direct detection - cern indico
TRANSCRIPT
M. Schumann (Freiburg) – Dark Matter 1
Direct DetectionStatus and Prospects of mid- to high-mass WIMP searches
Marc Schumann U Freiburg
ZPW 2019 „A new look to dark mattter“ Zurich, January 09, 2019
M. Schumann (Freiburg) – Direct Detection 3
Direct WIMP Search
Nuclear RecoilER ~ O(10 keVnr)
WIMP
WIMP
v ~ 230 km/s
Elastic Scattering of WIMPs off target nuclei nuclear recoil
Detectable Signal
Electronic Recoil
A²
form factor
XenonGermanium
ArgonSilicon
m=100 GeV/c² = 1x10–47 cm²
χ χ
ƒ ƒ
10–1
Rat
e [e
vent
s/(t
y k
eV)]
10–2
10–1
10–3
RecoilSpectra:
M. Schumann (Freiburg) – Direct Detection 4
Direct WIMP Search
Nuclear RecoilER ~ O(10 keVnr)
WIMP
WIMP
v ~ 230 km/s
Elastic Scattering of WIMPs off target nuclei nuclear recoil
Detectable Signal
Electronic Recoil
A²
form factor
XenonGermanium
ArgonSilicon
m=100 GeV/c² = 1x10–47 cm²
χ χ
ƒ ƒ
10–1
Rat
e [e
vent
s/(t
y k
eV)]
10–2
10–1
10–3
tiny!
tiny! low mass → low threshold
RecoilSpectra:
M. Schumann (Freiburg) – Direct Detection 6
Current Status
spin-independent WIMP-nucleon interactions
some results are missing...
M. Schumann (Freiburg) – Direct Detection 7
Current Status
spin-independent WIMP-nucleon interactions
some results are missing...
Low-mass WIMPs→ see talk by Federica
0.1 0.5 4000
M. Schumann (Freiburg) – Direct Detection 8
DAMA/LIBRA: New Resultsspin-independent WIMP-nucleon interactions
11.9σ CL
DAMA/LIBRA: Universe 4 (2018) 116
Phase 1Phase 2
~250 kg NaI(Tl)
New data: – 1 keVee threshold– 6 annual cycles
M. Schumann (Freiburg) – Direct Detection 9
DAMA/LIBRA: New Resultsspin-independent WIMP-nucleon interactions
Phase 1Phase 2
I
Na
Phys.Lett. B789 (2019) 262
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Exclusion by COSINE-100
COSINE-100– 106 kg of NaI(Tl)– 2000L liquid scint. veto → suppress 40K bckgnd– BUT: low-E background still 3x DAMA/LIBRA– no excess above background in 60 day run
Nature 564 (2018) 83
DAMA signal
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Exclusion by COSINE-100
COSINE-100– 106 kg of NaI(Tl)– 2000L liquid scint. veto → suppress 40K bckgnd– BUT: low-E background still 3x DAMA/LIBRA– no excess above background in 60 day run4,
99 c
m
DM-nucleon scattering excluded by 5 orders of magnitude!
Nature 564 (2018) 83
DAMA signal
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Annual Modulation Searches
– dark matter–electron scattering
– 2-phase LXe TPCs operated stably over long periods
XENON100: 4 yearsLUX: 2 years
– challenges DAMA/LIBRAXENON100: 5.7σLUX: 9.2σ
XENON100: PRL 118, 101101 (2017)
LUX: PRD 98, 062005 (2018)
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Current Status
spin-independent WIMP-nucleon interactions
liquid noble gas TPCs:best results above ~1.8 GeV/c²
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TPC = time projection chamber
Dual-Phase TPC
Time
Am
plitu
de
S2 – Charge→ proportional scintillation
neg HVE~0.5 kV/cm
pos HVE~10 kV/cm
TimeA
mpl
itude
Time
Am
plitu
de
S1 – Light
Dark Matter WIMP= single scatter nuclear recoil
Background (β, γ)
Background (neutron)
● 3d position reconstruction → target fiducialization
● background rejection
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Electronic Recoils Nuclear Recoils(gamma, beta) (neutron, WIMPs)
muons
natural γ-bg
neutrons from(α,n) and sf
target-intrinsic bg:β-radiation;activation, impurities,2νββ
neutrons from(α,n) and sf
muon-inducedneutrons
natural γ-bg
pp+7Be neutrinos→ ER signature
high-E neutrinos→ CNNS bg→ NR signature
Background Sources
natural γ-bg
neutrons from(α,n) and sf
muons
muon-inducedneutrons
(for ton-scale detectors)
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ER Background Rejection
PR
L 107, 131
302 (2011)
ER
NR
Nuclear Recoils
Electronic Recoils
Astropart. Phys. 85, 23 (2016)Pulse shape discrimination (PSD):Lifetimes of singlet and triplet states:
Ar: 5 ns, 1.6 µsXe: 4 ns, 22 ns
Ratio Ntrip/Nsing depends on dE/dx→ the interaction type
LAr: excellent ~3×10–8
PRC 78, 035801 (2008)
LXe: irrelevant ~1×10–1
NIM A 612, 328 (2010), arXiv:1803.07935
Charge-Light-Ratio (S2/S1):Signal partition in light/charge depends → works for LXe and LAr (2-phase)on dE/dx → the interaction type → significant loss of acceptance
Edrift [kV/cm] LY @ 122 keV[PE/keV]
NR acc[%]
ER rej[%]
XENON100 0.53 3.8 40 2.5×10–3
XENON100 0.53 3.8 30 1×10–3
LUX 0.18 8.8 50 1..10×10–3
ZEPLIN-III 3.4 4.2 50 1.3×10–4
K. Ni APP14 0.2-0.7 10 50 <1×10–4
high thresholdrequired
works down tolow-E threshold
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<5 GeV/c²: DarkSide-50PRL 121 (2018) 081307
Charge-only Analysis
– no light signal (S1) required → reduce threshold → give up z-fiducialization, ER rejection via PSD, S2/S1
– depleted Ar target (46 kg) 39Ar reduced by >3 orders of magnitude– exposure 0.02 t×y threshold: 0.1 keVee– background:
1.5 kg–1d–1keV–1 = 5.5 × 105 t–1y–1keV–1 – background understood down to ~7 electrons (~1.2 keVnr)
→ no excess observed
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>5 GeV/c²: XENON1T
→ ER background: 85 t–1y–1keV–1
→ no statistically significant excess observed in 1t×y
200 GeV/c²
largest LXe TPC ever built cylinder: 96 cm active LXe target: 2.0t (3.2t total)
248 PMTs
PRL 121 (2018) 111302
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Status Spin-Dependent Couplings● coupling of WIMP to unpaired nucleon spins
● traditionally separated in proton-only and neutron-only
● same parameter space explored by indirect and collider searches
WIMP-proton WIMP-neutron
*XENON1T curves estimated by scaling SI-result
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PICO-60– 52 kg bubble chamber filled with C
3F
8
(„octafluoropropane“)– threshold detector– „immune“ to gamma/beta radiation– acoustic rejection of alphas
– 1167 kg×d exposure (efficiency corrected) = 3.2 × 10–3 t × y– 3.3 keVnr threshold
→ no excess observed
PICO-500 with 500L C3F
8 chamber
willl be built at SNOLAB
PRL 118 (2017) 251301
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Upcoming Projects
some results are missing...
Low-mass WIMPs→ see talk by Federica
0.1 0.5
spin-independent WIMP-nucleon interactions
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Consolidation of the FieldZEPLIN-III0.01t
LUX0.25t
XENON1000.06t
XENONnT6.0t
PandaX-4t4.0t
XENON1T2.0t
DarkSide-500.04t
DEAP-36003.3t
ArDM0.8t
DarkSide-20k30t
PandaX-II0.5t
LZ7.0t
XMASS0.8t
LXe LAr
now
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DarkSide-20k– scale up DS-50 by factor 400: 30t LAr total
20t fiducial
– focus on high-mass region >400 GeV/c²
– aim for background-free 100 t×y exposure → depleted underground Ar (URANIA+ARIA)→ pulse-shape discrimination → high LY needed→ liquid scintillator n-veto → NEW: LAr n-veto
– start @ LNGS within 2021
Readout by two arrays of grouped SiPMs: 14 m² total
Requirements: – PDE: 45% – Dark Count Rate:
0.1 Hz/mm²
G. Fiorillo @ UCLA-DM 2018Eur. Phys. J. Plus (2018) 133
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PandaX-4t
– to be installed at CJPL-II; scale-up by factor 8
– 4t LXe target with 6×10–48 cm² sensitivity to SI interactions @ 40 GeV/c²
– assembly and commissioning: 2019-2020
Sci. China Phys. Mech. Astron. 62 (2019) 31011
368 PMTs
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LZ – LUX/ZEPLIN
● LZ = LUX+ZEPLIN selected by 2014 US DOE-NSF downselection
● to be installed @ SURF (USA)
● 50× larger than LUX
~10t total LXe mass, 7t active target,
● 494 R11410 PMTs
● spring 2020: first science data
● goal: 2×10–48 cm² @ ~50 GeV/c² after 15 t×y exposure
arXiv:1703.09144
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JCAP 04, 027 (2016)XENONnT
- @ LNGS using existing XENON1T systems(existing µ-veto + new Gd-based n-veto)
- 3x larger than XENON1T5.9t active LXe target ~8.5t total mass
- 494 R11410 PMTs (XENON1T+new)- start science by mid 2019- goal: ~2×10–48 cm² @ ~40 GeV/c²
~135cm
~150cm
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XENON1T Stopped10.Dec 2018, 15:06:04 h
Last recorded event Water shield accessible again
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The ultimate Limit
some results are missing...
„neutrino floor“PRD 89, 023524 (2014)
spin-independent WIMP-nucleon interactions
M. Schumann (Freiburg) – Direct Detection 29
The ultimate Limit
some results are missing...
„neutrino floor“PRD 89, 023524 (2014)
spin-independent WIMP-nucleon interactions
some results are missing...some results are missing...
Interactions from coherent neutrino-nucleus scattering (CNNS) will dominate→ ultimate background for direct detection
JCAP 01, 044 (2014)
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LXe-based
DARWIN The ultimate WIMP Detector
1 ty
20 ty
200 ty
Exposure
DARWIN
darwin-observatory.org
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LXe-based
DARWIN The ultimate WIMP Detector
darwin-observatory.org
Baseline scenario~50t total LXe mass R&D started ~40 t LXe TPC~30 t fiducial mass
260 cm
JCAP 11, 017 (2016)
spin-dependent couplings (n-only)
JCA
P 1
0,
01
6 (
20
15
)
M. Schumann (Freiburg) – Direct Detection 33
LXe: Radon Background WIMP ROI: 1–12 keV interval
XENON1T JCAP 04, 027 (2016)
Strategy XENONnT → DARWIN– avoid Rn by material selection– avoid Rn by detector design– NEW: active Rn removal
– cryogenic distillation XENON1T distillation column installed @ XENON100 → demonstrated reduction factor >27 (@ 95% CL) → dedicated column under development @ Münster
EPJ C 77, 358 (2017)
DARWIN goal:ER background dominatedby solar neutrinos
222Rn factor 100 below XENON1T→ this is the main
background challenge
(DEAP-3600 achieved 0.18 µBq/kg)
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LXe: Krypton Removal
P R E L I M I N A R Y
– DARWIN goal: 0.03 ppt (~ 0.1 × pp-neutrinos)– removal by cryogenic distillation
XENON1T: custom designed distillation column EPJ. C 77, 275 (2017)natKr/Xe = (0.6±0.1) ppt achieved
by novel online distillation→ lowest value in LXe experiments ever
XENON1T column has produced gas sample <0.026 ppt = 2.6×10–14 (90% CL) → DARWIN goal achieved