Overview of Dark Matter searches with liquid nobles
Marcin Kuźniak
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Marcin Kuźniak – LIDINE2019, Manchester
Outline
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Dark matter detection Noble liquid technology Physics landscape
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High mass WIMPs
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Spin-independent
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Spin-dependent
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Low mass WIMPs
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Status of experimental Ar and Xe programs Target complementarity Main challenges moving forward (Biased) selection of new ideas Summary
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Marcin Kuźniak – LIDINE2019, Manchester
DM direct detection signature
Direct detection
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Only through rare interactions with ordinary matter
After the interaction, recoiling nucleus deposits energy (heat,
light, electric charge, ...) in the
detector
100 GeV WIMP
Nuclear recoil spectrum
featureless, ~exponential lower threshold =>more sensitivity natural radioactivity is a background
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astrophysics
detector response
particle/nuclear physics
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Marcin Kuźniak – LIDINE2019, Manchester
Backgrounds
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Marcin Kuźniak – LIDINE2019, Manchester
Liquid noble detectors
Excitation
Heat
Nuclear recoils (NR)
Ar and Xe are used for WIMP detection.
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Ar inexpensive and advantageous for purification and background rejection
Why noble elements?
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High light yield, transparent to their own scintillation Easy to purify and scalable to very high masses (At least) two available detection channels: scintillation and ionization
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Single or dual phase
gas
DarkSide
approach
DEAP
approach
Detect primary scintillation light (S1) from the original event. Ionization charge drifted to high field gas phase region and converted to secondary
scintillation (S2).
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Time projection chamber (TPC): time diff. S2-S1 and top PMTs used to localize event
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Electronic recoil discrimination:
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S2/S1 in Xe
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In Ar PSD on S1 only is superior (S2 still used for position reconstruction)
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Dual phase: better position resolution (up to a few meters detector size) Single phase: higher coverage with photosensors, more scalable, operation
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simplicity, easier to make radiopure
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Marcin Kuźniak – LIDINE2019, Manchester
Pulse shape discrimination (PSD)
Ar singlet and triplet excited states have well separated lifetimes (6ns vs. ~1.5us)
Single phase LAr:
scintillation channel is sufficient for b/g rejection no need for the ionization channel
PMT signal:
Prompt : 0-150ns Late: 150ns-10μs
Neutron (AmBe)
γ(22Na)
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Liquid noble gas experiments
single phase
XMASS
DEAP-3600
Xe
Ar
LUX Xenon1T
ArDM DarkSide-50
LZ
dual phase
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Status and prospects
Allowed 95% CL region for CMSSM, approx. *
* sketched by hand,
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for illustration
No new WIMP detection claims LAr and LXe dominate searches in the spin-independent sector >~2 GeV/c2 Continued search towards the neutrino floor still very well motivated
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see e.g. Roszkowski et al., Rept.Prog.Phys. 81 (2018), 066201
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Status and prospects: high mass
Large exposure
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New limits published ~twice a year Beautiful results from LUX, XENON and PandaX
Roadmap in place for reaching the neutrino floor
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Multiple new results from LAr detectors, reducing Scale-up requires global consolidation
the sensitivity gap
of efforts and R&D
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Status and prospects: low mass
Low threshold
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Leading exclusions from DarkSide-50 and XENON1T (both S2-only) Multiple noble liquid-based and other technologies still in play in different parts of the mass spectrum (SuperCDMS, CRESST, NEWS-G, DAMIC)
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The neutrino floor soon within reach Still much work on low-energy calibration and backgrounds
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Room for exciting R&D and new ideas!
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Spin-dependent limits
PICO-60, Phys. Rev. D 100, 022001 (2019)
XENON1T, Phys. Rev. Lett. 122, 141301 (2019)
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Fluorine based target (PICO-60) remain on the lead for WIMP-proton crosssection
LXe detectors dominate the WIMP-neutron sector
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New low-mass and SD results from LXe
LUX
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Uses prompt scintillation signal consisting of single detected photons exploits the double photoelectron
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emission effect at VUV wavelengths
arXiv:1907.06272v1 arXiv:1907.11485v1
XENON1T
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S2-only analysis 258 days livetime
30% used to inform cuts Limit extracted from the rest
In absence of S1, Z-cut is based on S2 width
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New industry standard: effective field theory
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Allows to more fully explore complementarity between different targets in multiple possible WIMP interaction channels
Multiple papers and formulations available (NREFT, ChiralEFT, ...)
Formalism initially developed for SD searches, and first
employed by LUX in 2016
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P. Klos et al., PRD 88, 083516 (2013)
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LUX, PRL 116, 161302 (2016)
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Then generalized to the SI case and employed by XENON1T for WIMP-pion exclusion in 2019
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M. Hoferichter et al., PRD 94, 063505 (2016)
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XENON1T, PRL 122, 071301 (2019)
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Nuclear form factors available for many targets including LXe, and since recently also for LAr, PRD 99, 055031 (2019)
Codes available online for analysts: WIMPy, ChiralEFT
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XENON1T: WIMP-pion exclusion
Phys. Rev. Lett. 122, 071301 (2019)
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ChiralEFT driven interpretation Generally, many operators and coupling types and dark matter scenarios can be addressed on similar grounds Complementary work to follow soon for LAr experiments
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Other channels
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DM-electron
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Axion-like particles, dark photons: XENON1T
arXiv:1907.11485v1
DarkSide-50 Phys. Rev. Lett. 121, 111303 (2018)
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Boosted DM
So far projections, no published limits
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LAr detectors
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More than 300 scientists from 15 countries and 60 institutions Officially supported by underground labs: LNGS, LSC, and SNOLAB
DarkSide-50
(50 kg, LNGS)
10 kg
100 kg
ArDM (1t, LSC)
1000 kg
DEAP-3600 (3.3t,
SNOLAB)
Global Argon Dark Matter Collaboration formed
DarkSide-20k
(50t, LNGS)
100000 kg
Argo: 400 t
Slide courtesy J. Monroe
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On Sept. 8, 2017 an information session was held at the Canadian Embassy in Rome to announce
the formation of the Global Argon Dark Matter Collaboration, including members from the
Darkside-50, DEAP-3600, ARDM and MiniClean collaborations. The membership totals 350 scientists from 68 institutions in 12 countries and has an immediate objective of a 20,000 kilogram detector called DarkSide-20k to be sited at the Gran Sasso Laboratory in Italy, using argon from an underground source in Colorado, USA, with further removal of the isotope 39Ar at a cryogenic distillation column in Sardinia. The overall objective is a reduction of 39Ar content by a factor of more than 15,000 with a high throughput, which will enable a low-background search for the mysterious dark matter, known to account for most of the matter in the universe, but not yet directly observed. A longer term objective of the collaboration is the creation of a detector with 300,000 kg or more low-radioactivity argon at a future site and technology to be determined. This detector will have the capability of reaching to the so-called "Neutrino floor" created by coherent atmospheric neutrino scattering and will have excellent ability to reject low-energy pp solar neutrino events, through the strong electron discrimination capability of liquid argon, providing unambiguous selection of nuclear recoils from weakly interacting massive dark matter candidates. At the same time, it will also have the ability to perform very precise measurements of higherenergy solar neutrinos such as 7Be, pep, and CNO neutrinos.
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DarkSide-50 low-mass limit
PRL121, 081307 (2018)
S2-only analysis. Ionization-only signal allows sensitive searches for low mass WIMPs: • Two cases: no quenching fluctuations and binomially distributed fluctuations • Background measured at higher energy is extrapolated to low energy
Future improvements require reduction of quenching fluctuation systematic and further background reduction
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DEAP-3600 status
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Detailed backgrounds model based on the first calendar year of data (~2017, open analysis)
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Unprecedentedly low Rn level The best pulse-shape discrimination achieved in LAr
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Collecting blinded data since Jan 2018
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20% left non-blind
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Plan to keep collecting data at least until end of 2020
PRD 100, 022004 (2019)
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DEAP-3600 result and plans
PRD 100, 022004 (2019)
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Leading WIMP exclusion in Ar Acceptance reduced due to cuts against events induced by alpha activity in the neck
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Ongoing development of multivariate analysis expected to recover much of acceptance lost due to neck event cuts
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In parallel, planning for a hardware upgrade
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Other physics papers in preparation
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DarkSide-20k and beyond
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Urania plant for underground argon extraction ARIA facility for chemical purification and isotopic separation
Seruci-0
Key projects also for Argo
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DarkSide-20k LAr veto concept
CERN Neutrino Platform:
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2 almost identical cryostats built for ProtoDUNE 8x8x8 m3 inner volume, 750 t of LAr each Technology and expertise taken from LNG industry Construction time: 37-55 weeks Designed as installable underground
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New approach: atmospheric Ar in ProtoDUNE style large cryostat to provide shielding and active VETO:
ProtoDUNE
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Allows to eliminate Liquid Scintillator Veto New veto is a giant single phase LAr
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detector
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Simplify the overall system complexity and operation Design fully scalable to a 400 tonne
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detector
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LXe detectors
XENON10 (LNGS)
ZEPLIN II (Boulby)
ZEPLIN III (Boulby)
10 kg
100 kg
XENON100 (LNGS)
LUX (250 kg, SURF)
PandaX
(500 kg, CJPL)
XMASS
(0.8t, Kamioka)
1000 kg
XENON1T
(1t, LNGS)
PandaX-4 (4t, CJPL)
XENONnT: (6t, LNGS)
LZ: (7t, SURF)
10000 kg
DARWIN: 50 t
Slide courtesy J. Monroe
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Start in 2020
Sanford lab (SURF), South Dakota
LZ (LUX + ZEPLIN)
10 tons total, 7 tons active, ~5.6 ton fiducial mass
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Limited by elastic scattering of solar pp neutrinos on electrons!
Electronic/nuclear recoil discrimination will be critical to achieve this goal.
Assuming the best factor already achieved by large scale detectors.
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XENONnT
E. Aprile, APS 2019
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E. Aprile, APS 2019
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F. Krueger
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Ar-Xe complementarity
Newstead et al., PRD D 88, 076011 (2013) DARWIN, JCAP 10 (2015) 016
D. Cerdeno, IPPP April 2018
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