 40 K and 22 Na peaks and 210 Pb (bulk+surface) and 3 H continua are the most significant contributions in the very low energy region
Overall description of measured data at all energy ranges above 2 keV in coincidence and anticoincidence is good ANAIS-112 Background Model HE total spectra About 5% average deviation between simulationand measurement
Overall description of measured data at all energy ranges above 2 keV in coincidence and anticoincidence is good ANAIS-112 Background Model HE concidence spectra About 3% average deviationbetween simulationand measurement
Overall description of measured data at all energy ranges above 2 keV in coincidence and anticoincidence is good ANAIS-112 Background Model LE anticoincidence spectra For the 10% unblindeddata About 8% average deviationbetween simulationand measurement @ 2-6 keV
• Good agreement at low ANAIS-112 Background Model energy (<100 keV) • At very low energy (<20 keV) (Commissioning July 2017) Most significantcontributions: • 40 K and 22 Na peaks • 210 Pb (bulk+surface) • 3 H Below 2 keVthe background model does not explain the measurement in about a 50%.
arXiv:1903.03973
Backgrounddecayrate in the RoI consistentwith our backgroundmodel ANAIS-112 annual modulation (in green) vs constant+ exponentialfit (in red)
Evolution of “control populations” consistentwith the absence of modulation ANAIS-112 annual modulation 22 Na events (0-2 keV) 40 K events (2-5 keV) M2 events in the RoI (1-6 keV) M1 events above the RoI (6-20 keV)
Least squared fit of the ANAIS-112 time-binned data in 1-6 / 2-6 keV energy regions to: ANAIS-112 annual modulation τ is fixed from background model ω is fixed (1 year period) φ is fixed to have the maximum of the cosine function in June, 2 nd S m is fixed to 0 to analyze the null hypothesis and left unconstrained for the modulation hypothesis DAMA/LIBRA result with 1 –free parameter is shown for comparison
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