DarkSide new results and prospects Stefano Davini - INFN Genova on behalf of the DarkSide collaboration La Thuile, March 20, 2018
The DarkSide WIMP-argon program at LNGS 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 Past Present Future DS-10 DS-50 DS-20k technical prototype dark matter runs ongoing σ (χn) ~ 10-44 cm 2 @ WIMP mass 100 GeV/c 2 σ (χn) ~ 10-41 cm 2 @ WIMP mass 2 GeV/c 2 projected sensitivity σ (χn) ~ 10-48 cm 2 @ WIMP mass 100 GeV/c 2
The DarkSide-50 detector cosmic-ray veto 1 kton Water Cherenkov neutron veto 30 ton Borated Liquid Scint dark matter detector Time Projection Chamber 50 kg Liquid Argon from underground source low in radioactive 39 Ar
The DarkSide-50 signals S1 primary scintillation signal collected by 38 PMTs S1 Powerful Pulse Shape allows to discriminate between - nuclear recoils (WIMP, neutrons) - electron recoils (β-γ backgrounds) 4
The DarkSide-50 signals Nuclear recoil Nuclear Recoil (WIMP signals) β/γ Beta/Gamma (backgrounds) S1 S1 f 90 1 0.9 Energy [kev nr ] 20 40 60 80 100 120 140 160 180 200 7 Li(p,n) in SCENE 241 AmBe in DarkSide-50 S1 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Nuclear recoils β/γ 50 100 150 200 250 300 350 400 450 S1 [PE]
The DarkSide-50 signals! e - e - e - e - e - e - e - e - S2 drift time S2 secondary electroluminescence signal one extracted e - -> S2~23 PE in central PMT allows for lower threshold analysis S2-S1 drift time -> vertical position S2 pattern on top PMTs -> horizontal position S1 & S2 -> 3D position reco S1 top S2 S2 S1 6
WIMP search - A blind analysis WIMP blind box DON T LOOK HERE! 7
WIMP search - A blind analysis f 90 f 90 1 no cuts - previous 71 days search data - PRD 93 (2016) 081101 5 10 0.8 WIMP BLIND BOX (final choose) 4 10 0.6 test regions 3 10 0.4 2 10 0.2 10 0 0 100 200 300 400 500 600 Goal - design WIMP analysis with < 0.1 background in box S1 [PE] Using test regions to test bkg model prior to unblinding S1 [PE] 1
WIMP search - 532 days Energy [kev nr ] 0 1 20 40 60 80 100 120 140 160 180 200 0.9 500 f 90 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 1% 50% 99% 400 300 200 100 0 0 50 100 150 200 250 300 350 400 450 S1 [PE] 0 arxiv: 1802.07198
WIMP search - 532 days 3.4 10 %&. () * @10 TeV/( * 1.1 10 %&& () * @100 GeV/( * 3.8 10 %&& () * @1 TeV/( * WIMP-nucleon Spin Indep. STD Halo Model 90% C.L. exclusion plot arxiv: 1802.07198
Low mass WIMP search e - S2! " = $% 2* +( %, % 50 123 2' ( ' ( ' 67 ( ~37 GeV For ' + = 10 GeV! " ~1.4 KeV ' + 100 523 χ % 100 523 ' ( Nuclear recoils from low mass WIMP detectable in S2 (charge yield ~6 e - /kevnr, electrolum. yield ~23 PE/e - ) but not detectable in S1 (light yield ~2 PE/keVnr) S2-only low mass WIMP search Below threshold for S1 production (~ 6 123 D7 ) but S2 has threshold ~ 0.4 123 D7 arxiv: 1802.06994
Low mass WIMP search arxiv: 1802.06994
Low mass WIMP search binomial fluctuation no quenching fluctuation DarkSide-50 arxiv: 1802.06994
Light DM on electron! " = $ & ' $) 2+,- ~ 1 2 12 4, 512 For 4, = 100 MeV! " ~50 ev Use lightness of electron to investigate light mass DM! " #$ 16.08 ev,!" #, 34.76 ev,! " 0$ 260.45 ev,!" 0, 335.30 ev,! " 3, 3227.51 ev Recoil energy comparable with binding energies in argon atoms e - S2 Same S2-only analysis but very different interpretation χ arxiv: 1802.06998
LDM on electron - scattering rate min. velocity for Eer in bounded electrons ionization form factor LDM form factor! "# $ % = 1: heavy mediator! "# $ % 1 $ % : light mediator arxiv: 1802.06998
LDM on electron - DS-50 constraints! "# $ % = 1: heavy mediator! "# $ % 1 $ % : light mediator arxiv: 1802.06998
The Future DS-20k GADMC
DarkSide - Outlook DarkSide-50 at LNGS: a successful 3-year underground argon run lead to new dark matter constraints DarkSide-50 532 day Dark Matter Search with Low-Radioactivity Argon 1802.07198 Low-mass Dark Matter Search with the DarkSide-50 experiment 1802.06694 Constraints on sub-gev Dark Matter Electron Scattering from the DarkSide-50 experiment 1802.06998 DarkSide-20k and GADMC, the next tyrants in the dark matter argon community
Backup Slides
s] 10 1 atmospheric and underground argon at 200 V/cm kg Events / [80 PE 2 10 3 10 10 4 5 10 < 1/300 < 1/1000 AAr (200 V/cm, LSV anti-coinc.) UAr (200 V/cm, LSV anti-coinc.) 39 Ar (from global fit) 85 Kr (from global fit) 6 10 10 7 39Ar in UAr < 1 mbq/kg 85Kr in UAr ~ 2 mbq/kg 8 10 0 1000 2000 3000 4000 5000 6000 S1 [PE]
DarkSide-50 γ-rays
DarkSide-50 alphas 1.8 1.6 3 10 Energy [MeV] 4 4.5 5 5.5 6 6.5 Data Events / [250 PE] 1.4 1.2 1 0.8 0.6 Degraded: Under TPB 210 Po 222 Rn 218 Po Full-energy: In LAr 0.4 0.2 0 30 35 40 45 S1 [PE] many with small or no S2, surface decays in TPB (wavelength shifter) additional rejection because of long light emission tail 3 1000 10
DarkSide-50 neutrons n + 10 B a + 7 Li n + 10 B a + 7 Li* + g neutron veto, calibration with 241Am13C source efficiency 0.9964 +- 0.0004 for LAr TPC single site nuclear recoils
DarkSide-50 backgrounds 350 14 Drift time [µs] 300 250 200 150 100 50 0 2 4 6 8 10 12 14 16 18 20 Reconstructed radius [cm] 12 10 8 6 4 2 0 Background Est. Survive Surface α decays 1 Cosmogenic n <0.0003 Radiogenic n <0.005 ER S1+Cherenkov 0.08* Total 0.09±0.04 10 4 Single-Scatter Unresolved Multi-Scatter 0.85 Scintillation + Fused-Silica Cherenkov Events / [0.01 f90] 3 10 10 2 10 1 1 10 Scintillation + PTFE Cherenkov f 90 0.8 0.75 0.7 0.65 Radiogenic Cosmogenic Fission candidate 50% NR acceptance 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 f90 100 150 200 250 300 350 400 450 S1 [PE]
DarkSide-50 electron recoil charge yield Events/[0.05 Ne kg day] 37 Ar 37 Ar 0.27 kev 37 Ar 2.8 kev Ne=47.9 N e
Argon and Xenon charge yield Q y [e /kev nr ] e (Lindhard reduced energy)
DarkSide-50 single electron spectrum Events/[0.05 N e kg day] N e
DarkSide-50 S2-based analysis acceptance Acceptance Fiducialization Trigger efficiency S2 Identification (f 90 < 0.15) S2 [PE]