Overview of searches with liquid nobles

Marcin Kuźniak [email protected]

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 1 Outline ● Dark matter detection ● Noble liquid technology ● Physics landscape – High mass WIMPs ● Spin-independent ● Spin-dependent – Low mass WIMPs ● Status of experimental Ar and Xe programs ● Target complementarity ● Main challenges moving forward ● (Biased) selection of new ideas ● Summary

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 2 DM direct detection signature

Direct detection

● Only through rare interactions with ordinary matter

● After the interaction, recoiling nucleus deposits energy (heat, 100 GeV WIMP light, electric charge, ...) in the detector

Nuclear recoil spectrum ● featureless, ~exponential ● lower threshold =>more sensitivity ● natural radioactivity is a background astrophysics

detector response

particle/nuclear physics

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 3 Backgrounds

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 4 Liquid noble detectors

Excitation

Heat

Nuclear recoils (NR)

Ar and Xe are used for WIMP detection. ● Ar inexpensive and advantageous for purification and background rejection

Why noble elements? ● 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

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 5 Single or dual phase

DEAP gas DarkSide approach 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).

● Time projection chamber (TPC): time diff. S2-S1 and top PMTs used to localize event ● Electronic recoil discrimination: ● S2/S1 in Xe ● In Ar PSD on S1 only is superior (S2 still used for position reconstruction) ● Dual phase: better position resolution (up to a few meters detector size) ● Single phase: higher coverage with photosensors, more scalable, operation simplicity, easier to make radiopure 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 6 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)

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 7 Liquid noble gas experiments single phase

XMASS

DEAP-3600 Ar Xe LUX Xenon1T ArDM DarkSide-50

LZ

dual phase

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 8 Status and prospects

Allowed 95% CL region for CMSSM, approx. *

* sketched by hand, ● No new WIMP detection claims for illustration ● LAr and LXe dominate searches in the spin-independent sector >~2 GeV/c2 ● Continued search towards the neutrino floor still very well motivated ● see e.g. Roszkowski et al., Rept.Prog.Phys. 81 (2018), 066201 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 9 Status and prospects: high mass Large exposure

● New limits published ~twice a year ● Roadmap in place for reaching the ● Beautiful results from LUX, XENON and PandaX neutrino floor ● Multiple new results from LAr detectors, reducing ● Scale-up requires global consolidation the sensitivity gap of efforts and R&D 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 10 Status and prospects: low mass Low threshold

● Leading exclusions from DarkSide-50 and XENON1T (both S2-only) ● The neutrino floor soon within reach ● Multiple noble liquid-based and other technologies ● Still much work on low-energy calibration still in play in different parts of the mass spectrum and backgrounds (SuperCDMS, CRESST, NEWS-G, DAMIC) ● Room for exciting R&D and new ideas! 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 11 Spin-dependent limits

XENON1T, Phys. Rev. Lett. 122, 141301 (2019) PICO-60, Phys. Rev. D 100, 022001 (2019)

● Fluorine based target (PICO-60) remain on the lead for WIMP-proton cross- section

● LXe detectors dominate the WIMP-neutron sector

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 12 New low-mass and SD results from LXe LUX ● Uses prompt scintillation signal consisting of single detected photons ● exploits the double photoelectron emission effect at VUV wavelengths

arXiv:1907.06272v1

XENON1T arXiv:1907.11485v1 ● 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

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 13 New industry standard: effective field theory ● 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 – P. Klos et al., PRD 88, 083516 (2013) – LUX, PRL 116, 161302 (2016) ● Then generalized to the SI case and employed by XENON1T for WIMP-pion exclusion in 2019 – M. Hoferichter et al., PRD 94, 063505 (2016) – XENON1T, PRL 122, 071301 (2019) ● 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

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 14 XENON1T: WIMP-pion exclusion

Phys. Rev. Lett. 122, 071301 (2019)

● 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

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 15 Other channels ● DM-electron ● -like particles, dark photons: XENON1T arXiv:1907.11485v1

DarkSide-50

Phys. Rev. Lett. 121, 111303 (2018) ● Boosted DM

arXiv:1712.07126 So far projections, no published limits

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 16 LAr detectors 20 10 ● More than 300 scientists 10 kg DarkSide-50 (50 kg, LNGS) from 15 countries and 60 institutions ● Officially supported by 100 kg underground labs: LNGS, LSC, and SNOLAB ArDM (1t, LSC) 2 1000 kg 0 15 DEAP-3600 (3.3t, Global Argon Dark Matter SNOLAB) Collaboration formed

DarkSide-20k 20 20 (50t, LNGS)

100000 kg

Argo: 400 t Slide courtesy J. Monroe 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 17 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 higher- energy solar neutrinos such as 7Be, pep, and CNO neutrinos. 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 18 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 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 19 arXiv:1905.05811 DEAP-3600 status

● Detailed backgrounds model based on the first calendar year of data (~2017, open analysis)

● Unprecedentedly low Rn level

● The best pulse-shape discrimination achieved in LAr

● Collecting blinded data since Jan 2018

● 20% left non-blind

● Plan to keep collecting data at least until end of 2020 PRD 100, 022004 (2019)

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 20 DEAP-3600 result and plans

PRD 100, 022004 (2019)

● Leading WIMP exclusion in Ar

● Acceptance reduced due to cuts against events induced by alpha activity in the neck – Ongoing development of multivariate analysis expected to recover much of acceptance lost due to neck event cuts – In parallel, planning for a hardware upgrade

● Other physics papers in preparation

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 21 DarkSide-20k and beyond

● Urania plant for underground argon Seruci-0 extraction ● ARIA facility for chemical purification and isotopic separation ● Key projects also for Argo

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 22 DarkSide-20k LAr veto concept CERN Neutrino Platform:

● 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

New approach: atmospheric Ar in ProtoDUNE style large cryostat to provide shielding and active VETO: ProtoDUNE

● Allows to eliminate Liquid Scintillator Veto ● New veto is a giant single phase LAr detector ● Simplify the overall system complexity and operation ● Design fully scalable to a 400 tonne detector

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 23 LXe detectors 20 10 XENON10 (LNGS) 10 kg ZEPLIN II (Boulby) ZEPLIN III (Boulby)

100 kg XENON100 (LNGS) LUX (250 kg, SURF) PandaX 20 (500 kg, CJPL) 15 XMASS (0.8t, Kamioka) 1000 kg XENON1T (1t, LNGS) 2 PandaX-4 (4t, CJPL)02 XENONnT: (6t, LNGS) 0 LZ: (7t, SURF)

10000 kg

DARWIN: 50 t Slide courtesy J. Monroe 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 24 Sanford lab (SURF), LZ (LUX + ZEPLIN) Start in 2020 South Dakota

10 tons total, 7 tons active, ~5.6 ton fiducial mass

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 25 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.

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 26 XENONnT

E. Aprile, APS 2019 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 27 E. Aprile, APS 2019 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 28 F. Krueger

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 29 Ar-Xe complementarity

Newstead et al., PRD D 88, 076011 (2013) DARWIN, JCAP 10 (2015) 016

D. Cerdeno, IPPP April 2018

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 30 Ar-Xe complementarity, other scenario

● Many scenarios possible in nature.

● Vanilla WIMP model assumes isospin conservation.

● DEAP-3600 is beginning to explore uncharted territory in the context of isospin-violating DM.

● (Xenon no longer the leading technology to study xenophobic DM.)

JCAP04 (2019) 041 C. E. Yaguna, New Constraints on Xenophobic Dark Matter from DEAP-3600

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 31 Discovery potential

ESPPU Document #97 (input to the European Particle Physics Strategy Update 2018-2020)

● Superior ER rejection in LAr (with PSD) allows to suppress background from elastic scattering of solar neutrinos on electrons ● Zero background paradigm results translates to better 5-sigma discovery sensitivity ● Need for both programs recognized by APPEC, P5, and under consideration for the European Long Range strategy ● Time to start working closer together across collaborations, in the spirit of LIDINE and LRT 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 32 Main challenges moving beyond LZ/XENONnT/DS-20k LXe LAr ● Securing enough ● Very large, highly Xenon efficient, photosensitive surface area ● Rn mitigation ● UAr extraction/storage ● ER rejection ● Scalable and robust ● HV scalability/stability wavelength shifter/light ● Other backgrounds collection approach ● Backgrounds Maximum light yield (i.e. as efficient light collection and detection as possible) greatly improves overall sensitivity (reduces threshold and helps with background mitigation)

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 33 Promising ideas for

● better low-mass sensitivity

● scale-up for better high-mass sensitivity

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 34 Enhancing LXe sensitivity at low mass

● Admixture of low-Z dopant can dramatically increase the sensitivity to low mass WIMPs

● R&D ongoing

● Sensitivity and feasibility studies on LXe mixtures with hydrogen

Lippincott, talk at IDM 2018 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 35 LAr Scintillating Bubble Chamber ● Northwestern ● Queen’s ● Fermilab ● Drexel ● Alberta ● TRIUMF ● PNNL ● UNAM ● IUSB Excitation

Heat

Nuclear recoils ● Combine the ER discrimination of bubble (NR) ● chambers with the event-by-event energy LAr SBC resolution of scintillation detectors ● Aggressive threshold ● Bubble imaging with cameras ● Competitive low-mass WIMP sensitivity ● Light detection with SiPMs ● Advantageous also for CEvNS ● 30g LXe SBC prototype developed at NU ● 10kg prototype to demonstrate scalability and to calibrate ER and NR nucleation ● Start-up funding, finalized design and ongoing fabrication of a LAr SBC probability 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 36 Novel wavelength shifters ● LAr scintillates at 128nm. VUV sensitive SiPMs or/and wavelength shifters are necessary ● Vacuum evaporation of tetraphenyl butadiene costly and non-trivial to scale to >~1000m2 surface area

● Alternatives: – Other evaporated WLS (bis-MSB, p-terphenyl, ...) – Polyethylene naphthalate foil, see MK et al., EPJ C 79:291 (2019), and my LIDINE2019 talk – Distributed WLS: ● ~1000ppm admixture of Xe? D. Rudik’s talk from the morning session ● Nanoparticles? – VUV sensitive devices? ● A lot of activity: Hamamatsu, Sherbrooke/TRIUMF, JPL

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 37 Digital SiPMs Very promising for the future, more development needed to satisfy experimental requirements. University of Sherbrooke: S. Charlebois, J.-F. Pratte innovative 3D digital SiPMs concept (3DdSiPMs) ● CMOS basedDigital SiPMs ● Extremely(U low Sherbrooke) power consumption ● Significant amount of data reduction on a single avalanche photodiode (SPAD) level ● Fast digital output signal with IDs of hit SPAD pixels

CFI review panel: “a game changer technology”

Very high photon detection efficiency, and radiopure.

Independent approach pursued by the group at INFN Torino, see LIDINE2019 talk by R. Kugathasan ALCOR - A Low Power Chip for Optical Sensor Readout

M. Rolo, FEE2018 Jouvence 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 38 PSD against surface events Boulay and Kuzniak, arXiv:1903.00257, see D. Gallagher’s slides from earlier today ● a-decays near detector surfaces are problematic for DM searches ● Multilayer surface coating of TPB and slow scintillator allows very powerful PSD suppression of these background without requirement for position reconstruction ● Concept: add a thin layer of “slow” scintillator so that a energy can never be hidden at TPB interface

Need for position reconstruction greatly reduced.

Useful for low- and high-mass searches, CEvNS

Can mitigate surface events with PSD in large and in small39 detectors!

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 39 Summary ● Many interesting new results and ideas since last LIDINE ● Low-mass region (1-10 GeV/c2) increasingly competitive (LXe S2 only, LAr S2 only, LAr SBC, SuperCDMS). ● Huge progress in interpretation of results with EFT ● Larger detectors still the best strategy for high-mass WIMP searches – LAr: ● Global consolidation of efforts towards DarkSide-20k and the ultimate detector, Argo ● Fruitful synergy with ProtoDUNE/DUNE ● Novel materials to facilitate scale-up ● Rapid growth of the SiPM technology – LXe: ● XMASS contribution of Gd-veto to the XENONnT program ● Successful progression of 2 phase LXe TPCs ● Ongoing R&D for DARWIN ● Exciting times ahead!

29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 40